Partial decoupling using H∞ methods

The authors present a method for designing a serial controller for a linear time-invariant finite-dimensional multiple input multiple output (MIMO) closed-loop system. The proposed design method enables partial decoupling of the closed-loop system response. It is based on H_∞ techniques for design of robust control systems. The resulting controller renders robustness to noise and model uncertainties, as well as decoupling of the closed-loop system. A set of sufficient and necessary conditions is presented for the existence of such a controller as well as the algorithm for computing the controller. Its decoupling and robustness properties are enforced using two criteria: diagonal dominance of the closed-loop transfer function matrix and the ratio between its diagonal terms and the sum of nondiagonal terms