Full Range Torque Estimation on Drivetrains with Strain Wave Gears

This paper consider sensorless joint torque esti- mation for kinesthetic teaching on industrial robots with strain wave gears. We show that a simple torsional compliance model of the gear can be used to augment the joint torque estimated by a generalized momentum observer to obtain accurate joint torque estimates when the system has zero momentum. This is accomplished by providing a framework for joining the two joint torque estimates and showing that the combined method has an improved Root Mean Square Error (RMSE) of 39%, as compared to the momentum observer, when the model pa- rameters of the torsional compliance model are computed from the gear’s datasheet and an improved Root Mean Square Error (RMSE) of 49% when the model parameters are estimated on data from the joint.