Visual servoing using image features defined upon geometrical primitives

The image features used in visual servoing or tracking are generally the coordinates of image points. In this paper, we present how it is possible to define more complex visual features based on geometrical primitives such as lines, spheres and cylinders. Using such features enables one to realize a large variety of robotics tasks depending on the desired virtual linkage between the camera and the objects in the scene. We then describe a control scheme in closed loop with respect to these image features which is based on the task function approach. This scheme combines the regulation of the selected vision-based task with the minimization of a secondary cost function, such as a trajectory tracking using the robot degrees of freedom not constrained by the vision-based task. We finally present real time experimental results obtained with a camera mounted on the end-effector of a 6-DOF robot