Introduction

Abstract

Any model of a physical system will never be a true representation of that system. Often this is primarily because there are characteristics which can-not easily be modelled, and some approximation must be used. In any case, however detailed the model, there will always be modelling inaccuracies. In practice there is also a trade-off to be made between model complexity and model accuracy in that a simple model is easier to simulate and use for de-sign. Robustness to modelling inaccuracy is therefore a vital characteristic required of a controller.