Adaptive Disturbance Cancellation for Indirect Drive Robots Using Joint Sensing Information

Harmonic drives are widely used in robotics and precision positioning systems because of their unique properties such as near-zero backlash, and high speed reduction ratio. However, they possess a periodic positioning error known as the transmission error and it causes vibrations on the output shaft of the gear. In this paper, an adaptive compensation scheme for the transmission error in indirect drive robots is proposed. To enhance the performance and to avoid deteriorating the transient response, two modifications are introduced to the basic compensation structure. The load side acceleration information is adopted in real-time control to measure and to reject the load side oscillations. Also, it is used in the adaptation laws to generate the compensation signal that cancels the vibrations on the load side. Experimental results show the effectiveness of the proposed schemes and the improvement in load side performance.