MIMO controller synthesis with integral-action integrity

A controller synthesis method is presented for closed-loop stability and asymptotic tracking of step input references with zero steady-state error. Integral-action is achieved in two design steps starting with any stabilizing controller and adding a PID-controller in a configuration that guarantees robust stability and tracking. The proposed design has integral-action integrity, where closed-loop stability is maintained even when any of the proportional, integral, or derivative terms are removed or the entire PID-controller is limited by a constant gain matrix. The integral constant can be switched off when integral-action is not wanted. 2007 Elsevier Ltd. All rights reserved.