@article{ClaGaw75,
author = {D. W. Clarke and
P. J. Gawthrop},
keyword = {STC},
cscauthor = {pjg},
title = {A generalised self-tuning regulator {} Simulation of
a generalised self-tuning regulator},
journal = {Electronics Letters},
volume = 11,
number = 2,
year = 1975
}
@article{ClaGaw75a,
author = {D. W. Clarke and
P. J. Gawthrop},
cscauthor = {pjg},
title = {Self-tuning controller},
journal = {IEE Proceedings Part~D: Control Theory and Applications},
volume = 122,
number = 9,
pages = {929-934},
year = 1975,
doi = {10.1049/piee.1975.0252}
}
@article{Gaw77,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {Some interpretations of the self-tuning controller},
journal = {Proceedings IEE},
volume = 124,
number = 10,
pages = {889-894},
year = 1977
}
@article{ClaGaw79,
author = {D. W. Clarke and
P. J. Gawthrop},
cscauthor = {pjg},
title = {Self-tuning {C}ontrol},
journal = {IEE Proceedings Part~D: Control Theory and Applications},
volume = 126,
number = 6,
pages = {633-640},
year = 1979,
doi = {10.1049/piee.1979.0145}
}
@article{Gaw80,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {On the stability and convergence of a self-tuning
controller},
journal = {Int. J. Control},
volume = 31,
number = 5,
pages = {973-998},
year = 1980
}
@article{Gaw80a,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {A comment on ``Self-tuning pole/zero assignment
regulators''},
journal = {Int. J. Control},
volume = 31,
number = 5,
pages = {999-1002},
year = 1980
}
@article{Gaw80b,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {Hybrid self-tuning control},
journal = {Proc. IEE},
volume = 127,
number = 5,
pages = {229-236},
year = 1980
}
@article{ClaGaw81,
author = {D. W. Clarke and
P. J. Gawthrop},
cscauthor = {pjg},
title = {Implementation and application of microprocessor-based
self-tuners},
journal = {Automatica},
volume = 17,
number = 1,
pages = {233-244},
year = 1981,
abstract = {
The implementation of a class of self-tuning controllers using a
portable microcomputer system is described. The self-tuning control
theory is shown to provide a variety of control objectives such as
model-reference, optimal Smith prediction and the minimization of a
general k-step-ahead cost-function. Hardware and software details of
the portable computer, SESAME, are presented with particular reference
to the use of a new high-level language, Control Basic. Studies of the
application of self-tuning to the control of room-temperature, acid
neutralization, and batch chemical reactors in industry are outlined.
},
doi = {10.1016/0005-1098(81)90098-4}
}
@article{GawLim82,
author = {P. J. Gawthrop and
K. W. Lim},
cscauthor = {pjg},
title = {On the robustness of self-tuning controllers},
journal = {Proc. IEE},
volume = {129 ptD},
pages = {21-29},
year = 1982
}
@article{Gaw82b,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {A continuous-time approach to discrete-time
self-tuning control},
journal = {Optimal Control: Applications and Methods},
volume = 3,
number = 4,
pages = {399-414},
year = 1982
}
@article{ProGawJac83,
author = {Proudfoot, C.G. and Gawthrop, P.J. and Jacobs, O.L.R.},
journal = {Control Theory and Applications, IEE Proceedings D},
title = {Self-tuning PI control of a pH neutralisation process},
year = 1983,
month = {september },
volume = 130,
number = 5,
pages = {267 -272},
abstract = {The paper shows how a certain self-tuning algorithm can be interpreted as a self-tuning PI controller, and this algorithm has been successfully tested on a full-scale pH neutralisation process. Extended trials showed that although this process could be well controlled by a fixed parameter PI controller, the self-tuning algorithm could easily find suitable fixed parameter values for the controller, whereas human operators found the tuning difficult, if not impossible.},
keywords = {PI control;pH neutralisation process;self-tuning;pH control;self-adjusting systems;two-term control;},
doi = {10.1049/ip-d:19830046},
issn = {0143-7054}
}
@article{ClaGaw84,
author = {D. W. Clarke and
P. J. Gawthrop},
cscauthor = {pjg},
title = {Comments on: ``On adaptive minimum variance regulation
for nonminimum phase plants''},
journal = {Automatica},
volume = 20,
number = 2,
pages = 261,
year = 1984
}
@article{Gaw84a,
author = {Gawthrop, P.J.},
journal = {Control Theory and Applications, IEE Proceedings D},
title = {Parameter estimation from noncontiguous data},
year = 1984,
volume = 131,
number = 6,
pages = {261-266},
abstract = {A `linear-in-the-parameters¿ representation is derived for a data set formed by concatenating a number of input-output data records which, although arising from the same system, are not contiguous in time. As well as parameters describing the system, further `splicing parameters¿ arise from the discontinuities in the concatenated data records at the joins. This representation gives rise to a method of `data splicing¿ which enables system parameters to be recursively identified from the concatenated data records. The method is particularly useful when each individual data record is not, by itself, sufficient to identify the system parameters. The method is developed for noise-free differential equation models, but the basic principles are more widely applicable. An illustrative example is given.},
keywords = {parameter estimation;discontinuities;input-output data records;noise-free differential equation models;parameter estimation;splicing parameters},
doi = {10.1049/ip-d:19840044},
issn = {0143-7054}
}
@article{Gaw84d,
author = {Gawthrop, P. J.},
title = {Parametric Identification of Transient Signals},
volume = 1,
number = 2,
pages = {117-128},
year = 1984,
doi = {10.1093/imamci/1.2.117},
abstract = {The state-variable filter method of continuous-time parameter identification using a discrete-time identifier is extended to be applicable to signals composed of a transient response generated by a class of unforced nonlinear systems to which has been added a constant offset. The results are illustrated by estimating some hydrodynamic coefficients of a ship from free decay data; and some implications for self-tuning control are discussed.},
journal = {IMA Journal of Mathematical Control and Information}
}
@article{GawNih85,
title = {Identification of time delays using a polynomial identification method},
journal = {Systems and Control Letters},
volume = 5,
number = 4,
pages = {267-271},
year = 1985,
issn = {0167-6911},
doi = {10.1016/0167-6911(85)90020-9},
author = {P.J. Gawthrop and M.T. Nihtilä},
keywords = {Time-delay, Continuous-time identification, Non-linear identification},
abstract = {An algorithm for the exact least-squares identification of an approximate continuous-time time-delay system is derived and its operation verified by simulation.}
}
@article{Gaw85e,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {Computer-Aided Learning of Signal Theory},
journal = {Trans. Inst. Measurement and Control},
volume = 7,
number = 2,
pages = {61-65},
year = 1985
}
@article{Gaw86,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {Self-tuning {PID} controllers: Algorithms and
implementation},
journal = {IEEE Transactions on Automatic Control},
volume = {AC-31},
number = 3,
pages = {201-209},
year = 1986
}
@article{Gaw86b,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {Self-tuning control --- an overview},
journal = {EI Technology},
volume = 1,
pages = {16-19},
year = 1986
}
@article{Gaw87b,
author = {Gawthrop, P. J.},
title = {Robust stability of a continuous-time self-tuning controller},
journal = {International Journal of Adaptive Control and Signal Processing},
volume = 1,
number = 1,
publisher = {Wiley Subscription Services, Inc., A Wiley Company},
issn = {1099-1115},
doi = {10.1002/acs.4480010104},
pages = {31--48},
keywords = {Self-tuning, Adaptive, Stability, Robustness},
year = 1987,
abstract = {A continuous-time self-tuning controller, based on the well-known discrete-time generalized minimum-variance self-tuning controller, is introduced. Using input—output stability methods, frequency domain conditions are derived which ensure L∞ stability in the face of multiplicative process perturbations. The analysis is illustrated using an example of Rohrs et al.}
}
@article{LeaGaw87,
author = {Leary, J.J. and Gawthrop, P.J.},
cscauthor = {pjg},
journal = {Control Theory and Applications, IEE Proceedings D},
title = {Process fault detection using constraint suspension},
year = {1987},
month = {july },
volume = {134},
number = {4},
pages = {264 -271},
abstract = {In the paper the authors describe two tools for use in an intelligent fault-detection system. The first tool is a method for fault localisation, called constraint suspension, which helps us find and identify the parts suspension, which helps us find and identify the parts of the process which are responsible for any inconsistencies in the measurements. The second tool gives us a flexible framework in which we can build a software model of the process in terms of hierarchies of component parts or objects, it is called object orientation. We use these tools to describe algorithms for automatic fault detection in a physical process plant. The algorithms are tested on a simulation of a liquid level control system.},
keywords = {constraint suspension;fault detection;intelligent fault-detection system;liquid level control system;object orientation;parts suspension;process control;software model;control system analysis;fault location;level control;process computer control;},
doi = {10.1049/ip-d:19870044},
issn = {0143-7054}
}
@article{GawKha88,
author = {P. J. Gawthrop and
M. Kharbouch},
cscauthor = {pjg},
title = {Two-loop self-tuning cascade control},
journal = {Proc. IEE Pt.D},
volume = {135},
number = 4,
pages = {232-238},
year = 1988,
pdf = {../../Publications/csc1988/GawKha88.pdf}
}
@article{GawKouRob88,
author = {P. J. Gawthrop and
A. Kountzeris and
J. B. Roberts},
cscauthor = {pjg},
title = {Parametric identification of non-linear roll motion
from forced roll data},
journal = {Journal of Ship Research},
volume = 32,
number = 2,
pages = {101-111},
year = 1988,
pdf = {../../Publications/csc1988/GawKouRob88.pdf}
}
@article{DemGaw88,
author = {H. Demircioglu and
P. J. Gawthrop},
cscauthor = {pjg},
title = {Continuous-time relay self-tuning control},
journal = {Int. J. Control},
volume = 47,
number = 4,
pages = {1061-1080},
year = 1988
}
@article{GawNihBes89,
author = {P. J. Gawthrop and
M. T. Nihtila and
A. Besharati-Rad},
cscauthor = {pjg},
title = {Recursive parameter estimation of continuous-time
systems with unknown time delay},
journal = {{C-TAT}},
volume = 15,
number = 3,
pages = {227--248},
year = 1989
}
@article{KouRobGaw89,
author = {A. Kountzeris and J. B. Roberts and P. J. Gawthrop},
cscauthor = {pjg},
title = {Estimation of Ship Roll parameters from Motion
in Irregular seas},
journal = {Royal Institution of Navel Architects},
year = 1989
}
@article{Gaw90a,
author = {Gawthrop, P. J.},
title = {Robust stability of multi-loop continuous time self-tuning controllers},
journal = {International Journal of Adaptive Control and Signal Processing},
volume = 4,
number = 5,
publisher = {Wiley Subscription Services, Inc., A Wiley Company},
issn = {1099-1115},
doi = {10.1002/acs.4480040504},
pages = {359--382},
keywords = {Adaptive control, Robust stability, Multivariable control},
year = 1990,
abstract = {The results of an earlier paper concerning global robustness of single-loop self-tuning controllers are extended to include multiple self-tuning controllers operating in a multiple-interacting-loop environment. The robust stability is shown to depend on the singular value loci of a certain transfer function matrix. The need for control weighting to ensure global robust stability is emphasized.}
}
@article{GawMirLi90,
author = {P. J. Gawthrop and
H. Mirab and
X. Li},
cscauthor = {pjg},
title = {Robot Model Validation},
journal = {Transactions of the Institute of Measurement and Control},
volume = 12,
number = 4,
month = {May},
pages = {197--207},
year = 1990
}
@article{GawNom90,
author = {P. J. Gawthrop and P. E. Nomikos},
cscauthor = {pjg},
title = {Automatic tuning of commercial PID controllers
for single-loop and multi-loop applications},
journal = {IEEE Control Systems Magazine},
volume = 10,
number = 1,
month = {January},
pages = {34-42},
year = 1990,
pdf = {../../Publications/csc1990/GawNom90.pdf}
}
@article{GawSba90,
author = {P. J. Gawthrop and
D. G. Sbarbaro},
cscauthor = {pjg},
title = {Stochastic approximation and Multilayer perceptrons:
The gain back-propagation Algorithm},
journal = {Complex System Journal},
volume = 4,
pages = {51--74},
year = 1990,
abstract = {A standard general algorithm, the stochastic approximation algorithm of Albert and Gardner [1], is applied in a new context to compute the weights of a multilayer perceptron network. This leads to a new algorithm, the gain backpropagation algorithm, which is related to, but significantly different from, the standard backpropagation algorithm [2]. Some simulation examples show the potential and limitations of the proposed approach and provide comparisons with the conventional backpropagation algorithm.}
}
@article{GawNomSmi90,
author = {P. J. Gawthrop and
P. Nomikos and
L. Smith},
cscauthor = {pjg},
title = {Adaptive temperature control of industrial processes:
A comparative survey},
journal = {Proc. IEE Pt.D},
volume = 137,
number = 3,
pages = {137--144},
year = 1990,
pdf = {../../Publications/csc1990/GawNomSmi90.pdf}
}
@article{Gaw91,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {Bond Graphs: A representation for Mechatronic Systems},
journal = {Mechatronics},
pages = {127--156},
month = {April},
volume = 1,
number = 2,
year = 1991,
pdf = {../../Publications/csc1991/Gaw91.pdf},
abstract = {
A tutorial introduction to the use of bond graphs in modelling
mechatronic systems is given. Four illustrative examples of increasing
complexity are given, culminating in a two link robotic arm with
flexible drives. The role of symbolic algebra techniques in this
context is emphasized and it is suggested that the marriage of bond
graphs and symbolic techniques provides the basis of computer-based
support tools for the analysis and design of mechatronic systems.
},
url = {http://dx.doi.org/10.1016/0957-4158(91)90040-H}
}
@article{DemGaw91,
author = {H. Demircioglu and P. J. Gawthrop},
cscauthor = {pjg},
title = {Continuous-time Generalised Predictive Control},
journal = {Automatica},
volume = 27,
number = 1,
pages = {55--74},
month = {January},
year = 1991,
url = {http://dx.doi.org/doi:10.1016/0005-1098(91)90006-N},
pdf = {../../Publications/csc1991/DemGaw91.pdf}
}
@article{RobKouGaw91,
author = {J. B. Roberts and A. Kountzeris and P. J. Gawthrop},
cscauthor = {pjg},
title = {Parametric Identification Techniques for Roll Decrement Data},
journal = {Int. Shipbuilding Progr.},
volume = 38,
number = 415,
pages = {271--293},
year = {1991}
}
@article{PonGaw91,
author = {J. W. Ponton and P. J. Gawthrop},
cscauthor = {pjg},
title = {Systematic construction of dynamic models for phase equilibrium
processes},
journal = {Computers chem Engng},
volume = 15,
number = 12,
pages = {803-808},
abstract = {
A systematic approach to constructing dynamic models involving phase equilibrium is presented.
The view appears to be widely held that the dynamic modelling of VLE
systems invariably leads to an "index problem". We show that this in
general is not the case if an appropriate model formulation is
used. This is provided by our systematic procedure.
Index problems do in general occur when a state variable is
constrained by an implied control system. Some properties of such
systems are discussed and it is shown that it may not in practice be
useful to attempt the solution of intractable index problems, as these
may differ substantially from the behaviour of an achievable control
system.
