The Prediction of the Angular Transmission Error of a Harmonic Drive by Measuring Noncontact Tooth Profile and Considering Three-dimensional Tooth Engagement

The importance of robots is growing in manufacturing of the new normal era caused by the 4th industrial revolution and the pandemic. Harmonic drive is widely used as a precision reducer for the joint motion control of industrial robots. The angular transmission error (ATE) is an important performance indicator that greatly affects the position accuracy and vibration of a robot. This paper presents a novel method of predicting the ATE of a harmonic drive by measuring noncontact tooth profile and considering 3-dimensional tooth engagement. The tooth profile of the harmonic drive was measured with a commercial noncontact coordinate measuring machine, and the tooth pitch error was extracted using several mathematical techniques. The ATE considering 3D tooth engagement was predicted by introducing a triangular engagement coefficient. The ATE errors of 9 harmonic drives assembled with 3 flex splines (F/S) and 3 circular splines (C/S) were predicted and the superiority of the proposed method was verified by experimentally measuring their ATE.