On ∞ Controllers with Integral Action: an Experimental Evaluation

This paper presents an experimental evaluation of two design methods for including integral action in ∞ controllers. There are two basic possibilities for doing that: (i) the specification of an integral weighting of the regulation error; or (ii) the direct inclusion of an integrator in series with the plant control input. The GS/T mixed sensitivity scheme has been employed, in order to avoid the generalized plant transfer matrix inversion. Alternative (i) is performed via an approximation that takes the generalized plant poles out of the imaginary axis (namely, the pole at origin). Such approximation is necessary to allow the Riccati equation to have a solution. An approximation procedure is proposed here, based on a linear mapping of the generalized plant model into another model close to the original one, and the inverse (approximate) mapping of the resulting controller. Alternative (ii) is implemented via an LMI (Linear Matrix Inequalities) algorithm. The experimental data suggests that the integral weighting specification leads to better results, possibly due to the lower order of the resulting controller.