Generalized sampled-data hold functions for robust multivariable tracking and disturbance rejection

A new design procedure for a multivariable sampled-data output feedback controller with generalized hold function is proposed. The controller can be designed for different operating points simultaneously. The design of the hold function is carried out in two steps: first the closed-loop discrete-time behaviour is determined by choosing a suitable output injection gain; integral action is incorporated to guarantee zero steady-state error. In a second step this discrete-time behaviour is approximately realised by output feedback with generalized hold. Minimization of a quadratic performance index simultaneously for all operating points yields hold functions with good intersample behaviour. A practical design example and experimental results illustrate the proposed method.