IN-SITU MEASUREMENT OF MOTOR ELECTRICAL CONSTANTS

Motor torque constant is an important parameter in modeling and contro lling a robot axis. In practice this parameter can vary considerably f rom the manufacturer's specification, if available, and this makes it desirable to characterise individual motors, Traditional techniques re quire that the motor can be removed from the robot for testing, or tha t an elaborate technique involving weights and pulleys be employed. Th is paper describes a novel method for measuring the torque constant of robot servo motors in situ and is based on the equivalence of motor t orque and back EMF constants. It requires a very simple experimental p rocedure, utilizes existing axis position sensors, and eliminates effe cts due to static friction and joint cross coupling. A straightforward extension to this approach can provide a measurement of motor armatur e impedance. Experimental results obtained for a Puma 560 are discusse d and compared with other published results.