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Beckman Institute Department of Electrical and Computer Engineering University of Illinois, Urbana
A major limitation of current robotic systems is their inability to cope effectively with uncertainty. In this presentation, I will introduce visual compliance, a new uncertainty-tolerant, vision-based control scheme that lends itself to task-level specification of manipulation goals. Visual compliance is effected by a hybrid vision/position control structure. Specifically, the two degrees of freedom parallel to the image plane of a supervisory camera are controlled using visual feedback, and the remaining degree of freedom (perpendicular to the camera image 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. This type of constrained motion can be exploited for grasping, parts mating, and assembly.
There is an obvious analogy between physical compliance (using force control) and visual compliance. This suggests that techniques used for fine-motion planning can be extended to exploit visual compliance. In particular, I will show how the backprojection approach to fine-motion planning can be extended to exploit visual compliance. The key to this approach is the derivation of a configuration space representation of visual constraint surfaces, which permits us to include visual constraint surfaces as boundaries of the directional backprojection. Further, an examination of the behavior of visual constraints as a function of the direction of the commanded velocity enables us to determine new criteria for critical velocity orientations (i.e. velocity orientations at which the topology of the directional backprojection, including visual constraint surfaces, might change).
Host: Mike Erdmann For an appointment with the speaker, please contact Phyllis Pomerantz at email@example.com or x8-7897