},
url = {http://dx.doi.org/10.1016/0098-1354(91)80026-R},
year = 1991,
pdf = {../../Publications/csc1991/PonGaw91.pdf}
}
@article{DemGaw92,
author = {H. Demircioglu and
P. J. Gawthrop},
cscauthor = {hd,pjg},
title = {Multivariable Continuous-time Generalised Predictive Control},
journal = {Automatica},
volume = 28,
number = 4,
pages = {697--713},
weighting = {1(0)/2},
ccode = {11},
keywords = {},
year = 1992,
doi = {10.1016/0005-1098(92)90031-A}
}
@article{GawJonMac92b,
author = {P. J. Gawthrop and
R. W. Jones and
S. A. MacKenzie},
cscauthor = {pjg,rwj,sam},
title = {Identification of partially-known systems},
journal = {Automatica},
volume = 28,
number = {4},
pages = {831--836},
weighting = {1(2)/3},
ccode = {11},
keywords = {},
year = 1992,
abstract = {
The concepts of partially-known system identification are introduced
and the advantages of a method whereby process information can be
utilized in a linear transfer function representation of the system
are highlighted and discussed. In particular, an algorithm for
identifying a single unknown physical system parameter associated
with a linear system is given. It is assumed that the system is
polynomial (as opposed to linear) in the physical parameter. The
Bond graph representation is used as the basis for deriving a
system-dependent algorithm for each partially-known system. The
method is illustrated by simulated examples. },
pdf = {../../Publications/csc1992/GawJonMac92.pdf},
doi = {10.1016/0005-1098(92)90046-I}
}
@article{GawSmi92a,
author = {P. J. Gawthrop and
L. Smith},
cscauthor = {pjg},
title = {Causal augmentation of bond graphs with algebraic loops},
journal = {Journal of the Franklin Institute},
volume = 329,
number = 2,
pages = {291--303},
weighting = {},
ccode = {1(1)/2},
keywords = 11,
year = 1992,
doi = {10.1016/0016-0032(92)90035-F},
abstract = {An algorithm for the causal augmentation of bond graphs with
algebraic loops is given. Unlike previous algorithms, this involves
bond graph rather than equation manipulation. A number of
illustrative examples are given.},
pdf = {../../Publications/csc1992/GawSmi92.pdf}
}
@article{HunSbaZbiGaw92,
author = {K. J. Hunt and
R. Zbikowski and
D. Sbarbaro and
P. J. Gawthrop},
cscauthor = {kjh,pjg},
title = {Neural Networks for Control Systems---A survey},
journal = {Automatica},
volume = {28},
number = {6},
pages = {1083--1112},
weighting = {2(2)/4},
ccode = {11},
keywords = {},
year = 1992,
abstract = {
This paper focuses on the promise of artificial neural networks in the
realm of modelling, identification and control of nonlinear
systems. The basic ideas and techniques of artificial neural networks
are presented in language and notation familiar to control
engineers. Applications of a variety of neural network architectures
in control are surveyed. We explore the links between the fields of
control science and neural networks in a unified presentation and
identify key areas for future research.
},
pdf = {../../Publications/csc1992/HunSbaZbiGaw92.pdf},
doi = {10.1016/0005-1098(92)90053-I}
}
@article{GawJezJon93,
author = {P. J. Gawthrop and J. Je{z}ek and
R. W. Jones and I. Sroka},
cscauthor = {pjg},
title = {Grey-box model identification},
journal = {Control-Theory and Advanced Technology},
volume = 9,
number = 1,
pages = {139--157},
year = 1993
}
@article{JonGaw93a,
author = {R.W. Jones and P.J. Gawthrop},
title = {Inferential control using nonlinear model-based observer control},
journal = {Control Engineering Practice},
year = 1993,
volume = 1,
number = 1,
pages = {151 - 156},
month = {February}
}
@article{GawJon93,
author = {P.J. Gawthrop and R.W. Jones},
title = {Bond-Graph-based adaptive control},
journal = {Control Engineering Practice},
year = 1993,
volume = 1,
number = 6,
pages = {67-72},
month = {December}
}
@article{Gaw95c,
title = {Physical model-based control: A bond graph approach},
journal = {Journal of the Franklin Institute},
volume = {332},
number = {3},
pages = {285-305},
year = {1995},
issn = {0016-0032},
doi = {10.1016/0016-0032(95)00044-5},
author = {Peter J. Gawthrop},
abstract = {A bond graph representation of model-based observer control is introduced and shown to provide a convenient framework for the design of controllers in the physical domain. The approach is illustrated by a series of examples and the robustness of the method is investigated by simulation.}
}
@article{RobBalGaw95,
title = {Design and implementation of a bond-graph observer for robot control},
journal = {Control Engineering Practice},
volume = 3,
number = 10,
pages = {1447-1457},
year = 1995,
issn = {0967-0661},
doi = {10.1016/0967-0661(95)00148-N},
author = {D.W. Roberts and D.J. Ballance and P.J. Gawthrop},
keywords = {Robots, modelling, bond graphs, state estimation, position control},
abstract = {In robotics, high-precision measurements of link positions are available for feedback control but tachometer measurements of link velocities are often severely contaminated by noise. This paper presents the use of a bond-graph model-based nonlinear observer to estimate the velocities in the control of an experimental two-link manipulator. A significant advantage of this approach is that the observer software may be written automatically from the bond-graph observer representation. Results are presented in simulation form, and for practical implementation on the experimental arm.}
}
@article{GawPon96,
author = {P. J. Gawthrop and J. W. Ponton},
cscauthor = {pjg},
title = {Improved Control using Dynamic Process Models},
journal = {Chemical Engineering Research and Design},
weighting = {},
ccode = {},
volume = 74,
number = {A1},
pages = {63--69},
issn = {0263-8762},
month = {Jan},
year = {1996}
}
@article{SbaHunGaw96,
author = {D. Sbarbaro and K. J. Hunt and P. J. Gawthrop},
cscauthor = {kjh,pjg},
title = {Designing nonlinear controllers using
connectionist networks},
journal = {Mathematics and Computers in Simulation},
year = {1996},
volume = {40},
issn = {0378-4754},
pages = {657--663},
pdf = {../../Publications/csc1996/SbaHunGaw96.pdf}
}
@article{GawJonSba96,
title = {Emulator-based control and internal model control: Complementary approaches to robust control design},
journal = {Automatica},
volume = {32},
number = {8},
pages = {1223-1227},
year = {1996},
issn = {0005-1098},
doi = {10/0005-1098(96)00059-3},
author = {Peter J. Gawthrop and Richard W. Jones and Daniel G. Sbarbaro},
keywords = {Control system analysis, internal model control},
abstract = {Two alternative approaches to controller design, the internal model control (IMC) of Morari and Zafiriou [Morari, M. and E. Zafiriou (1989). Robust Process Control. Prentice Hall, Englewood Cliffs, NJ] and the emulator-based control (EBC) of Gawthrop [Gawthrop, P. J. (1987). Continuous-time Self-tuning Control. Vol. 1: Design, Engineering Control Series. Research Studies Press, Lechworth, U.K.] (based on the generalized minimum variance control of Clarke and Gawthrop [Clarke, D. W. and P. J. Gawthrop (1975). Self-tuning controller. Proc. IEE, 122(9), 929–934. Clarke, D. W. and P. J. Gawthrop (1979). Self-tuning control. Proc. IEE, 126(6), 640–6333. Gawthrop, P. J. (1977). Some interpretations of the self-tuning controller. Proc. IEE, 124(10), 889–894]) are shown to differ only superficially in approach and notation. This result provides a link between robust control based on IMC and adaptive control based on EBC.}
}
@article{CosGaw97,
title = {Physical-Model Based Control: Experiments with a Stirred-Tank Heater},
journal = {Chemical Engineering Research and Design},
volume = 75,
number = 3,
pages = {361-370},
year = 1997,
note = {Particle Processing},
issn = {0263-8762},
doi = {10.1205/026387697523679},
author = {D.J. Costello and P.J. Gawthrop},
keywords = {state estimation, model-based control, partially-known systems},
abstract = {In the pursuit of generic methods, control theory has become separated from its prime objective: the control of physical systems. These generic techniques have a wide range of applications yet do not easily allow inclusion of system specific information into the control design. There are two important categories for which the inclusion of system-specific information is important: partially-known systems and non-linear systems. Physical-Model Based Control (PMBC) is a novel approach to using such system-specific information. The objective of this paper is to demonstrate the experimental application of PMBC to a partiallyknown nonlinear system. In so doing, the performance of the PMBC method is evaluated, and it is demonstrated how process and control engineering insights can be combined within this PMBC framework to yield a novel system-specific control algorithm.}
}
@article{GawBal97,
author = {Peter J. Gawthrop and Donald J. Ballance},
cscauthor = {pjg,djb},
title = {Symbolic Algebra and Physical-Model-Based Control},
journal = {Computing and Control Journal},
volume = 8,
number = 2,
month = {April},
pages = {70-76},
issn = {0956-3385},
year = 1997,
abstract = {In order to achieve the best possible control of a
particular system, it is clear that as much information
about the system as possible should be used when designing
the controller. This leads to a controller specifically
tailored to the system being controlled. Unfortunately, this
is expensive in terms of design time and expertise, and a
number of approaches have been suggested to overcome this
problem. The approach taken by physical-model-based control
is to model the system in a generic manner and then
automatically design the controller based on this
model. This process requires symbolic algebra to enable the
controller to be designed},
pdf = {../../Publications/csc1997/GawBal97.pdf}
}
@article{Gaw98a,
author = {Peter J. Gawthrop},
cscauthor = {pjg},
title = {Physical Interpretation of Inverse Dynamics using
Bond Graphs},
journal = {The Bond Graph Digest},
year = 1998,
volume = 2,
number = 1,
month = {January},
pages = {23pp}
}
@article{JohHunGaw98,
author = {T. A. Johansen and K. J. Hunt
and P. J. Gawthrop and H. Fritz},
cscauthor = {kjh,pjg},
title = {Off-equilibrium linearisation and design of gain scheduled
control with application to vehicle speed control},
journal = {Control Engineering Practice},
year = {1998},
volume = {6},
number = {2},
pages = {167--180},
abstract = {In conventional gain-scheduled control design,
linearisation of a time-invariant nonlinear system and local control
design for the resulting set of linear time-invariant systems is
performed at a set of equilibrium points. Due to its validity only
near equilibrium, such a design may result in poor transient
performance. To resolve this problem, one can base the control design
on a dynamic linearisation about some nominal trajectory. However, a
drawback with this approach is that control design for the resulting
linear time-varying system is in general a difficult problem. In this
paper it is suggested that linearisation and local controller design
should be carried out not only at equilibrium states, but also in
transient operating regimes. It is shown that this results in a set of
time-invariant linearisations which, when they are interpolated, form
a close approximation to the time-varying system resulting from
dynamic linearisation. Consequently, the transient performance can be
improved by increasing the number of linear time-invariant
controllers. The feasibility of this approach, and possible
improvements in transient performance, are illustrated with results
from an experimental vehicle speed-control application. },
pdf = {../../Publications/csc1998/JohHunGaw98.pdf}
}
@article{GawDemSil98,
author = {Gawthrop, P.J. and Demircioglu, H. and Siller-Alcala, I.I.},
journal = {Control Theory and Applications, IEE Proceedings -},
title = {Multivariable continuous-time generalised predictive control: a state-space approach to linear and nonlinear systems},
year = 1998,
month = {may},
volume = 145,
number = 3,
pages = {241 -250},
abstract = {The multivariable continuous-time generalised predictive controller (CGPC) is recast in a state-space form and shown to include generalised minimum variance (GMV) and a new algorithm, predictive GMV (PGMV) as special cases. Comparisons are drawn with the exact linearisation methods of nonlinear control, and it is noted that, unlike the transfer function approach, the state-space approach extends readily to the nonlinear case. The resulting state space design algorithms are conceptually and algorithmically simpler than the corresponding transfer function based versions and have been realised as a freely available Matlab tool-box},
keywords = {CGPC;Matlab tool-box;PGMV;exact linearisation methods;generalised minimum variance;linear systems;multivariable continuous-time generalised predictive control ;nonlinear control;nonlinear systems;predictive GMV;state space design algorithms;state-space approach;transfer function based versions;multivariable control systems;nonlinear control systems;predictive control;state-space methods;},
doi = {10.1049/ip-cta:19982045},
issn = {1350-2379}
}
@article{Gaw99a,
author = {P. J. Gawthrop},
cscauthor = {pjg},
title = {Thermal Modelling using Mixed Energy and Pseudo Bond Graphs},
journal = {Proceedings of the Institution of Mechanical Engineers Part I:
Journal of Systems and Control Engineering},
year = 1999,
volume = 213,
number = 3,
month = {June},
pages = {201--216},
abstract = {Pseudo and true Bond Graphs have been seen as competing
approaches to modelling thermodynamic systems. This paper provides a
simple mechanism for mixing the two approaches to obtain the best
features of each. In so doing, an alternative and more accessible
approach to thermodynamic modelling than that provided by classical
texts is given.},
pdf = {../../Publications/csc1999/Gaw99a.pdf},
doi = {10.1243/0959651991540089}
}
@article{RonArsGaw99,
class = {Intermittent},
author = {E. Ronco and T. Arsan and P. J. Gawthrop},
cscauthor = {pjg},
title = {Open-Loop Intermittent Feedback Control: Practical
Continuous-time {GPC}},
journal = {IEE Proceedings Part~D: Control Theory and Applications},
month = {September},
volume = 146,
number = 5,
pages = {426--434},
year = 1999,
abstract = {A conceptual, and practical difficulty with the
continuous-time generalised predictive controller is solved
by replacing the continuously moving horizon by an
intermittently moving horizon. This allows slow optimisation
to occur concurrently with a fast control action. Some
nonlinear simulations illustrate the potential of this
approach.},
doi = {10.1049/ip-cta:19990504}
}
@article{CheBalGaw99e,
author = {W.-H. Chen and D. J. Ballance and P. J. Gawthrop and J. J.
