Output tracking control of discrete-time nonlinear systems by adaptive PID based on output feedback passivity

In this paper, we propose a design scheme of an adaptive PID tracking control system for discrete-time nonlinear SISO systems. The proposed method utilizes the OFSP properties of the controlled system, so that the stability of the resulting adaptive control system can be guaranteed with certainty. A robust adaptive PID design scheme for the OFSP augmented system with a parallel feedforward compensator without causality problems was developed by introducing an adaptive NN feedforward control signal.