Improving force controlled planar contour following using on-line 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 on-line from an eye-in-hand camera image, results in a faster or more accurate executed task. However, keeping the contour in the camera field 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 orientation of the task frame can then be controlled independent of the end effector. Experimental results are presented to validate the approach.