Design of Optimal Robust Steady-state Tracking Controller under Coprime Factor Perturbations

The robust steady-state tracking problem subjected to coprime factor perturbations and unknown external bounded disturbance is addressed.An exact formula for computing the worst-possible steady-state absolute value of the control error is proposed by using Youla parameterization.With this formula,it is shown that the design of optimal robust steady-state tracking controller is reduced to 1 optimal robust controller design ensuring robust stability.