Novel non linear PD controller for the positioning system of a 2D Automated Visual Inspection Machine for Quality Control of SMD

In this paper we present the design and the real time implementation of a nonlinear PD type controller designed to improve the performance of an electromechanical positioning system of a 2D automatic visual inspection machine. We describe the control function and analyse the stability of the closed loop system to determine the feasibility of a tune up process. This control law is proposed to solve some of the problems presented by commercial actuators used in accurate positioning tasks. This controller reduces the steady state error without introducing an integral action to the closed loop and imposes a limit to the torques applied to the actuator below the recommended specification without degrading the transitory responses of the closed loop system. We show the effectiveness of the proposed controller with real time experimental results obtained using an industrial embedded system with restricted facilities