All publications by Gawthrop in 2002

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. A biquadratic active filter and an electromechanical control system are used to illustrate the approach.

A modern view of minimum variance control is presented by generalising the notion of prediction and considering both discrete-time and continuous-time formulations. The relation to other control design methods is also presented.

Self-tuning control is a simple method for controlling systems with uncertainty which has a long history of successful application

It is shown that the concept of intermittent control, to be found in the physiological literature, provides a useful alternative to both continuous-time and discrete-time approaches to control system design. In particular an intermittent version of predictive pole placement (PPP) is presented. This intermittent predictive pole placement algorithm is illustrated in the context of a non-linear pendulum-on-cart system.

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.

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.

This paper examines two classes of algorithms that estimate a continuous time ARX type of models from discrete data: one is based on infinite impulse response (IIR) filters while the other is based on finite impulse response (FIR) filters. The IIR filters use continuous time state variable filters, and discretisation is performed on the filtered derivatives. In contrast, the FIR filters are in a discrete form with carefully chosen coefficients to approximate the derivatives of the continuous time variables. The strength and weakness of each approach are discussed and demonstrated by a set of simulation examples.

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 emphasised. 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 to a well-known frequency response method.