Sliding mode schemes using output information with application to heating plant problems.

This thesis considers the problem of developing sliding mode output tracking controllers for uncertain systems when output information alone is available. Two different approaches to controller design are proposed. The first approach is an observer based scheme which utilizes integral action. A new framework is proposed for the design of a class of sliding mode observers. The attainment of a canonical form, which is central to the framework, is a necessary and sufficient condition for the existence of a class of observers insensitive to matched uncertainty. The results supersede previous work in this area which necessitated checking the validity of a structural constraint between the state space matrices of the system. A formal analysis is undertaken of the combined plant/observer dynamics obtained when using a sliding mode control law incorporating integral action. It is demonstrated that the combined system is quadratically stable, despite the presence of a class of bounded matched uncertainty. Furthermore, the control law and the observer system can be designed independently; in other words, the 'separation principle' for linear systems also holds for this class of uncertain system and controller/observer pair. The second approach considers an output feedback stabilization problem where the class of hyperplanes and control laws considered is restricted to those which require only output information. The analysis is performed in essentially the same framework as that developed for the sliding mode observer. It enables the class of systems considered by other workers in this field to be extended and provides a practical realizable controller which requires no additional assumptions. These results are used in a model-reference framework to obtain a tracking controller. Successful attempts to implement these new theoretical ideas on an experimental furnace at the Gas Research Centre at Loughborough are documented. A single-input single-output sliding mode scheme to control temperature is described. Details are given of a more ambitious, multivariable scheme to regulate both temperature and excess oxygen by the manipulation of the fuel and air flows.