| dc.description.abstract | This paper describes an inexpensive stereo visual servoing system for a commercial 6-axis industrial robot manipulator arm and its standard industrial controller. Visual servoing is by nature a reactive control scheme. It enables a manipulator to reach toward, and contact an object whose pose could be dynamic. Standard industrial robot controllers are, however, designed to be preprogrammed manually to enable point-to-point repetitive motion of a manipulator arm. Reactivity requires preemptive control – the target position of the manipulator must be changeable mid trajectory, not after a preprogrammed motion is completed. Visual servoing with a nonpreemptive controller requires continual, automatic reprogramming during task execution. The system described herein does this by running the vision system and the robot controller independently in parallel. The two are coupled through message passing that updates the visual target’s position as quickly as it can be computed so that a series of short trajectories will cause the robot’s motion to be effectively reactive. The visual system is inexpensive; it uses a standard PC workstation and a pair of webcams for stereopsis. Object detection and tracking are performed on the PC by combining stereo-optic 3D position estimation with color modeling. The hardware testbed comprised a PC, a pair of Logitech 9000 webcams, and a Yaskawa-Motoman HP3JC robot with an NXC-100 controller. The vision system design, calibration, and coupling with the robot are described. Experiments are reported that demonstrate capabilities of the system. | |
