2-DOF control system with PID/spl times/(n-1) stage PD controller

This paper presents a design technique for the two degree of freedom (2-DOF) control system using PID (Proportional-Integral-Derivative)/spl times/(n-1) stage PD as a cascade controller for the n/sup th/ order plant. It is intended to satisfy both transient and steady state response specifications based on the root locus approach. This controller can be used instead of a conventional PID controller to obtain better performance without relying upon any tuning methods. The overall system is approximated as a stable and robust second order system. The performances of the control system are satisfied by this design technique without any adjustment. The cascade controller gain can be adjusted to meet faster responses with little or no overshoot. The simulation results show that the desired performances are achieved. The merit of this approach for the system with uncertain parameters is also shown.