Selection of Optimal Axis Configurations in a Robot Path

A method is presented to minimize execution time for a robot task consisting of motions between a series of end effector locations. Many robots can usually reach a given end effector cartesian location and orientation in several different axis configurations. Robot computer controllers, such as for the PUMA 560 using VAL-II, often choose a configuration for the motion destination similar to the configuration of the starting location in order to avoid potentially unsafe configuration changes during the motion. Shorter motion times are often possible if configuration changes are allowed during the motion. In this work, a dynamic programming method is used to determine a configuration sequence that gives the minimum task time. A simple motion model is used to predict the individual motion times between locations. It is shown that for the PUMA 560 robot the method results in approximately 4 to 20 percent shorter path execution times than are produced by the native robot controller.