2 DOF adaptive PID control with a parallel feedforward compensator for nonlinear systems

In this paper, we propose a design method of an adaptive PID controller based on output feedback for nonlinear systems with a higher order relative degree and disturbances. To realize an adaptive PID control system, we introduce a PFC for a nonlinear system which does not satisfy OFEP (Output Feedback Exponentially Passive) conditions and design an adaptive feedforward input with a structure of RBF (Radial Basis Function) neural networks in order to remove the steady-state bias error from the PFC output. The proposed method can design a robust adaptive PID controller with higher accuracy on tracking control.