Fig. 1. Bonding position of strain gauge

Fig. 2. Structure of sensitive gates and Wheatstone full bridge circuit

Fig. 3. Remain ripples

Fig. 4. Process of sensor signal compensation

Fig. 5. Fourier series fitting results under different orders

Fig. 6. Effect of sensor signal compensation

Fig. 7. Frequency analysis of signal

Fig. 8. Contour map of strain simulation at the bottom of the flexspline

Fig. 9. Strain variation curve under different radius

Fig. 10. Apply glue on the bottom surface of the flexspline

Fig. 11. Prototype of the torque sensor

Fig. 12. Torque testing system

Fig. 13. Calibration curve

Fig. 14. Hysteresis curve

Fig. 15. Instantaneous excitation and step load

Fig. 16. Calibration curve of remain ripples

Fig. 17. Step loading test

Fig. 18. Sinusoidal variation loading test

Fig. 19. Collision during sinusoidal variation loading test