F. Barillot Cedrat Technologies MEFISTO Design & tests of a demonstrator for filet compensation mechanism

Transcription

1 F. Barillot Cedrat Technologies MEFISTO Design & tests of a demonstrator for filet compensation mechanism CEDRAT TECHNOLOGIES

2 Project goal Future matrix sensors will acquire an area on ground and are then susceptible to image shift due to satellite movement during acquisition. Design, Build and Test a breadboard mechanism that could shift telescope line of sight and freeze observed area during image acquisition. ESA Mechanism Final Presenation Days 2

3 Project organization RAPID project funded by French DGA Technical overview provided by CNES CTEC : SODERN : Project management Mechanism design and manufacturing GSE design and manufacturing Functional testing Vibration testing with CNES support Optical specification analysis Mirror design and manufacturing ESA Mechanism Final Presenation Days 3

4 CTEC space heritage with tilting mechanisms MEF Pharao (2006) BSM ATLID (2015) Mirror size Ø 4 mm Ø 27 mm Stroke 3 mrad x 3 mrad 3 mrad x 4.24 mrad Pointing stability 2 µrad over 20 days 0.5 µrad [1mHz 10 Hz] Temperature Regulated ~10mK 24 C 40 C, 1 K to 4 K drift Long term stability Not requested 50 µrad Repeatability Not requested 50 µrad ESA Mechanism Final Presenation Days 4

5 Single axis compensated mechanism Single axis tilt mechanism, partly funded through R&T CNES Compensation patented by CNES Stroke: 1 mrad, Response time : 3ms with1kg mirror ESA Mechanism Final Presenation Days 5

6 Requirements for the mirror (Sodern) Analysis of the optical requirements to define main performances of the mechanism and especially mirror. Mirror specification: o High opto-mechanical performances Mirroring surface (roughly 200 x 100) is part of requirement Very good flatness is required o Mechanical performances Mass < 1kg 1 st Eigen frequency > 1kHz o Assembly based on isostatic tripod ESA Mechanism Final Presenation Days 6

7 Design and Manufacturing of Mirror (Sodern) Mirror design successful o Mass = 745g o 1 st Eigen mode = 1088 Hz Material is Aluminum but study includes SiCand ZeroDur Mirror built by Sodernfor assembly in MEFISTO mechanism ESA Mechanism Final Presenation Days 7

8 Amplified Actuator Mechanism 2 x 8 APA120ML piezoelectric amplified actuators which offer a reinforced variant for space applications Total moving mass 2Kg Mirror & Support Available stroke o 80 µm o 1.5 mrad Hot redundancy APA120ML Piezo actuators Baseplate Counter mass is balanced to match Mass, Cog and moments of inertia. Countermass ESA Mechanism Final Presenation Days 8

9 Amplified Actuator Mechanism Simulation results o 1 st mode 700Hz (without support plate) Shocks ( 250g SRC) and Random (15g RMS) capability compliant with ECSS using reinforced APA120ML-PP ESA Mechanism Final Presenation Days 9

10 Mechanism demonstrator ESA Mechanism Final Presenation Days 10

11 Switching Amplifier Energy recovery Current limitation SA 75 Electronic driver Protected vs. over-current & over-voltage ESA Mechanism Final Presenation Days 11

12 SA75 Driver properties Data Values Output Voltage 170Vppk Output current Max 20Apk continuous Input Voltage 110VAC-263VAC Expected input power <75W Efficiency (max power) ~93% Voltage Bandwidth (-3dB) 1.3kHz Current Bandwidth (-3dB) Min 5kHz Output Control Voltage or Current ESA Mechanism Final Presenation Days 12

13 Position sensor - Probe Eddy current sensor: Impedance measurement allows monitoring position =, +, Probe Target size ESA Mechanism Final Presenation Days 13

14 Position sensor Conditionning electronic ECS75-2 standard sensor conditioning electronic Fixed frequency measurement Integrated polynomial correction PERFORMANCES ATTENDUES Measurement range Linearity Resolution Short term (1cycle) repeatability Long term stability (3 month) Thermal requirement Sampling rate VALEURS µm +/-1% stroke or +/-800nm < 10nm +/-200nm +/-600nm +/-0.5 C >100kSamples/s ESA Mechanism Final Presenation Days 14

