Hydraulic Actuators for the LIGO Seismic Retrofit

Transcription

1 Hydraulic Actuators for the LIGO Seismic Retrofit Stanford, Caltech, LSU, MIT, LLO Rich Abbott, Graham Allen, Daniel DeBra, Dennis Coyne, Jeremy Faludi, Amit Ganguli, Joe Giaime, Marcel Hammond, Corwin Hardham, Wensheng Hua, Jonathan Kern, Brian Lantz, Ken Mailand, Ken Mason, Rich Mittleman, Jamie Nichol, Joshua Phinney, David Shoemaker, Michael Smith LIGO Seismic Retrofit DRR, April 2002, BTL 1

2 Outline Placement of Sensors and Actuators in the system. Description of Actuator. - Mechanical Configuration. (Housing, Offload springs, sensor location) - Laminar flow hydraulic bridge. Performance considerations. - Range, velocity and bandwidth. - Noise performance. Sensors and ground motion. (already covered by Joe) Fluid supply noise and cross-regulation noise. Sample isolation at Stanford. Test Plan LIGO Seismic Retrofit DRR, April 2002, BTL 2

3 Placement of an External Isolation System Replace the coarse and fine actuators. Isolate the stack input in all 6 DOF. BSC HAM LIGO Seismic Retrofit DRR, April 2002, BTL 3

4 payload offload springs (2) tangential actuator Placement of the Actuators and Offload Springs vertical actuator Existing 4-layer passive stack DIT-5200 displac (Hydraulic L-4C geophone All the pier-top components are mounted into a frame Frame holds: 1 vertical and 1 tangential actuator, (isolation and alignment in 6 DOF) Pair of offload springs and initial alignment fixtures Sensors which are not included in the actuators STS-2 b LIGO Seismic Retrofit DRR, April 2002, BTL 4

5 1 pump 3 Hydraulic Actuator Basics 2 3 (1) Pump supplies a constant flow of fluid to the actuator. (2) Fluid flows continuously through a hydraulic Wheatstone bridge. (3) By controlling the resistance, one generates differential pressure across the bridge, which are connected to (4) Differential bellows which act as a stictionfree piston. (5) The actuator plate is between the bellows, and is connected to the payload with a flexure stiff in 1 DOF Laminar flow high viscosity (100x water), low velocity (80 microns/ sec.), fluid path geometry. Motion with flexures Offload springs to keep bridge balanced common mode rejection of pump noise LIGO Seismic Retrofit DRR, April 2002, BTL 5

6 Hydraulic Valve forms the bridge Differential bridge in a single valve body 4 nozzles one for each resistor in the bridge Original nozzles replaced with custom units shown below right. Flow in the DYP-2S Parker DYP-2S valve The new nozzle Ps nozzle C1 C2 flapper torquer motor Pr DYP-2S valve original new LIGO Seismic Retrofit DRR, April 2002, BTL 6

7 Drawings of the Actuator Payload attachement point Connection tripod Bellows enclosed with protective shields L-4C connector L-4C Bellows Actuator Plate Actuator Plate Valve Isometric view left shows major components Cross section above shows buried L-4C geophone LIGO Seismic Retrofit DRR, April 2002, BTL 7

8 The Test Platform at Stanford Bellows (within shield) Actuator plate Valve (not visible) Sensor platform Tripod flexure Vertical Actuator version 2 Horizontal Actuator Vertical Actuator (version 1) Witness Seismometer (Geotech S-13) Seismometer (STS-2) Offload Springs 800 lb Test Mass LIGO Seismic Retrofit DRR, April 2002, BTL 8

9 Test Platform Dynamics Valve to Displacement Sensor With Bypass Without 10 0 Mag Valve drive -> Payload displacement System acts like an integrator until: offload spring balances pressure difference (30 mhz) payload resonance against bellows spring (23- ~40 Hz) hertz 0 degrees hertz LIGO Seismic Retrofit DRR, April 2002, BTL 9

10 Bypass Network 2 1 Flow restric tor Diaph ragm Actuator plate pump 5 LIGO Seismic Retrofit DRR, April 2002, BTL 10

11 Performance Measures Bandwidth = Hz, mass/ spring resonance of actuator against the payload. Max range = +/- 1 mm, to accommodate long term locking, set by bellows geometry. Velocity = 80 microns/sec, well beyond typical peak velocity, set by bellows area and bridge flow. Three dominant noise sources: Ground motion coupling (limited by loop gain, sensor matching, low frequency tilt) Sensor noise (limited by cost, dynamic range, space) Pump noise (limited by line dynamics, acceptable power loss to filtering) LIGO Seismic Retrofit DRR, April 2002, BTL 11

