Robust Tracking for the Open-Loop Unstable Process with Time Delay by Combining PID type-p and Inner Compensators

The robustly tracking control, which is to design the stabilizing controllers such that the system output robustly tracks a given reference signal in the presence of certain disturbances [1], is considered for the open-loop unstable processes with time-delay. The PID type-p closed loop control system (p-integrators in the open-loop transfer function) is expected to track both reference signals faster and eliminate higher order errors at steady state [7]. Smith predictor and inner compensator are used to stabilize the unstable process with time delay. A new approach, combining PID type-p with inner compensators, is to stabilize the unstable poles, time delay, and to achieve tracking reference signal and eliminate higher order errors at steady state very well. Examples are presented to illustrate this proposed approach.