Robust self-tuning PID-like control with a filter for a class of discrete time systems

Most real processes are high order and hence, an approximate model is usually used in practice. Considering the mismatching of model-process order, in this paper, a robust self-tuning PID-like controller is proposed by combining a pole assignment self-tuning PID controller with a filter. To design the PID-like controller, a reduced order model is introduced, whose linear parameters are identified by a normalized project algorithm with deadzone. The gains of the PID-like controller are obtained by pole assignment, which together with other parameters are tuned on-line according to the certainty equivalent principle. By resorting to time varying operation, the bounded input bounded output (BIBO) stability conditions and convergence conditions of the closed-loop system are presented.