A Switching Notch Filter for Reducing the Torque Ripple Caused by a Harmonic Drive in a Joint Torque Sensor

하모닉 드라이브의 토크리플 감소를 위한 조인트 토크센서용 스위칭 노치필터

  • Received : 2010.08.10
  • Accepted : 2011.04.26
  • Published : 2011.07.01


Harmonic drives have been widely used in combination with joint torque sensors in order to facilitate accurate manipulator control. A harmonic drive causes a torque ripple because of its structural characteristics, and this torque ripple tends to deteriorate the performance of a controller or observer that uses torque sensors. This paper proposes a switching notch filter for reducing the torque ripple caused by a harmonic drive in a joint torque sensor; the functioning of this filter is based on the relationship between the frequency components of the torque ripple and the rotational velocity of the harmonic drive. The proposed switching notch filter is advantageous in that it requires less computational load and does not necessitate additional circuits or structures. Various experiments demonstrate that the proposed filter has good filtering performance, fast response, and good switching stability.


  1. Timothy, D. T. and Warren, P. S., 1996, "A Nonlinear Model of Harmonic Drive Gear Transmission," IEEE Int. Conf. on Robotics and Automation, Vol. 12, No. 3, pp. 368-374.
  2. Richard, D., Fathi, H. G. and Prasanna, S. G., 2003, "A New Dynamic Model of Hysteresis in Harmonic Drives," IEEE Trans. on Industrial electronics, Vol. 50, No. 6, pp. 1165-1171.
  3. Ivan, G., Tamotsu, N. and Masashi, H., 2001, "Ripple Compensation for Torque Sensors Built into Harmonic Drives," IEEE Trans. on instrumentation and measurement, Vol. 50, No. 1, pp. 117-122.
  4. Jonathon, W. S. and Richard, F., 2006, "Improved Torque Fidelity in Harmonic Drive Sensors Through the Union of Two Existing Strategies," IEEE/ASME Trans. on mechatronics, Vol. 11, No. 4, pp. 457-461.
  5. Hamid, D. T. and Belanger P. R., 1998, "Torque Ripple and Misalignment Torque Compensation for the Built-In Torque Sensor of Harmonic Drive Systems," IEEE trans. on instrumentation and measurement, Vol. 47, No. 1, pp. 309-315.
  6. Thede, L., 2004, Practical Analog and Digital Filter Design, Artech House, Boston, pp. 98-103.
  7. Zhen Y. Z., Masayoshi. T. and Satoru. I., 1993, "Fuzzy Gain Scheduling of PID Controllers," IEEE Trans. on Systems, Man, and Cybernetics, Vol. 23, No. 5, pp. 1392-1398.
  8. Hespanha, J. P., Liberzon, D. and Morse, A. S., 2001, "Multiple Model Adaptive Control, Part 2: Switching," Int. Journal of Roboust Nonlinear Control, No. 11, pp. 479-496.
  9. Nam, K. H. and Song, J.-B., 2009, "Joint Torque Sensor Based on Hub-Spoke Type Structure for a Service Robot," Conf. on the KSME, pp. 247-249.