Tracking and disturbance rejection in non-minimum phase systems

This paper concerns with the problems of tracking control and disturbance rejection for two types of non-minimum phase (NMP) systems associated with the right half plane (RHP) zeroes and with time delay, respectively. As the achievable closed-loop bandwidth for such systems is usually very limited, obtaining good tracking and disturbance rejection becomes great challenges in the control design. For disturbance rejection, this paper mainly focuses on the method of active disturbance rejection control (ADRC), where modifications in tuning, in ESO and in ADRC structure are made to make the solutions more effective for the NMP systems; for fast tracking, a unique feedforward design is combined with ADRC solution to overcome the bandwidth limitation. The proposed methods are validated in simulation with satisfactory performance and give practitioners a set of tools to deal with the problems of the NMP systems.