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 conditions simultaneously. The design of the hold function is carried out in two steps: first the closed-loop discrete-time behaviour is designed by choosing a suitable output injection gain; integral action is incorporated to guarantee zero steady-state error. In a second step the output injection gain is approximately realized by output feedback with generalized hold. Minimization of a quadratic performance index simultaneously for all operating conditions allows a compromise between good intersample behaviour and closeness to the original design. A numerical example and experimental results illustrate the proposed method.