Gribble and J. O'Reilly},
cscauthor = {wc,djb,pjg,jjg,jor},
title = {Nonlinear {PID} Predictive Controller},
year = 1999,
journal = {IEE Proceedings Part~D: Control Theory and Applications},
volume = 146,
number = 6,
month = {November},
pages = {603--611},
abstract = {A new class of nonlinear PID controllers are derived for
nonlinear systems using a nonlinear generalised predictive
control (NGPC) approach. First, the disturbance decoupling
ability of the NGPC is discussed. For a nonlinear system
where the disturbance cannot be decoupled, a nonlinear
observer is designed to estimate the offset. By selecting
the nonlinear gain function in the observer, it is shown
that the closed-loop system under optimal generalised
predictive control with the nonlinear observer is
asymptotically stable. It is pointed out that this composite
controller is equivalent to a nonlinear controller with
integral action. As a special case, for a nonlinear system
with a low relative degree, the proposed nonlinear
controller reduces to a nonlinear PI or PID predictive
controller, which consists of a nonlinear PI or PID
controller and a prediction controller. The design method is
illustrated by an example nonlinear mechanical system},
pdf = {../../Publications/csc1999/CheBalGaw99e.pdf}
}
@article{NgwGaw99,
author = {Roger F Ngwompo and Peter J Gawthrop},
cscauthor = {pjg},
title = {Bond Graph Based Simulation of Nonlinear Inverse Systems
Using Physical Performance Specifications},
journal = {Journal of the Franklin Institute},
year = 1999,
month = {November},
volume = 336,
number = 8,
pages = {1225--1247},
abstract = {Analysis and simulation of non-linear inverse systems
are sometimes necessary in the design of control systems particularly
when trying to determine an input control required to achieve some
predefined output specifications. But unlike physical systems which
are proper, the inverse systems are very often improper leading to
numerical problems in simulation as their models sometimes have a high
index when written in the form of differential-algebraic equations
(DAE). This paper provides an alternative approach whereby performance
specifications and the physical system are combined within a single
bond graph leading to a greatly simplified simulation problem.},
pdf = {../../Publications/csc1999/NgwGaw99.pdf},
doi = {10.1016/S0016-0032(99)00032-0}
}
@article{RonGaw99,
author = {E. Ronco and P. J. Gawthrop},
cscauthor = {pjg},
title = {Incremental polynomial model-controller network:
A self-organising nonlinear controller},
journal = {IEE Proceedings Part~D: Control Theory and Applications},
month = {November},
volume = 146,
number = 6,
pages = {527--543},
year = 1999,
abstract = {An `incremental polynomial model-controller network'
(IPMCN) is introduced. Smooth control switching is obtained
from the use of odd polynomial controllers. The
decomposition of the operating space, together with the
construction of the network, is achieved on-line while
controlling the system. The performance and robustness of
this scheme are illustrated through various simulations. },
pdf = {../../Publications/csc1999/RonGaw99.pdf}
}
@article{CheBalGaw00,
author = {W.-H. Chen and D. J. Ballance and P. J. Gawthrop
and John O'Reilly},
cscauthors = {wc,djb,pjg,jor},
title = {A Nonlinear Disturbance Observer for Robotic Manipulators},
year = 2000,
journal = {IEEE Transactions on Industrial Electronics},
volume = 47,
number = 4,
month = {August},
pages = {932-938},
abstract = {A new nonlinear disturbance observer (NDO) for
robotic manipulators is derived in this
paper. The global exponential stability of the
proposed disturbance observer (DO) is guaranteed
by selecting design parameters, which depend on
the maximum velocity and physical parameters of
robotic manipulators. This new observer
overcomes the disadvantages of existing DOs,
which are designed or analyzed by linear system
techniques. It can be applied in robotic
manipulators for various purposes such as
friction compensation, independent joint
control, sensorless torque control and fault
diagnosis. The performance of the proposed
observer is demonstrated by the friction
estimation and compensation for a two-link
robotic manipulator. Both simulation and
experimental results show the NDO works well},
pdf = {../../Publications/csc2000/CheBalGaw00.pdf}
}
@article{GawRon00b,
author = {Peter J. Gawthrop and Eric Ronco},
cscauthors = {pjg},
title = {Estimation and Control of Mechatronic Systems
Using Sensitivity Bond Graphs},
journal = {Control Engineering Practice},
year = 2000,
volume = 8,
number = 11,
month = {November},
pages = {1237--1248},
abstract = { A new bond graph framework for sensitivity theory is
applied to model-based predictive control, state estimation, and
parameter estimation in the context of physical systems. The
approach is illustrated using a nonlinear mechatronic system.},
pdf = {../../Publications/csc2000/GawRon00b.pdf},
doi = {10.1016/S0967-0661(00)00062-9}
}
@article{Gaw00c,
author = {Peter J Gawthrop},
title = {Sensitivity Bond Graphs},
journal = {Journal of the Franklin Institute},
year = {2000},
volume = 337,
number = 7,
month = {November},
pages = {907-922},
abstract = { A sensitivity bond graph, of the same structure as the
system bond graph, is shown to provide a simple and effective method
of generating sensitivity functions of use in optimisation. The
approach is illustrated in the context of partially-known system
parameter and state estimation.},
pdf = {../../Publications/csc2000/Gaw00c.pdf},
doi = {10.1016/S0016-0032(00)00052-1}
}
@article{Gaw00d,
author = {Peter J Gawthrop},
title = {Physical Interpretation of Inverse Dynamics
using Bicausal Bond Graphs},
journal = {Journal of the Franklin Institute},
year = 2000,
volume = 337,
number = 6,
pages = {743-769},
abstract = {A physical interpretation of the inverse dynamics of
linear and nonlinear systems is given in terms of the bond graph of
the inverse system. It is argued that this interpretation yields
physical insight to guide the control engineer.
Examples are drawn from both robotic and process systems.},
pdf = {../../Publications/csc2000/Gaw00d.pdf},
doi = {10.1016/S0016-0032(00)00051-X}
}
@article{WanGaw01,
author = {Liuping Wang and Peter Gawthrop},
title = {On the estimation of continuous time transfer functions},
journal = {International Journal of Control},
volume = 74,
number = 9,
pages = {889--904},
year = 2001,
publisher = {Taylor Francis},
doi = {10.1080/00207170110037894},
abstract = { This paper proposes a state variable filter approach to continuous time system identification. Two topics are studied in the paper. The first topic is related to the choice of state variable filters. The strategy we adopt is to adjust the time constants of the state variable filters so that a prediction error criterion is minimized. As a result, the estimated model reaches a balance between bias and variances shown by a simulation example. The second topic is related to the choice of model structure. We extend a multiple model estimation algorithm, developed using UD factorization, to continuous time sysem identification. The estimation algorithm generates a set of candidate models, among which the 'best' model structure is found. A simulation example is used to demonstrate the efficacy of the proposed procedure, and an industrial case study on a food cooking extrusion process is given to illustrate the applicability of the algorithm. }
}
@article{GawRon02,
author = {Peter J Gawthrop and Eric Ronco},
title = {Predictive Pole-placement Control with Linear Models},
journal = {Automatica},
pages = {421-432},
year = 2002,
month = {March},
volume = 38,
number = 3,
abstract = {The predictive pole-placement control method introduced in this
paper embeds the classical pole-placement state feedback design into
a quadratic optimisation based model-predictive formulation. This
provides an alternative to model-predictive controllers which are
based on linear-quadratic control. The theoretical properties of
the controller in a linear continuous-time setting are presented and
a number of illustrative examples are given.
These results provide the foundation for novel linear and nonlinear
constrained predictive control methods based on continuous-time
models.},
doi = {10.1016/S0005-1098(01)00231-X}
}
@article{GawSca02,
author = {Peter J Gawthrop and Serge Scavarda},
title = {Special Issue on Bond Graphs: Editorial},
journal = {Proceedings of the Institution of Mechanical Engineers
Pt. I: Journal of Systems and Control Engineering},
pages = {i--v},
year = 2002,
month = {March},
volume = 216,
number = {I1},
annote = {Special issue},
abstract = {Good quality control of dynamical systems relies
on good models of the controlled system; it follows that the control
engineer must also be a good system modeller and have effective
paradigms for supporting system modelling. Much control engineering
is based on the block diagram paradigm. It will be argued in
this Editorial that such use of the block diagram paradigm is
unfortunate and that the bond graph paradigm is preferable for
a number of reasons.},
pdf = {../../Publications/csc2002/GawSca02.pdf},
url = {http://dx.doi.org/10.1243/0959651021541363}
}
@article{GawWan02a,
author = {P J Gawthrop and L Wang},
title = {Transfer function and frequency response estimation using resonant filters},
journal = {Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering},
volume = 216,
number = 6,
pages = {441-453},
year = 2002,
doi = {10.1177/095965180221600601},
abstract = {A resonant filter approach is proposed for direct identification of continuous-time transfer functions from input-output data when the input contains significant periodic components. The asymptotic properties of the method are analysed; in particular, the noise reduction properties are emphasized. A simulation example is given to demonstrate the properties of the algorithm. By using a set of experimental data collected from a food cooking extruder, the proposed method has been compared with a well-known frequency response method. }
}
@article{GawPal03,
author = {P J Gawthrop and D Palmer},
title = {A Bicausal Bond Graph Representation of Operational Amplifiers},
journal = {Proceedings of the Institution of Mechanical Engineers
Pt. I: Journal of Systems and Control Engineering},
year = 2003,
volume = {217 Part I},
number = 1,
pages = {49--58},
month = {February},
abstract = {The virtual earth concept, well known to designers of active
electronic circuits with operational amplifier components, is shown
to have a novel bicausal bond graph interpretation. This leads to
simplified bond graph modelling of such circuits. Some simple
operational amplifier circuits, together with a more complex active
filter are used to illustrate the approach.
A complex electro-mechanical system shows that the method is useful
in creating a unified bond graph model of systems involving both
analogue electronic and mechanical systems.},
pdf = {../../Publications/csc2003/GawPal03.pdf},
url = {http://dx.doi.org/10.1243/095965103321196686}
}
@article{CheBalGaw03,
author = {Wen-Hua Chen and Donald J. Ballance and Peter J Gawthrop},
title = {Optimal control of nonlinear systems: a predictive control approach},
journal = {Automatica},
year = 2003,
volume = 39,
number = 4,
pages = {633-641},
month = {April},
abstract = {
A new nonlinear predictive control law for a class of multivariable
nonlinear systems is presented in this paper. It is shown that the
closed-loop dynamics under this nonlinear predictive controller
explicitly depend on design parameters (prediction time and control
order). The main features of this result are that an explicitly
analytical form of the optimal predictive controller is given, on-line
optimisation is not required, stability of the closed-loop system is
guaranteed, the whole design procedure is transparent to designers and
the resultant controller is easy to implement. By establishing the
relationship between the design parameters and time-domain transient,
it is shown that the design of an optimal generalised predictive
controller to achieve desired time-domain specifications for nonlinear
systems can be performed by looking up tables. The design procedure is
illustrated by designing an autopilot for a missile.},
pdf = {../../Publications/csc2003/CheBalGaw03.pdf},
url = {http://dx.doi.org/10.1016/S0005-1098(02)00272-8}
}
@article{WanGawChe04,
class = {Identification},
author = {Liuping Wang and Peter Gawthrop and Charlie Chessari and Tony Podsiadly and Angus Giles},
title = {Indirect approach to continuous time system identification of food extruder},
journal = {Journal of Process Control},
year = 2004,
volume = 14,
number = 6,
pages = {603-615},
month = {September},
abstract = {A three-stage approach to system identification in the
continuous time is presented which is appropriate for
day-to-day application by plant engineers in the process
industry. The three stages are: data acquisition using
relay feedback; non-parametric identification of the
system step response; and parametric model fitting of
the identified step response. The method is evaluated on
a pilot-scale food-cooking extruder.},
pdf = {../../Publications/csc2004/WanGawChe04.pdf},
doi = {10.1016/j.jprocont.2004.01.004}
}
@article{Gaw04,
class = {Bond-graph},
author = {Peter J Gawthrop},
title = {Bond Graph Based Control Using Virtual Actuators},
journal = {Proceedings of the Institution of Mechanical Engineers
Pt. I: Journal of Systems and Control Engineering},
month = {September},
year = 2004,
volume = 218,
number = 4,
pages = {251--268},
abstract = { A bond-graph based approach to design in the physical
domain is described which uses the concept of virtual actuators
and virtual sensors.
The approach is illustrated by, and implemented on, an
experimental ball and beam system},
pdf = {../../Publications/csc2004/Gaw04.pdf},
doi = {10.1243/0959651041165864}
}
@article{GawMcG04,
class = {Lego},
author = {Gawthrop, P.J. and McGookin, E.},
title = {A LEGO-based control experiment},
journal = {IEEE Control Systems Magazine},
year = 2004,
volume = 24,
number = 5,
pages = {43-56},
month = {October},
pdf = {../../Publications/csc2004/GawMcG04.pdf},
abstract = {A nice feature of the LEGO system is that, although the mechanical,
electrical, and structural construction is good enough for successful
results, there are enough discrepancies between theory and practice to
introduce the student to real-world problems of controller. This
article concentrates on implementing the feedback controller within
the RCX, with the host computer used for compiling, downloading, and
data display. However, an interesting research project is to implement
part of the controller on the host computer and communicate by means
of the IR channel. The bandwidth restriction that this approach
imposes can provide the basis for a research project on control
through a restricted bandwidth channel.
},
doi = {10.1109/MCS.2004.1337857}
}
@article{GawWalWag05,
author = {P.J. Gawthrop and M.I. Wallace and D.J. Wagg},
title = {Bond-graph Based Substructuring of Dynamical Systems},
journal = {Earthquake Engng Struc. Dyn.},
year = 2005,
volume = 34,
number = 6,
pages = {687-703},
month = {May},
abstract = {
A bond graph approach to hybrid simulation of dynamical systems using
numerical-experimental real-time substructuring is presented. The
bond graph concepts of a {virtual junction} and a {virtual
actuator}, hitherto used in the context of physical-model based
control, are used to perform the substructuring in an intuitively
appealing way. The approach is illustrated by the reworking of a
previously-published example.
The approach is verified experimentally using a bench-top multiple
mass-spring system for the physical substructure and automatically
generated real-time code is used to implement the numerical
substructure.
},
doi = {10.1002/eqe.450}
}
@article{GawWan05,
author = {P.J. Gawthrop and L. Wang},
title = {Data Compression for Estimation of the Physical Parameters
of Stable and Unstable Linear Systems},
journal = {Automatica},
year = 2005,
volume = 41,
number = 8,
pages = {1313-1321},
month = {August},
abstract = {
A two-stage method for the identification of physical system
parameters from experimental data is presented. The first stage
compresses the data as an empirical model which encapsulates
the data content at frequencies of interest. The second stage then
uses data extracted from the empirical model of the first stage
within a non-linear estimation scheme to estimate the unknown
physical parameters. Furthermore, the paper proposes use of
exponential data weighting in the identification of partially
unknown, unstable systems so that they can be treated in the same
framework of a stable system. Experimental data are used to
demonstrate the efficacy of the proposed approach.
},
doi = {10.1016/j.automatica.2005.03.013}
}
@article{Gaw05,
author = {Peter J Gawthrop},
title = {Virtual Actuators with Virtual Sensors},
journal = {Proceedings of the Institution of Mechanical Engineers
Pt. I: Journal of Systems and Control Engineering},
year = 2005,
volume = 219,
number = 5,
pages = {371 -- 377},
month = {August},
abstract = {The virtual actuator approach to bond graph based
control is extended to use virtual sensor
inputs. This allows relative degree conditions on the
controller to be relaxed. Furthermore, the effect of
the transfer system can be eliminated from the closed
loop system. Illustrative examples are given.},
doi = {10.1243/095965105X33473}
}
@article{GawWan06,
author = {Peter J. Gawthrop and Liuping Wang},
title = {Intermittent predictive control of an inverted pendulum},
journal = {Control Engineering Practice},
year = 2006,
volume = 14,
number = 11,
pages = {1347-1356},
month = {November},
doi = {10.1016/j.conengprac.2005.09.002},
abstract = {Intermittent predictive pole-placement control is successfully applied
to the constrained-state control of a prestabilised experimental inverted pendulum.}
}
@article{CheGaw06,
author = {Wen-Hua Chen and Peter J. Gawthrop},
title = {Constrained predictive pole-placement control with linear models},
journal = {Automatica},
year = 2006,
volume = {42},
number = {4},
pages = {613-618},
month = {April},
doi = {10.1016/j.automatica.2005.09.020},
abstract = {Predictive pole-placement (PPP) control is a
continuous-time MPC using a particular set of basis functions
leading to pole-placement behaviour in the unconstrained case. This
paper presents two modified versions of the PPP controller which are
each shown to have desirable stability properties when controlling
systems with input, output and state constraints.}
}
@article{VinBalGaw06,
author = {D. Vink and D. Ballance and P. Gawthrop},
title = {Bond graphs in model matching control},
journal = {Mathematical and Computer Modelling of Dynamical Systems},
year = 2006,
volume = 12,
number = {2-3},
pages = {249 - 261},
doi = {10.1080/13873950500068278},
abstract = {
Bond graphs are primarily used in the network modeling of lumped
parameter physical systems, but controller design with this graphical
technique is relatively unexplored. It is shown that bond graphs can
be used as a tool for certain model matching control designs. Some
basic facts on the nonlinear model matching problem are recalled. The
model matching problem is then associated with a particular
disturbance decoupling problem, and it is demonstrated that bicausal
assignment methods for bond graphs can be applied to solve the
disturbance decoupling problem as to meet the model matching
objective. The adopted bond graph approach is presented through a
detailed example, which shows that the obtained controller induces
port-Hamiltonian error dynamics. As a result, the closed loop system
has an associated standard bond graph representation, thereby
rendering energy shaping and damping injection possible from within a
graphical context.
