Variable structure PID based visual servoing for robotic tracking and manipulation

This paper presents a practical experiment on the use of visual servoing for robotic tracking and manipulation of objects moving on a plane. In this work, the image is acquired from the camera mounted on the end-effector of a 6 DOF industrial robot, and processed on a standard PC-based vision system in order to close the visual servoing loop with a PID based controller. The PID has been implemented with a variable structure, modified according to the estimated velocity of the target, in order to achieve a good step response and to eliminate steady-state error with a moving target. The possibility to perform a stable tracking and to estimate the target dynamics allows also to grasp the object with a prediction based trajectory planning.