15 Control strategy: Base principle of the control loop o Ensure that following error is small and as stable as possible during the integration (Ti). o Linearisethe piezoelectric actuators response using local sensor o Counter reacted closed loop Position Mirror Collocalised position sensor External command from system control (mirror control) Control loop for One actuator Piezo actuator Ti Time ESA Mechanism Final Presenation Days 15

16 Injected profile definition Purpose: Shape the command signal to achieve the expected speed position/speed command while avoiding discontinuities. Reduce oscillations and rejected µvib in the overall structure 5 x 10-5 Preshaper Retournement preshaper consign Stroke (m) speed (meter per second) time (s) Accélération time (second) Accélération nulle Vitesse constante Déaccélération Déaccélération Accélération ESA Mechanism Final Presenation Days 16

17 Control law design Single mode foot model Preliminary study based on Fr 800Hz foot resonant mode assumption 25 / 50 µmuseful displacement, Ti = 1ms Without preshaping With preshaping 6 x 10-5 consign versus actuator position 6 x 10-5 consign versus actuator position stroke (m meter) (meter) stroke ( time (second) 7 x 10-6 Residual error time (second) 4 x 10-7 Residual error error (meter) error (meter) time (second) Residual error: ~1.5µm time (second) Residual error: ~500nm over Ti, ~100nm over Ti/2 ESA Mechanism Final Presenation Days 17

18 Mechanism dynamic model Multiple inputs / outputs / modes Dynamic model of the complete mechanism is built in MATLAB/Simulink Based on Finite Element Model Piezoelectric components electromechanical conversion is included ESA Mechanism Final Presenation Days 18

19 Electrical architecture UC65 Digital Controller Foot 1 Foot 2 ECS75 Sensor conditioning Foot 1 Foot 2 Sensor Foot 1 Sensor Foot 2 DAQ Board National Instrument NI6259 AC-DC HV AC-DC HV SA75 Driver Foot 1 Foot 2 SA75 Driver Foot 3 Foot 4 MECANISM Foot 1 MECANISM Foot 3 MECANISM Foot 2 MECANISM Foot 4 Sensor Foot 3 Sensor Foot 4 UC65 Digital Controller Foot 3 Foot 4 ECS75 Sensor conditioning Foot 3 Foot 4 ESA Mechanism Final Presenation Days 19

20 Overview of test bench Digital Controller & Sensors Actuators drivers Amplified Piezo Actuators APA120ML Counter Mass ECS Sensor Miror & supports ESA Mechanism Final Presenation Days 20

21 Control loop test results Amplitude (µm) Amplitude (µm) Feet excitation Time (s) Time (s) Feet 1 & 2 Displacement Order12(µm) Order34(µm) Tension - Tensionpieds12 Tension - Tensionpieds34 Sensor1 (µm) Sensor2(µm) Order12(µm) Error 12 (µm) Amplitude (m/s) E E E E E E E E Amplitude (µm) Time (s) ESA Mechanism Final Presenation Days Feet1 & 2 speed E E E+01 Feet 1 & 2 Error Time (s) Speed consign12 average Speed sensor1 average Error 12 (µm) 21

22 Rejected vibrations measurement Measurement done in Toulouse at CNES CST facilities with CNES funding. Operating mechanism with and without countermass and measure rejected forces & moments ESA Mechanism Final Presenation Days 22

23 Verification of countermass influence Various cycle speed tested Result o Negative influence for X and MX due to CoGoffset o Significant improvement for Z, MY ESA Mechanism Final Presenation Days 23

24 Conclusion MEFISTO mechanism designed, built and tested. o It provides 1.5 mrad/ 80µm displacement capability. o Using reinforced actuators, it can survive launch shocks and vibrations o Fast moving capability for 0.75 kg mirror is demonstrated A complete closed loop test bench has been built o Simulation capability has been demonstrated o Control law have been tested to verify filet compensation capability The rejected forces & moments have been measured The MEFISTO project has allowed us to go through all the key aspects for a fillet compensating mechanism. The lessons will be valuable addition for future design of similar mechanisms. We would like to acknowledge CNES and French DGA for their continuing support in this project. ESA Mechanism Final Presenation Days 24