VISUAL COMPLIANCE - TASK-DIRECTED VISUAL SERVO CONTROL

This paper introduces visual compliance, a new vision-based control sc heme that lends itself to task-level specification of manipulation goa ls. Visual compliance is effected by a hybrid vision/position control structure. Specifically, the two degrees of freedom parallel to the im age plane of a supervisory camera are controlled using visual feedback , and the remaining degree of freedom (perpendicular to the camera ima ge plane) is controlled using position feedback provided by the robot joint encoders. With visual compliance, the motion of the end effector is constrained so that the tool center of the end effector maintains ''contact'' with a specified projection ray of the imaging system. Thi s type of constrained motion can be exploited for grasping, parts mati ng, and assembly. We begin by deriving the projection equations for th e vision system. We then derive equations used to position the manipul ator prior to the execution of visual compliant motion. Following this , we derive the hybrid Jacobian matrix that is used to effect visual c ompliance. Experimental results are given for a number of scenarios, i ncluding grasping using visual compliance.