Robust friction compensator for harmonic drive transmission

The torque control of harmonic drive system is examined in detail. An empirical nominal model for the system is obtained through experimental frequency response estimates, and the deviation of the system from the model is encapsulated by multiplicative uncertainty. A robust torque controller is subsequently designed in an H_∞ -framework and implemented using Kalman filtered torque estimates. Exceptional performance results are obtained from the time and frequency response of the closed-loop system. To further improve the performance of the system, a model-based friction-compensation algorithm is implemented in addition to the robust torque control. It is shown that the friction-compensation reduced the model uncertainty at low frequencies. Hence, the performance of the closed-loop system is improved for tracking signals with low-frequency content