}
}
@article{GawWalNeiWag06,
author = {P.J. Gawthrop and M.I. Wallace and S.A. Neild and D.J. Wagg},
title = {Robust real-time substructuring techniques for under-damped systems},
journal = {Structural Control and Health Monitoring},
volume = {14},
number = {4},
pages = {591-608},
month = {June},
year = 2007,
abstract = {This paper considers the hybrid simulation of
under-damped dynamical systems using numerical-experimental
real-time substructuring. Substructuring joins together a physical
plant with a numerical model using real-time control techniques,
such that the combined model emulates the behaviour of the entire
system. Due to the low damping, the control of substructured systems
can be highly sensitive to delay and uncertainty. We present a
technique for calculating the critical delay of the substructured
system using a phase margin approach. In addition, it is shown that
robustness techniques, drawn from feedback control theory, can be
used to reduce the destabilising effect of uncertainty. To
demonstrate this, a comparison of three different robustness
compensators is presented, using a well-known linear system. The
level of uncertainty is deliberately increased to compare their
performances and a discussion is made on when each may be most
useful.},
doi = {10.1002/stc.174},
note = {Published on-line: 19 May 2006}
}
@article{LorGawLak06,
author = {Loram, Ian David and Gawthrop, Peter and Lakie, Martin},
title = {{The frequency of human, manual adjustments in balancing an inverted pendulum is constrained by intrinsic physiological factors}},
journal = {J Physiol (Lond)},
volume = 577,
number = 1,
pages = {403-416},
doi = {10.1113/jphysiol.2006.118786},
year = 2006,
abstract = {
While standing naturally and when manually or pedally balancing an
equivalent inverted pendulum, the load sways slowly (characteristic
unidirectional duration ~1s) and the controller, calf muscles or hand,
makes more frequent adjustments (characteristic unidirectional
duration 400ms). Here we test the hypothesis that these durations
reflect load properties rather than some intrinsic property of the
human neuromuscular system. Using a specialised setup mechanically
analogous to real standing, subjects manually balanced inverted
pendulums with different moments of inertia through a compliant spring
representing the Achilles tendon. The spring bias was controlled by a
sensitive joystick via a servo motor and accurate visual feedback was
provided on an oscilloscope. As moment of inertia decreased inverted
pendulum sway size increased and it became difficult to sustain
successful balance. The mean duration of unidirectional balance
adjustments did not change. Moreover, the mean duration of
unidirectional inverted pendulum sway reduced only slightly remaining
around 1 s. The simplest explanation is that balance was maintained by
a process of manual adjustments intrinsically limited to a mean
frequency of 2 to 3 unidirectional adjustments per second
corresponding to intermittent control observed in manual tracking
experiments. Consequently the inverted pendulum sway duration,
mechanically related to the bias duration, reflects an intrinsic
constraint of the neuromuscular control system. Given the similar
durations of sway and muscle adjustments observed in real standing, we
postulate that the characteristic duration of unidirectional standing
sway reflects intrinsic intermittent control rather than the inertial
properties of the body.
},
note = {Published on-line: September 14, 2006.}
}
@article{GawBev07,
author = {Peter J Gawthrop and Geraint P Bevan},
title = {Bond-Graph Modeling: A tutorial introduction for control engineers},
journal = {IEEE Control Systems Magazine},
year = 2007,
volume = 27,
number = 2,
pages = {24--45},
month = {April},
doi = {10.1109/MCS.2007.338279}
}
@article{GawWan07,
author = {Peter J Gawthrop and Liuping Wang},
title = {Intermittent Model Predictive Control},
journal = {Proceedings of the Institution of Mechanical Engineers
Pt. I: Journal of Systems and Control Engineering},
year = 2007,
volume = 221,
number = 7,
pages = {1007-1018},
doi = {10.1243/09596518JSCE417},
abstract = {Intermittent control, where a sequence of open-loop
trajectories are punctuated by intermittent feedback, is described
and a number of design methods presented. A generalised hold
representation is derived and shown to be useful for both
implementation and analysis. The relationship between predictive
control of a time delay system and intermittent control is examined
and it is shown that a simplified predictor can be used in the
latter case.
The applicability of intermittent control to the implementation of
MPC is discussed and illustrated by the control of a difficult
mechanical system -- a self-balancing seesaw.
}
}
@article{GawWanYou07,
author = {Peter J. Gawthrop and Liuping Wang and Peter C. Young},
title = {Continuous-time non-minimal state-space design},
journal = {Int. J. Control},
year = 2007,
volume = 80,
number = 10,
pages = {690 - 1697},
note = {Published on-line: 26 July 2007},
doi = {10.1080/00207170701546006},
abstract = {
A continuous time non-minimal state-space (NMSS) representation is
shown to be explicitly related to the underlying minimal state-space
observer/state feedback design method and, moreover, the corresponding
state feedback gains are explicitly related. This result provides a
starting point for NMSS methods in the continuous-time
domain. Numerical examples are given which illustrate the underlying
relationship.}
}
@article{GawWagNei07,
author = {P.J. Gawthrop and D.J. Wagg and S.A. Neild},
title = {Bond Graph Based Control and Substructuring},
journal = {Simulation Modelling Practice and Theory},
year = 2009,
volume = {17},
number = {1},
pages = {211-227},
month = {January},
note = {Available online 19 November 2007},
doi = {10.1016/j.simpat.2007.10.005},
abstract = {A bond graph framework giving a unified treatment of both physical
model based control and hybrid experimental-numerical simulation
(also known as real-time dynamic substructuring) is presented. The
framework consists of two subsystems, one physical and one
numerical, connected by a mph{transfer system} representing
non-ideal actuators and sensors. Within this context, a two-stage
design procedure is proposed: firstly, design and/or analysis of the
numerical and physical subsystem interconnection as if the transfer
system were not present; and secondly removal of as much as possible
of the transfer system dynamics while having regard for the
stability margins established in the first stage. The approach
allows the use of engineering insight backed up by well-established
control theory; a number of possibilities for each stage are given.
The approach is illustrated using two laboratory systems: an
experimental mass-spring-damper substructured system and swing up
and hold control of an inverted pendulum. Experimental results are
provided in the latter case.
}
}
@article{GawVirNeiWag07,
author = {Gawthrop, P. J.
and Virden, D. W.
and Neild, S. A.
and Wagg, D. J.},
title = {Emulator-based control for actuator-based hardware-in-the-loop testing},
year = {2008},
journal = {Control Engineering Practice},
volume = 16,
number = 8,
pages = {897-908},
keyword = {Hardware-in-the-loop},
keyword = {Feedback control},
keyword = {Robustness},
keyword = {Automotive engineering},
doi = {10.1016/j.conengprac.2007.10.009},
note = {Available online 3 December 2007},
abstract = {Hardware-in-the-loop (HWiL) is a form of component testing where hardware components are linked with software models. In order to test mechanical components an additional transfer system is required to link the software and hardware subsystems. The transfer system typically comprises sensors and actuators and the dynamic effects of these components need to be eliminated to give accurate results. In this paper an emulator-based control strategy is presented for actuator-based HWiL. Emulator-based control can solve the twin problems of stability and fidelity caused by the unwanted transfer system (actuator) dynamics. Significantly EBC can emulate the inverse of a transfer system which is not causally invertible, allowing a wider range of more complex transfer systems to be controlled. A robustness analysis is given and experimental results presented.}
}
@article{GawLakLor08,
author = {P.J. Gawthrop and M.D. Lakie and I.D. Loram},
title = {Predictive Feedback Control and {Fitts'} Law},
journal = {Biological Cybernetics},
year = 2008,
volume = 98,
number = 3,
pages = {229-238},
month = {March},
note = {Published online: 5 January 2008},
doi = {10.1007/s00422-007-0206-9},
abstract = {
Fitts' law is a well established empirical formula, known for
encapsulating the ``speed-accuracy trade-off''. For discrete, manual
movements from a starting location to a target, Fitts' law relates
movement duration to the distance moved and target size. The
widespread empirical success of the formula is suggestive of
underlying principles of human movement control. There have been
previous attempts to relate Fitts' law to engineering-type control
hypotheses and it has been shown that the law is exactly consistent
with the closed-loop step-response of a time-delayed, first-order
system. Assuming only the operation of closed-loop feedback, either
continuous or intermittent, this paper asks whether such feedback
should be predictive or not predictive to be consistent with Fitts
law. Since Fitts' law is equivalent to a time delay separated from a
first-order system, known control theory implies that the controller
must be predictive. A predictive controller moves the time-delay
outside the feedback loop such that the closed- loop response can be
separated into a time delay and rational function whereas a non-
predictive controller retains a state delay within feedback loop
which is not consistent with Fitts' law. Using sufficient
parameters, a high-order non-predictive controller could
approximately reproduce Fitts' law. However, such high-order,
``non-parametric'' controllers are essentially empirical in nature,
without physical meaning, and therefore are conceptually inferior to
the predictive controller. It is a new insight that using
closed-loop feedback, prediction is required to physically explain
Fitts' law. The implication is that prediction is an inherent part of
the ``speed-accuracy trade-off''.
}
}
@article{GawNeiGonWag08,
author = {P.J. Gawthrop and S.A. Neild and A. Gonzalez-Buelga and D.J. Wagg},
title = {Causality in real-time dynamic substructure testing},
journal = {Mechatronics},
year = 2010,
volume = 19,
number = 7,
pages = {1105--1115},
month = {October},
note = {Available online 16 April 2008},
abstract = { Causality, in the bond graph sense, is shown to provide
a conceptual framework for the design of real-time
dynamic substructure testing experiments. In
particular, known stability problems with
split-inertia substructured systems are
reinterpreted as causality issues within the new
conceptual framework. As an example, causality
analysis is used to provide a practical solution to
a split-inertia substructuring problem and the
solution is experimentally verified.},
doi = {10.1016/j.mechatronics.2008.02.005}
}
@article{GawWan09,
author = {Gawthrop, Peter J.
and Wang, Liuping},
title = {Constrained intermittent model predictive control},
journal = {International Journal of Control},
year = 2009,
publisher = {Taylor and Francis},
volume = 82,
issue = 6,
pages = {1138--1147},
abstract = {The generalised hold formulation of intermittent control is re-examined and shown to have some useful theoretical and practical properties. It is shown that this provides a foundation for constrained model predictive control in an intermittent context. The method is illustrated using an example and verified with experimental results.},
issn = {0020-7179},
note = {Published online 27 January 2009},
doi = {10.1080/00207170802474702}
}
@article{LorLakGaw09,
author = {Loram, Ian D. and Lakie, Martin and Gawthrop, Peter J.},
title = {{Visual control of stable and unstable loads: what is the feedback delay and extent of linear time-invariant control?}},
journal = {J Physiol},
volume = 587,
number = 6,
pages = {1343-1365},
doi = {10.1113/jphysiol.2008.166173},
year = 2009,
abstract = {Human balance is commonly described using linear-time-invariant (LTI) models. The feedback time delay determines the position of balance in the motor-control hierarchy. The extent of LTI control illuminates the automaticity of the control process. Using non-parametric analysis, we measured the feedback delay, extent of LTI control and visuo-motor transfer function in six randomly disturbed, visuo-manual compensatory tracking tasks analogous to standing with small mechanical perturbations and purely visual information. The delay depended primarily on load order (2nd: 220 {+/-} 30 ms, 1st: 124 {+/-} 20 ms), and secondarily on visual magnification (extent 2nd: 34 ms, 1st: 8 ms) and was unaffected by load stability. LTI control explained 1st order and stable loads relatively well. For unstable (85 passive stabilisation) 2nd order loads, LTI control accounted for 40 of manual output at 0.1 Hz decreasing below 10 as frequency increased through the important 1-3 Hz region where manual power and visuo-motor gain are high. Visual control of unstable 2nd order loads incurs substantial feedback delays and the control process will not be LTI. These features do not result from exclusive use of visual inputs because we found much shorter delays and a greater degree of LTI control when subjects visually controlled a 1st order load. Rather, these results suggest that delay and variability are inevitable when more flexible, intentional mechanisms are required to control 2nd order unstable loads. The high variability of quiet standing, and movement generally, may be indicative of flexible, variable delay, intentional mechanisms rather than the automatic LTI responses usually reported in response to large perturbations.
}
}
@article{WanYouGawTay09,
author = {Wang, Liuping
and Young, Peter C.
and Gawthrop, Peter J.
and Taylor, C. James},
title = {Non-minimal state-space model-based continuous-time model predictive control with constraints},
journal = {International Journal of Control},
year = 2009,
volume = 82,
issue = 6,
pages = {1122--1137},
publisher = {Taylor and Francis},
abstract = {This article proposes a model predictive control scheme based on a non-minimal state-space (NMSS) structure. Such a combination yields a continuous-time state-space model predictive control system that permits hard constraints to be imposed on both plant input and output variables, whilst using NMSS output-feedback without the need for an observer. A comparison between the NMSS and observer-based approaches using Monte Carlo uncertainty analysis shows that the former design is considerably less sensitive to plant-model mismatch than the latter. Through simulation studies, the article also investigates the role of the implementation filter in noise attenuation, disturbance rejection and robustness of the closed-loop predictive control system. The results show that the filter poles become a subset of the closed-loop poles and this provides a straightforward method of tuning the closed-loop performance to achieve a reasonable balance between speed of response, disturbance rejection, measurement noise attenuation and robustness.},
issn = {0020-7179},
doi = {10.1080/00207170802474694},
note = {Published online 16 March 2009}
}
@article{Gaw09,
author = {Peter J Gawthrop},
title = {Frequency Domain Analysis of Intermittent Control},
journal = {Proceedings of the Institution of Mechanical Engineers
Pt. I: Journal of Systems and Control Engineering},
year = 2009,
volume = 223,
number = 5,
pages = {591-603},
doi = {10.1243/09596518JSCE759},
abstract = {
Intermittent control is a feedback control design method that
combines both continuous-time and discrete-time domains; a recent
result shows that this form of intermittent control can be
rewritten as a sampled-data feedback system with a particular
vector generalised hold. This paper builds on this result to give,
for the first time, a frequency domain analysis of the closed-loop
system containing an intermittent controller.
This analysis is illustrated using two examples. The first example
is related to the human balance control system and us thus
physiologically relevant. The second example gives a theoretical
explanation of the phenomenon of self-induced oscillations in
intermittent control systems.
