Realtime tracking in five degrees of freedom using two writs-mounted laser range finders

The results of experiments in real-time tracking of moving objects using wrist-mounted sensors are presented. Two laser range finders were mounted orthogonal to each other on the wrist of a six-degree-of-freedom PUMA robot. The objective is to have the robot end-effector maintain a constant position and orientation with respect to a flat object moving in 3D space in the field of view of the range finders. Sensory feedback from the range finders is used to servocontrol the robot such that its trajectory is similar to that of the moving object in five degrees of freedom. The algorithms for this application are implemented in C and run on four Motorola MC68020 processors with the Harmony operating system. Tracking is done with maximum linear and angular speeds of the target object being 25 cm/s and 0.5 rad/s, respectively. The robot is capable of maintaining the required pose with respect to the object at these speeds with a small lag due to data-collection time. The acceleration/deceleration and the maximum speed of the robot trajectory are varied depending on the speed of the moving object being tracked to yield different tracking behaviors. A performance study of the tracking experiment is presented