1. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 MMT336 Characterization Software Armando Riccardi & Guido Brusa Presented by Armando Riccardi

2. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Outline Control loop description Feed-forward matrix measurement Flattening constrains Capacitive sensor calibration Conclusions

3. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Control loop Commands from WFC - + DM k-th Curr. Driver + coil Capsens Linearization @625Hz 40kHz local loop DSP of k-th channel -3dB@56kHz

4. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Control loop Commands from WFC - + DM k-th Curr. Driver + coil Capsens Linearization @625Hz 40kHz local loop DSP of k-th channel Limited DC gain of the loop (0.25 N/ m m) Compensation of the static error of the stiffer modes is needed

5. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Control loop Commands from WFC + + - + DM k-th Curr. Driver + coil Capsens Linearization @625Hz 40kHz local loop DSP of k-th channel Feed-forward

6. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 FF matrix measurement

7. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Modal measurement

8. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 The FF matrix fitting

9. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 FF matrix fitting

10. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001

11. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 FF matrix error propagation + + G - + K -1 K+eK+e dxdx

12. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 FF matrix error propagation

13. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Dangerous act. behavior

14. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Calibration of the cap-sens C meas C stray Ref. plate Thin shell Sensor board

15. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Calibration procedure Interferometer cannot sense the piston term Measurement of local tilt (relative measurements)

16. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Calibration of P30 cap-sens

17. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Closed loop operation Derivative error @ 40 m m: 0.9% Derivative variation in the range 30-50 m m:0.5% Robust closed loop operation if the interaction matrix is measured

18. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Open loop operation @50 m m Another procedure of calibration is needed: Gap-sensor (Steward Obs. - R. Johnston)

19. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Gap Sensors Gap sensor head Cold plate Fiber

20. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Gap Sensors Advantages: Faster calibration procedure Air turbulence doesn’t affect the measurement Adaptive secondary built-in devices Disadvantages: 24 gap sensors vs. 336 actuators: unsensed high order modes. Force calibration needed

21. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001

22. Osservatorio di Arcetri LBT AO Conceptual Design Review Steward Observatory - March 5-7, 2001 Conclusions Feed-forward matrix identification procedure is well established and fully working. High SNR and low (less 1%) propagation error coefficient just for high order modes. Calibration procedure for closed-loop operation has been already experimented on prototypes The calibration procedure will be tested for the MMT336 unit on the shimulator comparing gap-sensor and interferometer results