12 Distribution Network Pump station provides source of quiet fluid for 2 vacuum chambers. Pump pressure fluctuations couple to drive force when the hydraulic bridge is unbalanced (lose common mode rejection.) Pump fluctuations are controlled both actively and passively. Accumulators at the distribution manifold attenuate the cross-modulation amongst actuators cross regulation accumulators (1 supply, 1 return) distribution manifold 1 pair in 8 pairs out Chamber 1 Existing 4-layer passive stack Hydraulic Actuator STS-2 Existing 4-layer passive stack motor controller pump stand controller external pressure input tach motor pump active control man. passive control man. distribution lines up to ~ 60 meters Hydraulic Actuator reservoir Pump Station Chamber 2 STS-2 LIGO Seismic Retrofit DRR, April 2002, BTL 12

13 Allowed Pump Noise Allowed pressure fluctuations, actuator servos on, 70 psi nominal, 0.25 pressure recovery e e3 pressure fluct, psi/rthz Allowed pump fluctuation pump noise goal 6.9e2 6.9e1 6.9e0 6.9e-1 pressure fluct, Pa/rtHz 10-5 Stanford pump noise * Predicted transmission 6.9e e freq Hz final_allowed_noise_5w_noise.fig March LIGO Seismic Retrofit DRR, April 2002, BTL 13

14 Performance of the Test Stand geophone v m Compensator displacement z m -z g + + z g STS2 Filter External Alignment Input LIGO Seismic Retrofit DRR, April 2002, BTL 14

15 Vertical Isolation Absolute Motion of Mass and Ground motion [m/ Hz] freq [Hz] 10 1 Vertical Transmission of ground motion with Sensor Correction ground mass Magnitude SC gain = Super Sensor Loop Gain = -1.0 Vertical Super Sensor Controller: v hyd cont freq [Hz] 10 1 passive active LIGO Seismic Retrofit DRR, April 2002, BTL 15

16 Test Plan There are 3 versions of the actuator: version 1 welded design, testing complete version 2 bolted design, testing underway at Stanford version 3 welded design, for use in LASTI, design almost complete Major Test Areas Characterize the version 2 actuator at Stanford and new valve at Stanford. Prove pump station noise at Caltech. Build and test all the interface and control electronics Use LASTI to practice installation and cleanliness techniques Install the system at LASTI Conduct real Sys-ID Isolated and Align 6 DOF with 8 Actuators Integrate with LDAS LIGO Seismic Retrofit DRR, April 2002, BTL 16

17 That s all, folks! Extra Slides LIGO Seismic Retrofit DRR, April 2002, BTL 17

18 Time Line April 12: Preliminary design review Next stage: Testing in LASTI 2 DOF, simple structure -> 6 DOF, dynamic payload (tests continue at Stanford & Caltech) April: Design of LASTI actuator and frame finalized parts start arriving May: housing arrive June: Sensors, actuators, fixturing arrive at LASTI July: Springs arrive Aug-Sept: Assemble system Oct: Begin LASTI system tests LIGO Seismic Retrofit DRR, April 2002, BTL 18

19 Pipeline dynamics impact filtering LIGO hydraulic-filter transimpedance magnitude pbridge/qpump (Pa-sec/m 3 ) v = 1000 m/s L ~ 60 m f ~ 4 Hz no passive stages one passive stage frequency (Hz) LIGO Seismic Retrofit DRR, April 2002, BTL 19

20 Mass 2 m. d z p 2 p. 1 A k. z z g D d t 2 Volumes d t p. 1 d V β d t p. 2 d V β Flow p s p 1 R p s p 2 Valve R 1 R 2 R R 1 Cv. i R 1 Cv. i Q 1 A. d z d t Q 2 A. d z d t Equations of Motion d t z g d d t z g d Q 1 p 1 p R R 1 0 Q 2 p 2 p R R 2 0 LIGO Seismic Retrofit DRR, April 2002, BTL 20

21 Conditioning a Pressure Source Active and Passive Suppression of Pressure Fluctuations Pressure Sensor Compensator Accumulator Pump Servo Valve Reservoir LIGO Seismic Retrofit DRR, April 2002, BTL 21

22 Pressure Noise at the Actuator no accumulator with accumulator accumulator and servo control pressure ASD (psi/ Hz) Freq (Hz) LIGO Seismic Retrofit DRR, April 2002, BTL 22

23 Horizontal Isolation Transmission Between S13 horz and sts-2 on 14-May Magnitude 10-1 control off control on freq [hz] LIGO Seismic Retrofit DRR, April 2002, BTL 23

24 More complete servo diagram environment sensor noise n d (ω) + + environmental disturbance d(ω) command input r(ω) y (ω) m + measured environment feedback controller K(s) M(s) sensor correction K (s) ff n (ω) f feed-forward controller force actuation actuator noise other measurements system dynamics G(s) G (s) + + d measured motion + "real" output y(ω) motion + n (ω) s sensor noise LIGO Seismic Retrofit DRR, April 2002, BTL 24