Suppression of vibration due to transmission error of harmonic drives using peak filter with acceleration feedback

Harmonic drives are widely used in robotics and precision positioning systems because of their unique properties such as near-zero backlash, high speed reduction ratio. However, they possess a periodic positioning error known as the transmission error and it produces a speed ripple on the gear output shaft. This is critical when the frequency of the speed variation coincides with the resonant frequency of the control system. This paper presents a speed control system to suppress the vibrations caused by the transmission error from harmonic drives. First, a new analysis scheme is proposed to analyze the effects of the transmission error. Next, a peak filter using load side acceleration information is designed and added into the servo loop in parallel with the existing controller. Simulation and experimental results show that the proposed system regulates the load side velocity satisfactorily and suppresses the vibration caused by the transmission error effectively.