Fig. 1. Vibration model of PEM

Fig. 2. Dynamic heat exchange model of PEM

Fig. 3. Diagram of system light path

Fig. 4. J₄/J₂ varying with δ₀

Fig. 5. Duty cycle closed loop control system

Fig. 6. Flow chart of stability control system of PEM

Fig. 7. Test platform for stability control system of PEM

Fig. 8. Frequency sweep result

Fig. 9. Waveforms of driving square wave, driving voltage, and interference modulation signal, and relationship between duty cycle and driving voltage. (a) Waveforms of driving square wave, driving voltage, and interference modulation signal; (b) relationship between duty cycle and driving voltage

Fig. 10. Amplitude of phase modulation

Fig. 11. Phase modulation amplitude varying with time at 1/2 wave state, and PEM phase modulation without feedback. (a) Phase modulation amplitude varying with time; (b) PEM phase modulation without feedback

Fig. 12. Phase modulation amplitude varying with time at 1/4 wave state