Abstract
The purpose of this paper is to design a nonlinear PID controller for trajectory tracking of a manipulator robot. The objective is to develop a PID controller having high performances for the controllability and the stability of the manipulator. Moreover, the controller should be easy to implement. In a first step a PID plus a feedforward controller has been developed and implemented on a SCARA robot. In the second step and in order to increase performances of the developed control law, an improving version has been developed by adopting nonlinear gains. Simulation results show the effectiveness of the control law in particular in the presence of variable gains.