Adjustment of robot joint gears using encoder velocity and position information

A new technique for the adjustment of joint gears in industrial robots is presented. Band-limited random excitation signals were injected into the drive system of the joint under test, and both the actuator shaft velocity and position were monitored. The coherence functions between the voltage at the terminals of the electric actuator and the position and velocity signals were determined. The change in the coherence functions was studied for various joint gear settings. An algorithm is proposed for determining the gear setting which results in the most linear operation of the joint drive system. This algorithm was tested on the adjustment of the gears of the wrist rotation joint of a PUMA 560 robot arm.