Visual Servoing. Nonlinear Observer Approach.

Abstract

The visual servo system is a robotic servo mechanism that incorporates the vision sensor in the feedback loop. The conventional static look and move scheme is not suitable for visual servoing because the visual servoing is used mainly in dynamically chaning environments. Although the dynamic couplings exist between the robot and the camera, previously proposed schemes neglected the robot dynamics. Therefore, they are not sufficient for real-time dynamic visual servoing. This paper proposes a nonlinear controller and a nonlinear observer for the visual servo system. Also a consideration on the tracking condition is given. The nonlinear controller compensates the robot and camera characteristics. The nonlinear observer estimates the object velocity and predicts the object motion. The observer-based control scheme is proved to be asymptotically stabile. Moreover, the effectiveness of the nonlinear observer approach is verified by simulations and experiments on a two link direct drive robot.