}
}
@article{GawWan09a,
author = {Peter J Gawthrop and Liuping Wang},
title = {Event-driven Intermittent Control},
journal = {International Journal of Control},
year = 2009,
note = {Published online 09 July 2009},
volume = 82,
number = 12,
pages = {2235 - 2248},
month = {December},
doi = {10.1080/00207170902978115},
abstract = {
An intermittent controller with fixed sampling interval is recast as
an event-driven controller. The key aspect of intermittent control
that makes this possible is the use of basis functions, or,
equivalently, a generalised hold, to generate the intersample
open-loop control signal. The controller incorporates both
feedforward events in response to known signals and feedback events
in response to detected disturbances. The latter feature makes use
of an extended basis-function generator to generate open-loop
predictions of states to be compared with measured or observed
states. Intermittent control is based on an underlying
continuous-time controller; it is emphasised that the design of this
continuous-time controller is important, particularly in the
presence of input disturbances. Illustrative simulation examples
are given.
}
}
@article{GawLorLak09,
author = {Peter Gawthrop and Ian Loram and Martin Lakie},
title = {Predictive Feedback in Human Simulated Pendulum Balancing},
journal = {Biological Cybernetics},
year = 2009,
volume = 101,
number = 2,
pages = {131-146},
doi = {10.1007/s00422-009-0325-6},
note = {Published online July 09, 2009},
abstract = {
In studies of human balance, it is common to fit stimulus-response
data by tuning the time-delay and gain parameters of a simple
delayed feedback model. Many interpret this fitted model, a simple
delayed feedback model, as evidence that predictive processes are
not required to explain existing data on standing balance.
However, two questions lead us to doubt this approach. First, does
fitting a delayed feedback model lead to reliable estimates of the
time-delay? Second, can a non-predictive controller provide an
explanation compatible with the independently estimated time delay?
For methodological and experimental clarity, we study human
balancing of a simulated inverted pendulum via joystick and
screen. A two-step approach to data analysis is used: firstly a
non-parametric model - the closed-loop impulse response - is
estimated from the experimental data; secondly, a parametric model
is fitted to the non-parametric impulse-response by adjusting
time-delay and controller parameters. To support the second step, a
new explicit formula relating controller parameters to closed-loop
impulse response is derived. Two classes of controller are
investigated within a common state-space context: non-predictive and
predictive.
It is found that the time-delay estimate arising from the second
step is strongly dependent on which controller class is assumed; in
particular, the non-predictive control assumption leads to
time-delay estimates that are smaller than those arising from the
predictive assumption.
Moreover, the time-delays estimated using the non-predictive control
assumption are not consistent with a lower-bound on the time-delay
of the non-parametric model whereas the corresponding predictive
result is consistent. Thus while the goodness of fit only marginally
favoured predictive over non-predictive control, if we add the
additional constraint that the model must reproduce the
non-parametric time delay, then the non-predictive control model
fails. We conclude (i) the time-delay should be estimated
independently of fitting a low order parametric model, (ii) that
balance of the simulated inverted pendulum could not be explained by
the non-predictive control model and (iii) that predictive control
provided a better explanation than non-predictive control.
}
}
@article{GawBhiMoh09,
title = {Physical-model-based control of a piezoelectric tube for nano-scale positioning applications},
journal = {Mechatronics},
volume = 20,
number = 1,
pages = {74 - 84},
month = {February},
year = 2010,
issn = {0957-4158},
doi = {10.1016/j.mechatronics.2009.09.006},
author = {P.J. Gawthrop and B. Bhikkaji and S.O.R. Moheimani},
keywords = {Flexible structures},
keywords = {Piezoelectric transducers},
keywords = {Charge control},
keywords = {Vibration control},
keywords = {Bond graphs},
keywords = {Physical-model-based control},
abstract = {
Piezoelectric tubes exhibit a highly resonant mode of vibration which, if uncontrolled, limits the maximum scan rate in nano-scale positioning applications. Highly resonant systems with collocated sensor/actuator are often controlled using resonant shunt dampers. Unfortunately, in the configuration used here, this approach is not possible due the non-minimum phase property arising from the presence of a right-half plane zero.
This problem is solved by: (i) interpreting the resonant shunt damper in the context of physical-model-based control (PMBC) and (ii) extending the PMBC approach to handle non-minimum phase systems.
The resultant controller combines the physical insight of the resonant shunt damper with the ability to control the non-minimum phase piezoelectric tube.
A digital implementation of the controller was experimentally evaluated and found to successfully eliminate the resonant mode of vibration during an accurate and fast scan using a piezoelectric tube actuator.},
note = {Available online 13 October 2009}
}
@article{Gaw09a,
author = {P.J. Gawthrop},
title = {Act-and-Wait and Intermittent Control: Some Comments},
journal = {IEEE Transactions on Control Systems Technology},
year = 2009,
note = {Published on-line: 10/11/2009},
doi = {10.1109/TCST.2009.2034403},
issn = {1063-6536},
abstract = {The act-and-wait control introduced by Insperger is shown to be related
to a form of intermittent control. Theoretical and practical similarities
and differences between the two methods are explored.}
}
@article{Gaw09b,
author = {Peter Gawthrop},
title = {Spherical Panoramas},
journal = {Journal of the Royal Photographic Society},
year = 2009,
volume = 149,
number = 2,
pages = {118-121},
month = {March},
url = {http://www.lightspacewater.net/Tutorials/OSP/PerspectivePanorama/Gaw09b.pdf}
}
@article{WanGawOweRog10,
author = {Wang, Liuping
and Gawthrop, Peter
and Owens, David. H.
and Rogers, Eric},
title = {Switched linear model predictive controllers for periodic exogenous signals},
journal = {International Journal of Control},
year = 2010,
publisher = {Taylor and Francis},
volume = 83,
issue = 4,
pages = {848--861},
doi = {10.1080/00207170903460501},
abstract = {This article develops switched linear controllers for periodic exogenous signals using the framework of a continuous-time model predictive control. In this framework, the control signal is generated by an algorithm that uses receding horizon control principle with an on-line optimisation scheme that permits inclusion of operational constraints. Unlike traditional repetitive controllers, applying this method in the form of switched linear controllers ensures bumpless transfer from one controller to another. Simulation studies are included to demonstrate the efficacy of the design with or without hard constraints.},
issn = {0020-7179}
}
@article{GawWan10,
author = {Gawthrop, Peter J.
and Wang, Liuping},
title = {Intermittent redesign of continuous controllers},
journal = {International Journal of Control},
year = 2010,
publisher = {Taylor and Francis},
volume = 83,
issue = 8,
pages = {1581--1594},
doi = {10.1080/00207179.2010.483691},
abstract = {The reverse-engineering idea developed by Maciejowski in the context of model-based predictive control is applied to the redesign of continuous-time compensators as intermittent controllers. Not only does this give a way of designing constrained input and state versions of continuous-time compensators but also provides a method for turning continuous-time compensators into event-driven versions. The procedure is illustrated by three examples: an event-driven PID controller relevant to the human balance control problem, a constrained version of the classical mechanical vibration absorber of den Hartog and an event driven and constrained vibration absorber.},
issn = {0020-7179}
}
@article{LorGolLakGaw10,
author = {Loram, Ian David and Gollee, Henrik and Lakie, Martin and Gawthrop, Peter},
title = {{Human control of an inverted pendulum: Is continuous control necessary? Is intermittent control effective? Is intermittent control physiological?}},
volume = 589,
issue = 2,
pages = {307-324},
doi = {10.1113/jphysiol.2010.194712},
abstract = {Human motor control is often explained in terms of engineering ″servo″ theory. Recently, continuous, optimal control using internal models has emerged as a leading paradigm for voluntary movement. However, these engineering paradigms are designed for high bandwidth, inflexible, consistent systems whereas human control is low bandwidth and flexible using noisy sensors and actuators. By contrast, engineering intermittent control was designed for bandwidth-limited applications. Our general interest is whether intermittent rather than continuous control is generic to human motor control. Currently, it would be assumed that continuous control is the superior and physiologically natural choice for controlling unstable loads, for example as required for maintaining human balance. Using visual manual tracking of an unstable load, we show that control using gentle, intermittent taps is entirely natural and effective. The gentle tapping method resulted in slightly superior position control and velocity minimisation, a reduced feedback time delay, greater robustness to changing actuator gain and equal or greater linearity with respect to the external disturbance. Control was possible with a median contact rate of 0.8±0.3 s-1. However, when optimising position or velocity regulation, a modal contact rate of 2s-1 was observed. This modal rate was consistent with insignificant disturbance-joystick coherence beyond 1-2 Hz in both tapping and continuous contact methods. For this load, these results demonstrate a motor control process of serial ballistic trajectories limited to an optimum rate of 2 s-1. Consistent with theoretical reasoning, our results suggest that intermittent open loop action is a natural consequence of human physiology.},
journal = {The Journal of Physiology},
note = {Published online November 22, 2010},
year = 2011
}
@article{GawLorLakGol11,
author = {Peter Gawthrop and Ian Loram and Martin Lakie and Henrik Gollee},
title = {Intermittent Control: A Computational Theory of Human Control},
journal = {Biological Cybernetics},
year = 2011,
volume = 104,
number = {1-2},
pages = {31-51},
doi = {10.1007/s00422-010-0416-4},
note = {Published online: 17th February 2011},
abstract = {Human motor control is often explained in terms of engineering ″servo″ theory. Recently, continuous, optimal control using internal models has emerged as a leading paradigm for voluntary movement. However, these engineering paradigms are designed for high bandwidth, inflexible, consistent systems whereas human control is low bandwidth and flexible using noisy sensors and actuators. By contrast, engineering intermittent control was designed for bandwidth-limited applications. Our general interest is whether intermittent rather than continuous control is generic to human motor control. Currently, it would be assumed that continuous control is the superior and physiologically natural choice for controlling unstable loads, for example as required for maintaining human balance. Using visual manual tracking of an unstable load, we show that control using gentle, intermittent taps is entirely natural and effective. The gentle tapping method resulted in slightly superior position control and velocity minimisation, a reduced feedback time delay, greater robustness to changing actuator gain and equal or greater linearity with respect to the external disturbance. Control was possible with a median contact rate of 0.8±0.3 s-1. However, when optimising position or velocity regulation, a modal contact rate of 2s-1 was observed. This modal rate was consistent with insignificant disturbance-joystick coherence beyond 1-2 Hz in both tapping and continuous contact methods. For this load, these results demonstrate a motor control process of serial ballistic trajectories limited to an optimum rate of 2 s-1. Consistent with theoretical reasoning, our results suggest that intermittent open loop action is a natural consequence of human physiology. }
}
@article{GawWan11,
author = {Gawthrop, Peter and Wang, Liuping},
title = {The system-matched hold and the intermittent control separation principle},
journal = {International Journal of Control},
volume = 84,
number = 12,
pages = {1965-1974},
year = 2011,
doi = {10.1080/00207179.2011.630759},
abstract = { An intermittent controller is a form of hybrid controller which adds a generalised sample and hold mechanism to an underlying continuous-time feedback control system. The sampling may be non-uniform or event driven. One particular form of the hold, termed the system-matched hold (SMH) mimics the behaviour of the closed-loop feedback control signal during the intermittent intervals. It is shown in this article that this choice of hold leads to an intermittent separation principle. In particular, this simple analytical result ensures that when using the SMH, the separation properties of the underlying state-estimate feedback control system carry over to the intermittent control system. This separation principle for the SMH has the important consequence that, unlike the zero-order hold case, the stability of the closed-loop system in the fixed sampling case is not dependent on sample interval. It is therefore suggested that the SMH should replace the conventional zero-order hold in circumstances where the sample interval is unknown, time-varying or determined by events. }
}
@article{GawNeiWag12,
author = {Gawthrop, Peter J. and Neild, Simon A. and Wagg, David J.},
title = {Semi-active damping using a hybrid control approach},
year = 2012,
doi = {10.1177/1045389X12436734},
abstract = {In this article, a hybrid control framework is used to design semi-active controllers for vibration reduction. It is shown that the semi-active skyhook damper, typically used for vibration reduction, can be recast in the framework of an event-driven intermittent controller. By doing this, we can then exploit the well-developed techniques associated with hybrid control theory to design the semi-active control system. Illustrative simulation examples are based on a 2 degree-of-freedom system, often used to model the dynamics of a quarter car body model. The simulation results demonstrate how hybrid control design techniques can improve the overall performance of the semi-active control system.},
journal = {Journal of Intelligent Material Systems and Structures},
note = {Published online February 21, 2012}
}
@article{LorKamGolGaw12,
author = {Loram, Ian D. and {van de Kamp}, Cornelis and Gollee, Henrik and Gawthrop, Peter J.},
title = {Identification of intermittent control in man and machine},
volume = {9},
number = {74},
pages = {2070-2084},
year = {2012},
doi = {10.1098/rsif.2012.0142},
abstract = {Regulation by negative feedback is fundamental to engineering and biological processes. Biological regulation is usually explained using continuous feedback models from both classical and modern control theory. An alternative control paradigm, intermittent control, has also been suggested as a model for biological control systems, particularly those involving the central nervous system. However, at present, there is no identification method explicitly formulated to distinguish intermittent from continuous control; here, we present such a method. The identification experiment uses a special paired-step set-point sequence. The corresponding data analysis use a conventional ARMA model to relate a theoretically derived equivalent set-point to control signal; the novelty lies in sequentially and iteratively adjusting the timing of the steps of this equivalent set-point to optimize the linear time-invariant fit. The method was verified using realistic simulation data and was found to robustly distinguish not only between continuous and intermittent control but also between event-driven intermittent and clock-driven intermittent control. When applied to human pursuit tracking, event-driven intermittent control was identified, with an intermittent interval of 260–310 ms (n = 6, p < 0.05). This new identification method is applicable for machine and biological applications.},
journal = {Journal of The Royal Society Interface},
note = {Published on-line April 4, 2012}
}
@article{GawGol12,
author = {Gawthrop, Peter J and Gollee, Henrik},
title = {Intermittent tapping control},
volume = 226,
number = 9,
pages = {1262-1273},
year = 2012,
doi = {10.1177/0959651812450114},
abstract = {Control using a sequence of ‘taps’, in contrast to the usual smooth control, is shown to fit within the established intermittent control framework. In particular, a specially designed generalised hold gives rise to tapping behaviour optimised according to the underlying linear-quadratic design. Both fixed-interval and event-driven tapping are included in this approach and some basic stability analysis is given. Illustrative examples are presented and the advantages of tapping in the context of electromechanical servo systems with friction are explored using a laboratory experiment.},
journal = {Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering},
note = {Published online on July 26, 2012}
}
@article{GolMamLorGaw12,
author = {H. Gollee and A. Mamma and I. D. Loram and P. J. Gawthrop},
title = {Frequency-domain Identification of the Human Controller},
year = 2012,
issn = {0340-1200},
journal = {Biological Cybernetics},
volume = 106,
issue = {6-7},
doi = {10.1007/s00422-012-0503-9},
pages = {359-372},
note = {Published online: 14 July 2012},
abstract = {
System identification techniques applied to experimental human-in-the-loop data provide an objective test of three alternative control–theoretical models of the human control system: non-predictive control, predictive control, and intermittent predictive control. A two-stage approach to the identification of a single-input single-output control system is used: first, the closed-loop frequency response is derived using the periodic property of the experimental data, followed by the fitting of a parametric model. While this approach is well-established for non-predictive and predictive control, it is here used for the first time with intermittent predictive control. This technique is applied to data from experiments with human volunteers who use one of two control strategies, focusing either on position or on velocity, to manually control a virtual, unstable load which requires sustained feedback to maintain position or low velocity. The results show firstly that the non-predictive controller does not fit the data as well as the other two models, and secondly that the predictive and intermittent predictive controllers provide equally good models which cannot be distinguished using this approach. Importantly, the second observation implies that sustained visual manual control is compatible with intermittent control, and that previous results suggesting a continuous control model for the human control system do not rule out intermittent control as an alternative hypothesis. Thirdly, the parameters identified reflect the control strategy adopted by the human controller.
