Fig. 1. Structure of dual-axis VCA-FSM

Fig. 2. Coupling model of dual-axis VCA-FSM

Fig. 3. Experimental platform of VCA-FSM servo control system

Fig. 4. Schematic diagram of VCA-FSM servo control system

Fig. 5. Technology method route of VCA-FSM system identification & model reduction

Fig. 6. Excitation signal & response signal curve

Fig. 7. Singular value of the Hankel matrix

Fig. 8. Singular value of system's balanced realization model

Fig. 9. Comparison curves of frequency characteristic of the model and the actual system before and after the reduction

Fig. 10. Structure diagram of dual-axis VCA-FSM sliding mode control system

Fig. 11. Closed-loop frequency characteristic curve

Fig. 12. Anti-disturbance amplitude-frequency characteristic curve

Fig. 13. Closed-loop step response curve

Fig. 14. Result of spiral signal tracking