Manipulator control using the configuration space method

Abstract

The throughput of a manipulation process depends upon the arm's speed of operation, but many existing controllers provide accurate trajectory control only at low or moderate velocities. We propose a control method that explicitly compensates for configuration‐dependent gravity, acceleration, and velocity forces ‐ the latter being especially important during rapid simultaneous motions of a number of joints. A tabular form of the equations of motion is used in real‐time in conjunction with a configuration space memory organized by positional variables. The contents of the memory are pre‐computed only once for each manipulator and are usable for all possible movements. A planned implementation of this method for the Stanford Schienman arm that uses about 250K memory locations and requires about n3 + 3n2 arithmetic operations per evaluation is discussed, where n is the number of degrees of freedom of the device.