}
}
@article{GawWagNeiWan12,
author = {Gawthrop, Peter and Wagg, David and Neild, Simon and Wang, Liuping},
title = {Power-constrained intermittent control},
journal = {International Journal of Control},
volume = 86,
number = 3,
pages = {396-409},
year = 2013,
doi = {10.1080/00207179.2012.733888},
abstract = { In this article, input power, as opposed to the usual input amplitude, constraints are introduced in the context of intermittent control. They are shown to result in a combination of quadratic optimisation and quadratic constraints. The main motivation for considering input power constraints is its similarity with semi-active control. Such methods are commonly used to provide damping in mechanical systems and structures. It is shown that semi-active control can be re-expressed and generalised as control with power constraints and can thus be implemented as power-constrained intermittent control. The method is illustrated using simulations of resonant mechanical systems and the constrained nature of the power flow is represented using power-phase-plane plots. We believe the approach we present will be useful for the control design of both semi-active and low-power vibration suppression systems. },
note = {Published online 30 Oct 2012}
}
@article{KamGawGolLor13,
author = {{van de Kamp}, Cornelis AND Gawthrop, Peter J.
AND Gollee, Henrik AND Loram, Ian D.},
journal = {PLoS Comput Biol},
publisher = {Public Library of Science},
title = {Refractoriness in Sustained Visuo-Manual Control: Is the Refractory Duration Intrinsic or Does It Depend on External System Properties?},
year = 2013,
month = 01,
volume = 9,
pages = {e1002843},
abstract = {In biology, the control of physiological variables such as body position, blood pressure and body temperature is founded on negative feedback mechanisms governing homeostasic input-output relations. The conceptual models capturing the underlying control principles are often drawn from engineering control theory. The visuo-manual control of external systems (like balancing a stick on the palm of one's hand) has traditionally been interpreted using continuous paradigms such as the servo controller or the continuous optimal controller. These engineering controllers were designed for machine systems with precise sensors, consistent actuators, short time delays and fast computers. Quite the opposite is true for the human movement system that is characterized by long neuromuscular delays, variability, history dependence and fatigue. Serial ballistic control offers an alternative control paradigm in which smooth control proceeds as a sequence of sub-movements each planned using current sensory information but then intermittently executed “open loop”. In the current study we are the first to formally identify refractoriness, a behavioural characteristic that discriminates intermittent (serial ballistic) from continuous control, in the domain of sustained (non-discrete) control of first and second order systems providing definite evidence for the validity of intermittent open-loop control as a paradigm for sustained human control.},
number = 1,
doi = {10.1371/journal.pcbi.1002843}
}
@article{KamGawGolLakLor13,
author = {{van de Kamp}, Cornelis and Gawthrop, Peter and Gollee, Henrik and Lakie, Martin and Loram, Ian David},
title = {Interfacing sensory input with motor output: does the control architecture converge to a serial process along a single channel?},
journal = {Frontiers in Computational Neuroscience},
volume = 7,
year = 2013,
number = 55,
doi = {10.3389/fncom.2013.00055},
issn = {1662-5188},
abstract = {Modular organisation in control architecture may underlie the versatility of human motor control; but the nature of the interface relating sensory input through task-selection in the space of performance variables to control actions in the space of the elemental variables is currently unknown. Our central question is whether the control architecture converges to a serial process along a single channel? In discrete reaction time experiments, psychologists have firmly associated a serial single channel hypothesis with refractoriness and response selection (psychological refractory period). Recently, we developed a methodology and evidence identifying refractoriness in sustained control of an external single degree-of-freedom system. We hypothesise that multi-segmental whole-body control also shows refractoriness. Eight participants controlled their whole body to ensure a head marker tracked a target as fast and accurately as possible. Analysis showed enhanced delays in response to stimuli with close temporal proximity to the preceding stimulus. Consistent with our preceding work, this evidence is incompatible with control as a linear time invariant process. This evidence is consistent with a single-channel serial ballistic process within the intermittent control paradigm with an intermittent interval of around 0.5 s. A control architecture reproducing intentional human movement control must reproduce refractoriness. Intermittent control is designed to provide computational time for an online optimisation process and is appropriate for flexible adaptive control. For human motor control we suggest that parallel sensory input converges to a serial, single channel process involving planning, selection and temporal inhibition of alternative responses prior to low dimensional motor output. Such design could aid robots to reproduce the flexibility of human control.}
}
@article{GawLeeHalODw13,
year = 2013,
issn = {0340-1200},
journal = {Biological Cybernetics},
volume = {107},
number = {6},
doi = {10.1007/s00422-013-0564-4},
title = {Human stick balancing: an intermittent control explanation},
publisher = {Springer Berlin Heidelberg},
author = {Gawthrop, Peter and Lee, Kwee-Yum and Halaki, Mark and O'Dwyer, Nicholas},
pages = {637-652},
language = {English},
note = {Published online: 13th August 2013},
abstract = { There are two issues in balancing a stick pivoting on a
finger tip (or mechanically on a moving cart):
maintaining the stick angle near to vertical and
maintaining the horizontal position within the
bounds of reach or cart track. The (linearised)
dynamics of the angle are second order (although
driven by pivot acceleration), and so, as in human
standing, control of the angle is not, by itself
very difficult. However, once the angle is under
control, the position dynamics are, in general,
fourth order. This makes control quite difficult for
humans (and even an engineering control system
requires careful design). Recently, three of the
authors have experimentally demonstrated that humans
control the stick angle in a special way: the
closed-loop inverted pendulum behaves as a
non-inverted pendulum with a virtual pivot somewhere
between the stick centre and tip and with increased
gravity. Moreover, they suggest that the virtual
pivot lies at the radius of gyration (about the mass
centre) above the mass centre. This paper gives a
continuous-time control-theoretical interpretation
of the virtual-pendulum approach. In particular, by
using a novel cascade control structure, it is shown
that the horizontal control of the virtual pivot
becomes a second-order problem which is much easier
to solve than the generic fourth-order
problem. Hence, the use of the virtual pivot
approach allows the control problem to be perceived
by the subject as two separate second-order problems
rather than a single fourth-order problem, and the
control problem is therefore simplified. The
theoretical predictions are verified using the data
previously presented by three of the authors and
analysed using a standard parameter estimation
method. The experimental data indicate that although
all subjects adopt the virtual pivot approach, the
less expert subjects exhibit larger amplitude
angular motion and poorly controlled translational
motion. It is known that human control systems are
delayed and intermittent, and therefore, the
continuous-time strategy cannot be correct. However,
the model of intermittent control used in this paper
is based on the virtual pivot continuous-time
control scheme, handles time delays and moreover
masquerades as the underlying continuous-time
controller. In addition, the event-driven properties
of intermittent control can explain experimentally
observed variability. }
}
@article{GawLorGolLak14,
year = 2014,
issn = {0340-1200},
journal = {Biological Cybernetics},
doi = {10.1007/s00422-014-0587-5},
title = {Intermittent control models of human standing: similarities and differences},
publisher = {Springer Berlin Heidelberg},
keywords = {Intermittent control; Predictive control; Human balancing; Quiet standing},
author = {Gawthrop, Peter and Loram, Ian and Gollee, Henrik and Lakie, Martin},
volume = 108,
number = 2,
pages = {159-168},
language = {English},
abstract = { Two architectures of intermittent control are compared
and contrasted in the context of the single inverted
pendulum model often used for describing standing in
humans. The architectures are similar insofar as
they use periods of open-loop control punctuated by
switching events when crossing a switching surface
to keep the system state trajectories close to
trajectories leading to equilibrium. The
architectures differ in two significant
ways. Firstly, in one case, the open-loop control
trajectory is generated by a system-matched hold,
and in the other case, the open-loop control signal
is zero. Secondly, prediction is used in one case
but not the other. The former difference is examined
in this paper. The zero control alternative leads to
periodic oscillations associated with limit cycles;
whereas the system-matched control alternative gives
trajectories (including homoclinic orbits) which
contain the equilibrium point and do not have
oscillatory behaviour. Despite this difference in
behaviour, it is further shown that behaviour can
appear similar when either the system is perturbed
by additive noise or the system-matched trajectory
generation is perturbed. The purpose of the research
is to come to a common approach for understanding
the theoretical properties of the two alternatives
with the twin aims of choosing which provides the
best explanation of current experimental data (which
may not, by itself, distinguish beween the two
alternatives) and suggesting future experiments to
distinguish beween the two alternatives. },
note = {Published online 6th {February} 2014.}
}
@article{LorKamLakGolGaw14,
author = {Loram, Ian D. and {van de Kamp}, Cornelis and Lakie, Martin
and Gollee, Henrik and Gawthrop, Peter J},
title = {Does the motor system need intermittent control?},
journal = {Exercise and Sport Sciences Reviews},
year = 2014,
month = {July},
volume = 42,
number = 3,
pages = {117-125},
doi = {10.1249/JES.0000000000000018},
note = {Published online 9 May 2014},
abstract = {Explanation of motor control is dominated by continuous neurophysiological pathways (e.g. trans-cortical, spinal) and the continuous control paradigm. Using new theoretical development, methodology and evidence, we propose intermittent control, which incorporates a serial ballistic process within the main feedback loop, provides a more general and more accurate paradigm necessary to explain attributes highly advantageous for competitive survival and performance.}
}
@article{GawCra14,
author = {Gawthrop, Peter J. and Crampin, Edmund J.},
title = {Energy-based analysis of biochemical cycles using bond graphs},
volume = 470,
number = 2171,
year = 2014,
doi = {10.1098/rspa.2014.0459},
archiveprefix = {arXiv},
eprint = {1406.2447},
abstract = {Thermodynamic aspects of chemical reactions have a long history in the physical chemistry literature. In particular, biochemical cycles require a source of energy to function. However, although fundamental, the role of chemical potential and Gibb's free energy in the analysis of biochemical systems is often overlooked leading to models which are physically impossible. The bond graph approach was developed for modelling engineering systems, where energy generation, storage and transmission are fundamental. The method focuses on how power flows between components and how energy is stored, transmitted or dissipated within components. Based on the early ideas of network thermodynamics, we have applied this approach to biochemical systems to generate models which automatically obey the laws of thermodynamics. We illustrate the method with examples of biochemical cycles. We have found that thermodynamically compliant models of simple biochemical cycles can easily be developed using this approach. In particular, both stoichiometric information and simulation models can be developed directly from the bond graph. Furthermore, model reduction and approximation while retaining structural and thermodynamic properties is facilitated. Because the bond graph approach is also modular and scaleable, we believe that it provides a secure foundation for building thermodynamically compliant models of large biochemical networks.},
journal = {Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science},
pages = {1--25},
note = {Available at {arXiv:1406.2447}}
}
@article{GawNeiWag15,
author = {Gawthrop, Peter and Neild, S.A. and Wagg, D.J.},
title = {Dynamically dual vibration absorbers: a bond graph approach to vibration control},
journal = {Systems Science and Control Engineering},
volume = 3,
number = 1,
pages = {113-128},
year = 2015,
doi = {10.1080/21642583.2014.991458},
abstract = { This paper investigates the use of an actuator and sensor pair coupled via a control system to damp out oscillations in resonant mechanical systems. Specifically the designs emulate passive control strategies, resulting in controller dynamics that resemble a physical system. Here, the use of the novel dynamically dual approach is proposed to design the vibration absorbers to be implemented as the controller dynamics; this gives rise to the dynamically dual vibration absorber (DDVA). It is shown that the method is a natural generalisation of the classical single-degree of freedom mass–spring–damper vibration absorber and also of the popular acceleration feedback controller. This generalisation is applicable to the vibration control of arbitrarily complex resonant dynamical systems. It is further shown that the DDVA approach is analogous to the hybrid numerical-experimental testing technique known as substructuring. This analogy enables methods and results, such as robustness to sensor/actuator dynamics, to be applied to dynamically dual vibration absorbers. Illustrative experiments using both a hinged rigid beam and a flexible cantilever beam are presented. }
}
@article{GawCurCra15,
author = {Gawthrop, Peter J. and Cursons, Joseph and Crampin, Edmund J.},
title = {Hierarchical bond graph modelling of biochemical networks},
volume = 471,
number = 2184,
year = 2015,
doi = {10.1098/rspa.2015.0642},
publisher = {The Royal Society},
abstract = {The bond graph approach to modelling biochemical networks is extended to allow hierarchical construction of complex models from simpler components. This is made possible by representing the simpler components as thermodynamically open systems exchanging mass and energy via ports. A key feature of this approach is that the resultant models are robustly thermodynamically compliant: the thermodynamic compliance is not dependent on precise numerical values of parameters. Moreover, the models are reusable owing to the well-defined interface provided by the energy ports. To extract bond graph model parameters from parameters found in the literature, general and compact formulae are developed to relate free-energy constants and equilibrium constants. The existence and uniqueness of solutions is considered in terms of fundamental properties of stoichiometric matrices. The approach is illustrated by building a hierarchical bond graph model of glycogenolysis in skeletal muscle.},
issn = {1364-5021},
journal = {Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences},
archiveprefix = {arXiv},
eprint = {1503.01814},
pages = {1--23},
note = {Available at {arXiv:1503.01814}}
}
@article{GawCra16,
author = {P. J. Gawthrop and E. J. Crampin},
journal = {IET Systems Biology},
title = {Modular bond-graph modelling and analysis of biomolecular systems},
year = 2016,
volume = 10,
number = 5,
pages = {187-201},
abstract = {Bond graphs can be used to build thermodynamically-compliant hierarchical models of biomolecular systems. As bond graphs have been widely used to model, analyse and synthesise engineering systems, this study suggests that they can play the same rôle in the modelling, analysis and synthesis of biomolecular systems. The particular structure of bond graphs arising from biomolecular systems is established and used to elucidate the relation between thermodynamically closed and open systems. Block diagram representations of the dynamics implied by these bond graphs are used to reveal implicit feedback structures and are linearised to allow the application of control-theoretical methods. Two concepts of modularity are examined: computational modularity where physical correctness is retained and behavioural modularity where module behaviour (such as ultrasensitivity) is retained. As well as providing computational modularity, bond graphs provide a natural formulation of behavioural modularity and reveal the sources of retroactivity. A bond graph approach to reducing retroactivity, and thus inter-module interaction, is shown to require a power supply such as that provided by the ATP ⇌ ADP + Pi reaction. The mitogen-activated protein kinase cascade (Raf-MEK-ERK pathway) is used as an illustrative example.},
