Robust PID controller design for non-minimum phase time delay systems

A robust PID controller for a non-minimum phase system subject to uncertain delay time is presented in this paper. Utilizing the gain-phase margin tes ter method, a specification-oriented parameter region in the parameter plan e that characterizes all admissible controller coefficient sets can be obta ined. The PID controller gains are then directly selected from the paramete r region. Henceforth, the designed controller can guarantee the system at l east a pre-specified safety margin to compensate for the instability induce d by the time delay. A compromise between the robustness and tracking perfo rmance of the system in the presence of time delay is achieved. Simulation results indicate that the proposed method performs a good time response, an d robustness is obtained effectively. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.