Fig. 1. Experimental platform

Fig. 2. Pseudo-random and Sinusoidal signal response

Fig. 3. Frequency response of the system obtained by combination

Fig. 4. System frequency response and fitting curves

Fig. 5. System uncertainty

Fig. 6. Fitting curves of friction torque

Fig. 7. Block diagram of friction compensation algorithm

Fig. 8. Frictionless compensation tracking curve

Fig. 9. Friction compensation tracking curve

Fig. 10. Tracking error comparison

Fig. 11. Multi-objective complementary control framework

Fig. 12. Mixed-sensitivity control structure

Fig. 13. Robust stability condition

Fig. 14. Multi-objective complementary control

Fig. 15. DOB control block diagram

Fig. 16. Stability conditions of closed-loop systems

Fig. 17. Comparison of disturbance attenuating performances

Fig. 18. Control principle diagram

Fig. 19. Step response

Fig. 20. Trajectory tracking control with 0.1 Hz

Fig. 21. Trajectory tracking error with 0.1 Hz

Fig. 22. 0.5 Hz tracking of the perturbed system model

Fig. 23. Comparison of disturbance rejection

Fig. 24. Disturbance suppression with 2 Hz

Fig. 25. Disturbance suppression with 5 Hz