keywords = {biology computing;bond graphs;enzymes;hierarchical systems;molecular biophysics;physiological models;thermodynamics;ATP⇌ADP + Pi reaction;Michaelis-Menten kinetics;Raf-MEK-ERK pathway;behavioural modularity;biomolecular systems;block diagram representations;computational modularity;intermodule interaction;mitogen-activated protein kinase cascade;modular bond-graph modelling;retroactivity;signalling networks;thermodynamically-compliant hierarchical models},
doi = {10.1049/iet-syb.2015.0083},
issn = {1751-8849},
month = {October},
publisher = {Institution of Engineering and Technology},
archiveprefix = {arXiv},
eprint = {1511.06482},
note = {Available at {arXiv:1511.06482}}
}
@article{Gaw17a,
author = {P. J. Gawthrop},
journal = {IEEE Transactions on NanoBioscience},
title = {Bond Graph Modeling of Chemiosmotic Biomolecular Energy Transduction},
year = 2017,
volume = 16,
number = 3,
pages = {177-188},
abstract = { Engineering systems modeling and analysis based on the bond
graph approach has been applied to biomolecular
systems. In this context, the notion of a
Faraday-equivalent chemical potential is introduced
which allows chemical potential to be expressed in
an analogous manner to electrical volts thus
allowing engineering intuition to be applied to
biomolecular systems. Redox reactions, and their
representation by half-reactions, are key components
of biological systems which involve both electrical
and chemical domains. A bond graph interpretation of
redox reactions is given which combines bond graphs
with the Faraday-equivalent chemical potential. This
approach is particularly relevant when the
biomolecular system implements chemoelectrical
transduction – for example chemiosmosis within the
key metabolic pathway of mitochondria: oxidative
phosphorylation. An alternative way of implementing
computational modularity using bond graphs is
introduced and used to give a physically based model
of the mitochondrial electron transport chain To
illustrate the overall approach, this model is
analyzed using the Faraday-equivalent chemical
potential approach and engineering intuition is used
to guide affinity equalisation: a energy based
analysis of the mitochondrial electron transport
chain. },
keywords = {Analytical models;Biological system modeling;Chemicals;Computational modeling;Context;Electric potential;Protons;Biological system modeling;computational systems biology;systems biology},
doi = {10.1109/TNB.2017.2674683},
issn = {1536-1241},
month = {April},
archiveprefix = {arXiv},
eprint = {1611.04264},
note = {Available at {arXiv:1611.04264}}
}
@article{GawCra17,
author = {Gawthrop, Peter J. and Crampin, Edmund J.},
title = {Energy-based analysis of biomolecular pathways},
volume = 473,
number = 2202,
year = 2017,
doi = {10.1098/rspa.2016.0825},
publisher = {The Royal Society},
archiveprefix = {arXiv},
eprint = {1611.02332},
note = {Available at {arXiv:1611.02332}},
abstract = {Decomposition of biomolecular reaction networks into pathways is a powerful approach to the analysis of metabolic and signalling networks. Current approaches based on analysis of the stoichiometric matrix reveal information about steady-state mass flows (reaction rates) through the network. In this work, we show how pathway analysis of biomolecular networks can be extended using an energy-based approach to provide information about energy flows through the network. This energy-based approach is developed using the engineering-inspired bond graph methodology to represent biomolecular reaction networks. The approach is introduced using glycolysis as an exemplar; and is then applied to analyse the efficiency of free energy transduction in a biomolecular cycle model of a transporter protein [sodium-glucose transport protein 1 (SGLT1)]. The overall aim of our work is to present a framework for modelling and analysis of biomolecular reactions and processes which considers energy flows and losses as well as mass transport.},
issn = {1364-5021},
journal = {Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences}
}
@article{GawSieKam17,
author = {P. J. Gawthrop and I. Siekmann and T. Kameneva and S. Saha and M. R. Ibbotson and E. J. Crampin},
journal = {IET Systems Biology},
title = {Bond graph modelling of chemoelectrical energy transduction},
year = 2017,
volume = 11,
number = 5,
pages = {127-138},
abstract = {Energy-based bond graph modelling of biomolecular systems is extended to include chemoelectrical transduction thus enabling integrated thermodynamically compliant modelling of chemoelectrical systems in general and excitable membranes in particular. Our general approach is illustrated by recreating a well-known model of an excitable membrane. This model is used to investigate the energy consumed during a membrane action potential thus contributing to the current debate on the trade-off between the speed of an action potential event and energy consumption. The influx of Na+ is often taken as a proxy for energy consumption; in contrast, this study presents an energy-based model of action potentials. As the energy-based approach avoids the assumptions underlying the proxy approach it can be directly used to compute energy consumption in both healthy and diseased neurons. These results are illustrated by comparing the energy consumption of healthy and degenerative retinal ganglion cells using both simulated and in vitro data.},
keywords = {biochemistry;bioelectric potentials;biomembrane transport;eye;molecular biophysics;neurophysiology;sodium;Na;biomolecular systems;chemoelectrical energy transduction;chemoelectrical systems;degenerative retinal ganglion cells;diseased neurons;energy consumption;energy-based bond graph modelling;excitable membranes;healthy neurons;healthy retinal ganglion cells;integrated thermodynamically compliant modelling;membrane action potential},
doi = {10.1049/iet-syb.2017.0006},
issn = {1751-8849},
archiveprefix = {arXiv},
eprint = {1512.00956},
note = {Available at {arXiv:1512.00956}}
}
@article{GolGawLakLor17,
author = {Gollee, Henrik and Gawthrop, Peter J. and Lakie, Martin and Loram, Ian D.},
title = {Visuo-manual tracking: does intermittent control with aperiodic sampling explain linear power and non-linear remnant without sensorimotor noise?},
journal = {The Journal of Physiology},
volume = 595,
number = 21,
issn = {1469-7793},
doi = {10.1113/JP274288},
pages = {6751--6770},
keywords = {motor control, intermittent control, variability},
year = 2017,
abstract = {
The human operator is described adequately by linear translation of sensory input to motor output. Motor output also always includes a non-linear remnant resulting from random sensorimotor noise from multiple sources, and non-linear input transformations, for example thresholds or refractory periods. Recent evidence showed that manual tracking incurs substantial, serial, refractoriness (insensitivity to sensory information of 350 and 550 ms for 1st and 2nd order systems respectively). Our two questions are: (i) What are the comparative merits of explaining the non-linear remnant using noise or non-linear transformations? (ii) Can non-linear transformations represent serial motor decision making within the sensorimotor feedback loop intrinsic to tracking? Twelve participants (instructed to act in three prescribed ways) manually controlled two systems (1st and 2nd order) subject to a periodic multi-sine disturbance. Joystick power was analysed using three models, continuous-linear-control (CC), continuous-linear-control with calculated noise spectrum (CCN), and intermittent control with aperiodic sampling triggered by prediction error thresholds (IC). Unlike the linear mechanism, the intermittent control mechanism explained the majority of total power (linear and remnant) (77–87 vs. 8–48, IC vs. CC). Between conditions, IC used thresholds and distributions of open loop intervals consistent with, respectively, instructions and previous measured, model independent values; whereas CCN required changes in noise spectrum deviating from broadband, signal dependent noise. We conclude that manual tracking uses open loop predictive control with aperiodic sampling. Because aperiodic sampling is inherent to serial decision making within previously identified, specific frontal, striatal and parietal networks we suggest that these structures are intimately involved in visuo-manual tracking.
}
}
@article{Gaw17cX,
author = {{Gawthrop}, P.~J.},
title = {{Sensitivity Properties of Intermittent Control}},
journal = {ArXiv e-prints},
archiveprefix = {arXiv},
eprint = {1705.08228},
keywords = {Computer Science - Systems and Control, Quantitative Biology - Quantitative Methods},
year = 2017,
month = may,
note = {Available at {arXiv:1705.08228}}
}
@article{Gaw18,
author = {P. Gawthrop},
journal = {IEEE Transactions on NanoBioscience},
title = {Computing Biomolecular System Steady-States},
year = 2018,
volume = 17,
number = 1,
pages = {36-43},
abstract = {A new approach to compute the equilibria and the steady-states of biomolecular systems modeled by bond graphs is presented. The approach is illustrated using a model of a biomolecular cycle representing a membrane transporter and a model of the mitochondrial electron transport chain.},
keywords = {Biological system modeling;Chemicals;Electric potential;Kinetic theory;Mathematical model;Nanobioscience;Steady-state;Biological system modeling;computational systems biology;systems biology},
doi = {10.1109/TNB.2017.2787486},
issn = {1536-1241},
month = {March},
note = {Published online 25th December 2017}
}
@article{PanGawTra18,
author = {Pan, Michael and Gawthrop, Peter J. and Tran, Kenneth and Cursons, Joseph and Crampin, Edmund J.},
title = {Bond graph modelling of the~cardiac action potential: implications for drift and non-unique steady states},
volume = 474,
number = 2214,
year = 2018,
doi = {10.1098/rspa.2018.0106},
publisher = {The Royal Society},
abstract = {Mathematical models of cardiac action potentials have become increasingly important in the study of heart disease and pharmacology, but concerns linger over their robustness during long periods of simulation, in particular due to issues such as model drift and non-unique steady states. Previous studies have linked these to violation of conservation laws, but only explored those issues with respect to charge conservation in specific models. Here, we propose a general and systematic method of identifying conservation laws hidden in models of cardiac electrophysiology by using bond graphs, and develop a bond graph model of the cardiac action potential to study long-term behaviour. Bond graphs provide an explicit energy-based framework for modelling physical systems, which makes them well suited for examining conservation within electrophysiological models. We find that the charge conservation laws derived in previous studies are examples of the more general concept of a {extquoteleft}conserved moiety{extquoteright}. Conserved moieties explain model drift and non-unique steady states, generalizing the results from previous studies. The bond graph approach provides a rigorous method to check for drift and non-unique steady states in a wide range of cardiac action potential models, and can be extended to examine behaviours of other excitable systems.},
issn = {1364-5021},
journal = {Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences},
archiveprefix = {arXiv},
eprint = {1802.04548},
note = {Available at {arXiv:1802.04548}}
}
@article{GawCra18a,
author = {P. Gawthrop and E. J. Crampin},
journal = {IEEE Transactions on NanoBioscience},
title = {Bond Graph Representation of Chemical Reaction Networks},
year = 2018,
pages = {449-455},
volume = 17,
number = 4,
month = {October},
abstract = {The Bond Graph approach and the Chemical Reaction Network approach to modelling biomolecular systems developed independently. This paper brings together the two approaches by providing a bond graph interpretation of the chemical reaction network concept of complexes. Both closed and open systems are discussed. The method is illustrated using a simple enzyme-catalysed reaction and a trans-membrane transporter.},
keywords = {Chemicals;Junctions;Substrates;Standards;Nanobioscience;Biological system modeling;Open systems},
doi = {10.1109/TNB.2018.2876391},
issn = {1536-1241},
archiveprefix = {arXiv},
eprint = {1809.00449},
note = {Available at {arXiv:1809.00449}}
}
@article{PanGawTra19,
title = {A thermodynamic framework for modelling membrane transporters},
journal = {Journal of Theoretical Biology},
volume = 481,
pages = {10 - 23},
year = 2019,
issn = {0022-5193},
doi = {10.1016/j.jtbi.2018.09.034},
author = {Michael Pan and Peter J. Gawthrop and Kenneth Tran and Joseph Cursons and Edmund J. Crampin},
keywords = {Bond graph, Biochemistry, Chemical reaction network, Biomedical engineering, Systems biology},
abstract = {Membrane transporters contribute to the regulation of the internal environment of cells by translocating substrates across cell membranes. Like all physical systems, the behaviour of membrane transporters is constrained by the laws of thermodynamics. However, many mathematical models of transporters, especially those incorporated into whole-cell models, are not thermodynamically consistent, leading to unrealistic behaviour. In this paper we use a physics-based modelling framework, in which the transfer of energy is explicitly accounted for, to develop thermodynamically consistent models of transporters. We then apply this methodology to model two specific transporters: the cardiac sarcoplasmic/endoplasmic Ca2+ ATPase (SERCA) and the cardiac Na+/K+ ATPase.},
archiveprefix = {arXiv},
eprint = {1806.04341},
note = {Available at {arXiv:1806.04341}}
}
@article{GawCudCra20,
title = {Physically-Plausible Modelling of Biomolecular Systems: A Simplified, Energy-Based Model of the Mitochondrial Electron Transport Chain},
journal = {Journal of Theoretical Biology},
pages = 110223,
volume = 493,
year = 2020,
issn = {0022-5193},
doi = {10.1016/j.jtbi.2020.110223},
author = {Peter J. Gawthrop and Peter Cudmore and Edmund J. Crampin},
keywords = {Systems biology, Thermodynamical modelling, Bond graph, Computational biology},
abstract = {Advances in systems biology and whole-cell modelling demand increasingly comprehensive mathematical models of cellular biochemistry. Such models require the development of simplified representations of specific processes which capture essential biophysical features but without unnecessarily complexity. Recently there has been renewed interest in thermodynamically-based modelling of cellular processes. Here we present an approach to developing of simplified yet thermodynamically consistent (hence physically plausible) models which can readily be
incorporated into large scale biochemical
descriptions but which do not require full
mechanistic detail of the underlying processes. We
illustrate the approach through development of a simplified, physically plausible model of the mitochondrial electron transport chain and show that the simplified model behaves like the full system.}
}
@article{PanGawCur20,
author = {Michael Pan and Peter J. Gawthrop and Joseph Cursons and Kenneth Tran and Edmund J. Crampin},
title = {{The cardiac Na+/K+ ATPase: An updated, thermodynamically consistent model}},
year = 2020,
month = 8,
journal = {Physiome},
doi = {10.36903/physiome.12871070.v1},
abstract = {
The Na+/K+ATPase is an essential component of cardiac electrophysiology, maintaining physiological Na+ and K+ concentrations over successive heart beats. Terkildsen et al. (2007) developed a model of the ventricular myocyte Na+/K+ ATPase to study extracellular potassium accumulation during ischaemia, demonstrating the ability to recapitulate a wide range of experimental data, but unfortunately there was no archived code associated with the original manuscript. Here we detail an updated version of the model and provide CellML and MATLAB code to ensure reproducibility and reusability. We note some errors within the original formulation which have been corrected to ensure that the model is thermodynamically consistent, and although this required some reparameterisation, the resulting model still provides a good fit to experimental measurements that demonstrate the dependence of Na+/K+ ATPase pumping rate upon membrane voltage and metabolite concentrations. To demonstrate thermodynamic consistency we also developed a bond graph version of the model. We hope that these models will be useful for community efforts to assemble a whole-cell cardiomyocyte model which facilitates the investigation of cellular energetics.
