Fig. 1. Schematic of 8-m-RST primary mirror system. (a) Top view; (b) sensor, controller and actuator; (c) segmented mirror, support system, actuator and truss

Fig. 2. Finite element model of 8-m-RST

Fig. 3. Schematic of pulsed wind speed field

Fig. 4. Two unobservable control modes of primary mirror system. (a) Focus mode; (b) global axial translation mode

Fig. 5. Schematic of synchronous sampling for edge and tilt sensors

Fig. 6. Modeling chart of primary mirror and its control system

Fig. 7. Bode diagram of open-loop system. (a) Input: mode 1, output: mode 1 and mode 2; (b) 72 modes

Fig. 8. Two most sensitive control modes of primary mirror system in 8-m-RST. (a) Mode 1; (b) mode 2

Fig. 9. Bode diagram of system. (a) Continuous time system; (b) discrete time system; (c) Bode diagrams of open-loop and closed-loop systems for mode 1

Fig. 10. Step response for mode 1

Fig. 11. Nichols chart of unity gain system. (a) Continuous time system; (b) discrete time system (sampling period is 0.1 s)

Fig. 12. Nichols charts of system when relative stablity requirment is satisfied. (a) Continuious time system, integral gain of 3.3; (b) samping time of 0.05 s, integral gain of 2.0; (c) samping time of 0.1 s,integral gain of 1.3; (d) samping time of 0.2 s, integral gain of 0.71

Fig. 13. Spectrum of pulsed wind speed field

Fig. 14. Bode diagram of disturbance input for primary mirror control system. (a) Open-loop state; (b) closed-loop state

Fig. 15. Step response of disturbance input for mode 1 as example

Fig. 16. Error signals under wind disturbance. (a) Error of Mode 1; (b) error of mode 67; (c) error of actuator; (d) RMSE of actuators

Fig. 17. Mode 67

Fig. 18. Power spectra of error signals under wind disturbance. (a) Mode 1; (b) mode 67; (c) actuator; (d) RMSE