Design of decentralized projective controls for disturbance rejection

A two-stage design problem is formulated to achieve disturbance rejection using low-order decentralized controllers. Using the H_∞-optimal state feedback solutions as the reference, the authors parameterize all decentralized controllers of a given order retaining the dominant poles in the closed-loop system. Using a Frobenius-Hankel norm-minimization approach, they determine the free parameters in the parameterization that can be used to place the remaining zeros and poles for disturbance rejection. The procedure is illustrated on a seventh-order example for which two first-order controllers were designed