Fig. 1. Physical picture of the FSM

Fig. 2. Experimental platform

Fig. 3. Coupling model of the FSM

Fig. 4. Open-loop step responses (before decoupling)

Fig. 5. Block diagram of feedforward decoupling control system

Fig. 6. Open-loop step responses (after decoupling)

Fig. 7. Block diagram of composite sliding mode control structure

Fig. 8. The control voltage for different σ

Fig. 9. Response curves under decoupling and un-decoupling

Fig. 10. The estimated disturbance

Fig. 11. X-axis responses under external disturbance

Fig. 12. X-axis deflection angles

Fig. 13. 60 Hz circular trajectory tracking result

Fig. 14. 120 Hz circular trajectory tracking result