}
}
@article{GawPan20,
author = {Gawthrop, Peter J.
and Pan, Michael},
title = {Network Thermodynamical Modeling of Bioelectrical Systems: A Bond Graph Approach},
journal = {Bioelectricity},
year = 2021,
month = {Mar},
day = 01,
publisher = {Mary Ann Liebert, Inc., publishers},
volume = 3,
number = 1,
pages = {3--13},
abstract = {Interactions among biomolecules, electrons, and protons are essential to many fundamental processes sustaining life. It is therefore of interest to build mathematical models of these bioelectrical processes not only to enhance understanding but also to enable computer models to complement in vitro and in vivo experiments. Such models can never be entirely accurate; it is nevertheless important that the models are compatible with physical principles. Network Thermodynamics, as implemented with bond graphs, provide one approach to creating physically compatible mathematical models of bioelectrical systems. This is illustrated using simple models of ion channels, redox reactions, proton pumps, and electrogenic membrane transporters thus demonstrating that the approach can be used to build mathematical and computer models of a wide range of bioelectrical systems.},
issn = {2576-3105},
doi = {10.1089/bioe.2020.0042},
note = {Published Online: 18 Dec 2020}
}
@article{Gaw21,
author = {P. J. {Gawthrop}},
journal = {IEEE Transactions on NanoBioscience},
title = {Energy-Based Modeling of the Feedback Control of Biomolecular Systems With Cyclic Flow Modulation},
year = 2021,
volume = 20,
number = 2,
pages = {183-192},
abstract = {Energy-based modelling brings engineering insight to the understanding of biomolecular systems. It is shown how well-established control engineering concepts, such as loop-gain, arise from energy feedback loops and are therefore amenable to control engineering insight. In particular, a novel method is introduced to allow the transfer function based approach of classical linear control to be utilised in the analysis of feedback systems modelled by network thermodynamics and thus amalgamate energy-based modelling with control systems analysis. The approach is illustrated using a class of metabolic cycles with activation and inhibition leading to the concept of Cyclic Flow Modulation.},
keywords = {Biological system modeling;Junctions;Transfer functions;Thermodynamics;Mathematical model;Feedback loop;Analytical models;Biological system modeling;computational systems biology;systems biology;negative feedback},
doi = {10.1109/TNB.2021.3058440},
issn = {1558-2639},
month = {April}
}
@article{GawPanCra21,
author = {Gawthrop, Peter J. and Pan, Michael and Crampin, Edmund J. },
title = {Modular dynamic biomolecular modelling with bond graphs: the unification of stoichiometry, thermodynamics, kinetics and data},
journal = {Journal of The Royal Society Interface},
volume = 18,
number = 181,
pages = 20210478,
year = 2021,
doi = {10.1098/rsif.2021.0478},
abstract = { Renewed interest in dynamic simulation models of biomolecular systems has arisen from advances in genome-wide measurement and applications of such models in biotechnology and synthetic biology. In particular, genome-scale models of cellular metabolism beyond the steady state are required in order to represent transient and dynamic regulatory properties of the system. Development of such whole-cell models requires new modelling approaches. Here, we propose the energy-based bond graph methodology, which integrates stoichiometric models with thermodynamic principles and kinetic modelling. We demonstrate how the bond graph approach intrinsically enforces thermodynamic constraints, provides a modular approach to modelling, and gives a basis for estimation of model parameters leading to dynamic models of biomolecular systems. The approach is illustrated using a well-established stoichiometric model of Escherichia coli and published experimental data. }
}
@article{PanGawCurCra21,
author = {Pan, Michael
and Gawthrop, Peter J.
and Cursons, Joseph
and Crampin, Edmund J.},
title = {Modular assembly of dynamic models in systems biology},
journal = {PLOS Computational Biology},
year = 2021,
month = {Oct},
day = 13,
publisher = {Public Library of Science},
volume = 17,
number = 10,
pages = {e1009513},
abstract = {Author summary The biochemistry within a cell is complex, being composed of numerous biomolecules and reactions. In order to develop fully detailed mathematical models of cells, smaller submodels need to be constructed and connected together. Software and standards can assist in this endeavour, but challenges remain in ensuring that submodels are both consistent with each other and consistent with the fundamental conservation laws of physics. In this paper, we propose a new approach using bond graphs from engineering. In this approach, connections between models are defined using physical conservation laws. We show that this approach is compatible with current software approaches in the field, and can therefore be readily used to incorporate physical consistency into existing model integration methodologies. We illustrate the utility of this approach in streamlining the development of models for a signalling network (the MAPK cascade) and a metabolic network (the glycolysis pathway). The advantage of this approach is that models can be developed in a scalable manner while also ensuring consistency with the laws of physics, enhancing the range of data available to train models. This approach can be used to quickly construct detailed and accurate models of cells, facilitating future advances in biotechnology and personalised medicine.},
doi = {10.1371/journal.pcbi.1009513}
}
@article{CudPanGaw21,
author = {Cudmore, Peter
and Pan, Michael
and Gawthrop, Peter J.
and Crampin, Edmund J.},
title = {Analysing and simulating energy-based models in biology using {BondGraphTools}},
journal = {The European Physical Journal E},
year = 2021,
month = {Dec},
day = 13,
volume = 44,
number = 12,
pages = 148,
abstract = {Like all physical systems, biological systems are constrained by the laws of physics. However, mathematical models of biochemistry frequently neglect the conservation of energy, leading to unrealistic behaviour. Energy-based models that are consistent with conservation of mass, charge and energy have the potential to aid the understanding of complex interactions between biological components, and are becoming easier to develop with recent advances in experimental measurements and databases. In this paper, we motivate the use of bond graphs (a modelling tool from engineering) for energy-based modelling and introduce, BondGraphTools, a Python library for constructing and analysing bond graph models. We use examples from biochemistry to illustrate how BondGraphTools can be used to automate model construction in systems biology while maintaining consistency with the laws of physics.},
issn = {1292-895X},
doi = {10.1140/epje/s10189-021-00152-4}
}
@article{MaiHunGaw22,
author = {Maini, Philip K.
and Hunter, Peter J.
and Gawthrop, Peter J.
and Smith, Nic P.},
title = {{Edmund John Crampin} 1973--2021},
journal = {Bulletin of Mathematical Biology},
year = 2022,
month = {Jan},
day = 29,
volume = 84,
number = 3,
pages = 35,
issn = {1522-9602},
doi = {10.1007/s11538-021-00987-0}
}
@article{GawPan22,
title = {Network thermodynamics of biological systems: A bond graph approach},
journal = {Mathematical Biosciences},
volume = 352,
pages = 108899,
year = 2022,
issn = {0025-5564},
doi = {https://doi.org/10.1016/j.mbs.2022.108899},
author = {Peter J. Gawthrop and Michael Pan},
keywords = {Systems biology, Bond graph, Energy-based, Photosynthesis, Electrochemical transduction},
abstract = {Edmund Crampin (1973-2021) was at the forefront of Systems Biology research and his work will influence the field for years to come. This paper brings together and summarises the seminal work of his group in applying energy-based bond graph methods to biological systems. In particular, this paper: (a) motivates the need to consider energy in modelling biology; (b) introduces bond graphs as a methodology for achieving this; (c) describes extensions to modelling electrochemical transduction; (d) outlines how bond graph models can be constructed in a modular manner and (e) describes stoichiometric approaches to deriving fundamental properties of reaction networks. These concepts are illustrated using a new bond graph model of photosynthesis in chloroplasts.}
}
@article{LorGolKamGaw22,
author = {Loram, Ian and Gollee, Henrik and Kamp, Cornelis van de and Gawthrop, Peter},
journal = {IEEE Transactions on Biomedical Engineering},
title = {Is intermittent control the source of the non-linear oscillatory component (0.2-2{Hz}) in human balance control?},
year = 2022,
pages = {1-1},
doi = {10.1109/TBME.2022.3174927}
}
@article{GawPan22a,
author = {Gawthrop, Peter J. and Pan, Michael },
title = {Energy-based advection modelling using bond graphs},
journal = {Journal of The Royal Society Interface},
volume = 19,
number = 195,
pages = 20220492,
year = 2022,
doi = {10.1098/rsif.2022.0492},
abstract = { Advection, the transport of a substance by the flow of a fluid, is a key process in biological systems. The energy-based bond graph approach to modelling chemical transformation within reaction networks is extended to include transport and thus advection. The approach is illustrated using a simple model of advection via circulating flow and by a simple pharmacokinetic model of anaesthetic gas uptake. This extension provides a physically consistent framework for linking advective flows with the fluxes associated with chemical reactions within the context of physiological systems in general and the human physiome in particular. }
}
@article{AlvGolGaw23,
author = {J Alberto Álvarez-Martín and Henrik Gollee and Peter J Gawthrop},
title = {Event-driven adaptive intermittent control applied to a rotational pendulum},
journal = {Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering},
volume = 237,
number = 6,
pages = {1000-1014},
year = 2023,
doi = {10.1177/09596518221147340},
abstract = { Intermittent control combines open-loop trajectories with feedback at discrete time instances determined by events. Among other applications, it has recently been used to model quiet standing in humans where the system was assumed to be time-invariant. This article expands this work to the time-variant case by introducing an adaptive intermittent controller that exploits the well-known self-tuning architecture of adaptive control with a Kalman filter to perform online state and parameter estimation. Simulation and experimental results using a rotational inverted pendulum show advantages of the intermittent controllers compared to continuous feedback control since the former can provide persistent excitation due to their internal triggering mechanism, even when no external reference changes or disturbances are applied. Moreover, the results show that the event thresholds of intermittent control can be used to adjust the degree of responsiveness of the adaptation in the system, becoming a tool to balance the trade-off between steady-state performance and flexibility against parametric changes, addressing the stability–plasticity dilemma of adaptation and learning in control. }
}
@article{GawPan23,
author = {Gawthrop, Peter J. and Pan, Michael },
title = {Sensitivity analysis of biochemical systems using bond graphs},
journal = {Journal of The Royal Society Interface},
volume = 20,
number = 204,
pages = 20230192,
year = 2023,
doi = {10.1098/rsif.2023.0192},
abstract = { The sensitivity of systems biology models to parameter variation can give insights into which parameters are most important for physiological function, and also direct efforts to estimate parameters. However, in general, kinetic models of biochemical systems do not remain thermodynamically consistent after perturbing parameters. To address this issue, we analyse the sensitivity of biological reaction networks in the context of a bond graph representation. We find that the parameter sensitivities can themselves be represented as bond graph components, mirroring potential mechanisms for controlling biochemistry. In particular, a sensitivity system is derived which re-expresses parameter variation as additional system inputs. The sensitivity system is then linearized with respect to these new inputs to derive a linear system which can be used to give local sensitivity to parameters in terms of linear system properties such as gain and time constant. This linear system can also be used to find so-called sloppy parameters in biological models. We verify our approach using a model of the Pentose Phosphate Pathway, confirming the reactions and metabolites most essential to maintaining the function of the pathway. }
}
@article{GawPanRaj25,
author = {Gawthrop, Peter J. and Pan, Michael and Rajagopal, Vijay },
title = {Energy-based modelling of single actin filament polymerization using bond graphs},
journal = {Journal of The Royal Society Interface},
volume = 22,
number = 222,
pages = 20240404,
year = 2025,
doi = {10.1098/rsif.2024.0404},
abstract = { Bond graphs provide an energy-based methodology for modelling complex systems hierarchically; at the moment, the method allows biological systems with both chemical and electrical subsystems to be modelled. Herein, the bond graph approach is extended to include chemomechanical transduction thus extending the range of biological systems to be modelled. Actin filament polymerization and force generation is used as an example of chemomechanical transduction, and it is shown that the TF (transformer) bond graph component provides a practical, and conceptually simple, alternative to the Brownian ratchet approach of Peskin, Odell, Oster and Mogilner. Furthermore, it is shown that the bond graph approach leads to the same equation as the Brownian ratchet approach in the simplest case. The approach is illustrated by showing that flexibility and non-normal incidence can be modelled by simply adding additional bond graph components and that compliance leads to non-convexity of the force–velocity curve. Energy flows are fundamental to life; for this reason, the energy-based approach is utilized to investigate the power transmission by the actin filament and its corresponding efficiency. The bond graph model is fitted to experimental data by adjusting the model physical parameters. }
}
@article{GawPan25,
author = {Gawthrop, Peter and Pan, Michael },
title = {Energy-based analysis of biochemical oscillators using bond graphs and linear control theory},
journal = {Royal Society Open Science},
volume = 12,
number = 4,
pages = 241791,
year = 2025,
doi = {10.1098/rsos.241791},
abstract = { The bond graph approach has been recognized as a useful conceptual basis for understanding the behaviour of living entities modelled as a system with hierarchical interacting parts exchanging energy. One such behaviour is oscillation, which underpins many essential biological functions. In this paper, energy-based modelling of biochemical systems using the bond graph approach is combined with classical feedback control theory to give a novel approach to the analysis, and potentially synthesis, of biochemical oscillators. It is shown that oscillation is dependent on the interplay between active and passive feedback and this interplay is formalized using classical frequency-response analysis of feedback systems. In particular, the phase margin is suggested as a simple scalar indicator of the presence or absence of oscillations; it is shown how this indicator can be used to investigate the effect of both the structure and parameters of biochemical system on oscillation. It follows that the combination of classical feedback control theory and the bond graph approach to systems biology gives a novel analysis and design methodology for biochemical oscillators. The approach is illustrated using an introductory example similar to the Goodwin oscillator, the Sel’kov model of glycolytic oscillations and the repressilator. }
}
@article{PanGawFar25,
author = {Pan, Michael and Gawthrop, Peter J. and Faria, Matthew and Johnston, Stuart T. },
title = {Thermodynamically consistent, reduced models of gene regulatory networks},
journal = {Royal Society Open Science},
volume = 12,
number = 7,
pages = 241725,
year = 2025,
doi = {10.1098/rsos.241725},
abstract = { Synthetic biology aims to engineer novel functionalities
into biological systems. While the approach has been
predominantly applied to single cells, a richer set
of biological phenomena can be engineered by
applying synthetic biology to cell populations. To
rationally design cell populations, we require
mathematical models that link between intracellular
biochemistry and intercellular interactions. In this
study, we develop a kinetic model of gene expression
that is suitable for incorporation into agent-based
models of cell populations. To be scalable to large
cell populations, models of gene expression should
be both computationally efficient and compliant with
the laws of physics. We satisfy the first
requirement by applying a model reduction scheme to
translation and the second requirement by
formulating models using bond graphs, a modelling
approach that ensures thermodynamic consistency. Our
reduced model is significantly faster to simulate
than the full model and reproduces important
behaviours of the full model. We couple separate
models of gene expression to build models of the
toggle switch and repressilator. With these models,
we explore the effects of resource availability and
cell-to-cell heterogeneity on circuit behaviour. The
modelling approaches developed here are a bridge
towards engineering collective cell behaviours such
as synchronization and division of labour.
}
}
@article{MalGugHun25,
author = {Malecki, Cassandra and Guglielmi, Giovanni and Hunter, Benjamin and Harney, Dylan and Koay, Yen Chin and Don, Anthony. S. and Han, Oscar and Khor, Jasmine and Nguyen, Lisa and Pan, Michael and Gawthrop, Peter and Isles, Nathan and Chung, Joshua and Hume, Robert. D. and Taper, Matthew and Wang, XiaoSuo and Larance, Mark and Spill, Fabian and Rajagopal, Vijay and O’Sullivan, John F. and Lal, Sean},
title = {The Human Cardiac “Age-OME”: Age-Specific Changes in Myocardial Molecular Expression},
journal = {Aging Cell},
volume = {n/a},
number = {n/a},
year = 2025,
pages = {e70219},
keywords = {ageing, age-OME, excitation-contraction coupling, human heart, metabolism, omics},
doi = {https://doi.org/10.1111/acel.70219},
note = {e70219 ACE-24-1128-RAr},
abstract = {Ageing is one of the most significant risk factors for heart disease; however, it is still not clear how the human heart changes with age. Taking advantage of a unique set of pre-mortem, cryopreserved, non-diseased human hearts, we performed omics analyses (transcriptomics, proteomics, metabolomics, and lipidomics), coupled with biologically informed computational modelling in younger (<25~years~old) and older hearts (>50~years~old) to describe the molecular landscape of human cardiac ageing. In older hearts, we observed a downregulation of proteins involved in calcium signalling and the contractile apparatus. Furthermore, we found a potential dysregulation of central carbon generation of fuel, glycolysis, and fatty acids oxidation, along with an increase in long-chain fatty acids. This study presents and analyses the first molecular data set of normal human cardiac ageing, which has relevant implications for understanding the human cardiac ageing process and the development of age-related heart disease.}
}
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