An ℋ_∞ control system design method for parameter sensitivity reduction

There are two types of uncertainty in a system to be controlled: parameter errors and unstructured uncertainty. Conventional ℋ_∞ control synthesis in the presence of unstructured uncertainty has been developed on the basis of frequency‐domain criteria using the state‐space method. It is difficult to consider the sensitivity to parameter errors in the frequency domain, however. In this paper, the authors propose an ℋ_∞ controller design method which can cope with parameter errors by introducing a trajectory sensitivity model into the conventional ℋ_∞ controller design method. It is also shown that the obtained controller is equivalent to a dynamic state feedback controller whose order becomes high. Thus, controller reduction is adopted.