Controller structure selection using the reduced structure control methodology

Almost all multivariable design techniques impose a fixed structure on the final controller. This may be centralised or (block) decentralised, but it is typically the case that the structure is either not adequate or excessive. This work concerns an alternative design method whereby the controller structure is not fixed, but instead is also a design objective. Based on this a generic cost function is determined where both the structure of the controller and the performance of the resulting closed loop system appear as minimisation terms. It has been shown that there exists an optimal weighting such that the optimisation of the weighted sum of these two terms will always result in a unique reduced structure controller. The methodology is then successfully applied to the model of a gas-turbine