Application of passive velocity field control to robot contour following problems

In contour following applications, the various degrees of freedom of the robot have to be well coordinated but very often, the speed at which the contour is followed is not critical. In this paper, we propose a control methodology in which the coordination aspect is made explicit by specifying the task using a velocity field on the manifold related to the configuration space of the robot. The passive control law proposed in Li and Horowitz (1995) and Li (1995) is used so that the defined velocity field is tracked and the robot traces out the desired contour. Using this control scheme, timing along the contour can be naturally varied on-line by a self pacing scheme so that the tracking performance can be improved. Robustness results, and the geometry of the closed loop dynamics, in terms of a new covariant derivative, not previously presented are given. The experimental results of contour following using the proposed scheme applied to a robot following a Lissajous contour are presented.