Loop transfer recovery design with proportional integral observer based on H^INF optimal observation

A loop transfer recovery (LTR) design method with a proportional integral (PI) observer is proposed. It is based on the H^∞ optimal observation via factorization approach. A general controller structure consisting of a robust linear functional observer and state feedback is used in the feedback control system. A parameterization for all PI observers is given. The interconnection between the optimal LTR problem and H^∞ optimal observation problem using PI observer for the given system is shown. Analysis indicates that they are exactly the same. Based on the results of the H^∞ optimal observation, the optimal LTR design is solved in the general framework of the H^∞ optimization. The proposed method is effective for both minimum phase and non-minimum phase systems. The loop transfer and the disturbance attenuation properties can be recovered simultaneously using this method. A systematic design procedure of optimal LTR based on H^∞ optimization is presented.