Improving force controlled planar contour following using online eye-in-hand vision based feedforward

The limited bandwidth of sensor-based feedback control restricts the execution speed of a force controlled planar contour following task, if the shape of the workpiece is unknown. This paper shows how appropriate feedforward control of the task frame orientation, calculated online from an eye-in-hand camera image, results in a higher quality (i.e. faster and/or more accurate) task execution. However, keeping the contour in the camera held of view in addition to maintaining a force controlled contact, imposes additional requirements on the controller. This double control problem is specified in the task frame formalism and executed in a hybrid position/force control environment. It is solved using the redundancy for the rotation in the plane, which exists for rotational symmetric tools. The key in this solution is (continuously) redefining the relation between the task frame and the end effector. Experimental results are presented to validate the approach.