Hydraulic External Pre-Isolator Rich Abbott, Graham Allen, Drew - PowerPoint PPT Presentation

Hydraulic External Pre-Isolator Rich Abbott, Graham Allen, Drew Baglino, Colin Campbell, Daniel Rich Abbott, Graham Allen, Drew Baglino, Colin Campbell, Daniel DeBra, Dennis Coyne, Jeremy Faludi, Peter Fritschel, Amit Ganguli, i, DeBra, Dennis Coyne, Jeremy Faludi, Peter Fritschel, Amit Gangul Joe Giaime, Marcel Hammond, Corwin Hardham, Gregg Harry, Joe Giaime, Marcel Hammond, Corwin Hardham, Gregg Harry, Wensheng Hua, Jonathan Kern, Brian Lantz, Wensheng Hua, Jonathan Kern, Brian Lantz, Ken Mailand, Ken Mason, Rich Mittleman, Jamie Nichol, Ken Mailand, Ken Mason, Rich Mittleman, Jamie Nichol, David Ottaway Ottaway, Joshua Phinney, Norna Robertson, Ray Scheffler, , Joshua Phinney, Norna Robertson, Ray Scheffler, David David Shoemaker, Mike Zucker, and the Livingston Staff David Shoemaker, Mike Zucker, and the Livingston Staff 1 LIGO-G030227-00-R B Lantz, EPI review, April 03

Outline Why choose hydraulics? How the actuator works Pump Station Sensor Blending Control loop shaping Performance 2 LIGO-G030227-00-R B Lantz, EPI review, April 03

Benefits of Hydraulics Heating: Actuator dissipates 10W and heat is carried away by the working fluid. Range: +/- 1 mm gives headroom for seasonal drift, small earthquakes, tilts of the floor. Response to saturation: Good recovery from saturation, simple loops and max velocity of 80 microns/ sec make recovery smooth. Damping of the elastic behavior of the stack – it’s like having a dashpot at the tip of the crossbeam. Stiffness gives large rejection of stack dynamics, makes control easy. 3 LIGO-G030227-00-R B Lantz, EPI review, April 03

Candidate Actuators Displacement Mechanical Hysteresis Stiffness n y o t i i Force c t Noise c o i l t e S V Hydraulic High Low Med Med Low Low Low Ball Screw High Low High High High Low High Linear Motor Med High Low High Low Low Low Piezo or High High High Low Low High Low Magnetostriction 4 LIGO-G030227-00-R B Lantz, EPI review, April 03

Hydraulic Actuator Basics (1) Pump supplies a constant flow of fluid to the actuator. (2) Fluid flows continuously through a hydraulic Wheatstone bridge. 2 (3) By controlling the resistance, one generates differential pressure across the bridge, 1 which are connected to pump (4) Differential bellows which act as a stiction- free piston. (5) The actuator plate is between the bellows, 3 3 and is connected to the payload with a flexure stiff in 1 DOF • Laminar flow 4 4 high viscosity (100 x water), low velocity (80 microns/ sec.), 5 fluid path geometry. • Motion with flexures • Offload springs to keep bridge balanced common mode rejection of pump noise 5 LIGO-G030227-00-R B Lantz, EPI review, April 03

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. Parker DYP-2S valve The new nozzle Flow in the DYP-2S Ps nozzle torquer C1 C2 e r p p f l a motor Pr original new DYP-2S valve 6 LIGO-G030227-00-R B Lantz, EPI review, April 03

Bypass Network 2 1 pump Flow restrictor Actuator plate 3 3 D i a p h r a g m 4 4 5 7 LIGO-G030227-00-R B Lantz, EPI review, April 03

The Test Platform at Stanford Vertical Actuator (version 1) Bellows (within shield) Witness Actuator Seismometer plate (Geotech S-13) Valve Seismometer (not visible) (STS-2) Sensor Offload platform Springs Tripod flexure 800 lb Test Mass Horizontal Actuator Vertical Actuator –version 2 8 LIGO-G030227-00-R B Lantz, EPI review, April 03

Test Platform Dynamics Valve to Displacement Sensor With Bypass Without 0 10 Mag -2 10 Valve drive -> Payload displacement System acts like an integrator until: offload spring balances pressure difference (30 mHz) -1 0 1 2 10 10 10 10 hertz payload resonance against bellows spring (23- ~40 Hz) 0 degrees -200 -400 -600 -1 0 1 2 10 10 10 10 hertz 9 LIGO-G030227-00-R B Lantz, EPI review, April 03

Drawings of the Actuator Payload attachement point Connection tripod L-4C connector L-4C Bellows Actuator Plate Bellows enclosed with protective shields Actuator Plate Isometric view left shows major components Valve Cross section above shows buried L-4C geophone 10 LIGO-G030227-00-R B Lantz, EPI review, April 03

Distribution Existing 4-layer passive stack Network Hydraulic Actuator accumulator external pressure input motor pump stand controller controller tach motor STS-2 Existing 4-layer passive stack pump reservoir Pump Station Hydraulic Actuator 60 meter supply and return accumulator STS-2 11 LIGO-G030227-00-R B Lantz, EPI review, April 03

Allowed Pump Noise Allowed pressure fluctuations, actuator servos on, 70 psi nominal, 0.25 pressure recovery 0 10 -1 10 pressure fluct, psi/rtHz maximum allowed pump noise maximum allowed pump noise maximum allowed pump noise maximum allowed pump noise -2 10 -3 10 pump noise goal pump noise goal pump noise goal pump noise goal -4 10 measured pump * calculated impedance measured pump * calculated impedance measured pump * calculated impedance measured pump * calculated impedance -5 10 -6 10 -1 0 1 2 10 10 10 10 freq (Hz) final_allowed_noise_btl4.fig 12 LIGO-G030227-00-R B Lantz, EPI review, April 03

Extra slide – pump noise Pressure Noise at the Distribution Manifold -2 10 pressure ASD (psi/rtHz) requirement -3 10 -4 10 -1 0 1 2 10 10 freq (Hz) 10 10 13 LIGO-G030227-00-R B Lantz, EPI review, April 03

Placement of an External Isolation System •Install an isolation and alignment system without opening the chambers. •Replace the coarse and fine actuators which are currently between the pier BSC and the cross beam weldment (which hold the support tubes and support table) •New system will act to hold support table still in the presence of ground motion HAM 14 LIGO-G030227-00-R B Lantz, EPI review, April 03

offload springs (2) Placement of the payload Actuators and tangential actuator 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 15 LIGO-G030227-00-R B Lantz, EPI review, April 03

How to maintain Alignment, and have Isolation from the Ground payload Geo offload spring supports payload displacement sensor Simple model for 1 DOF has: •Payload to be isolated from the •Ground •Offload springs to support the load and set the static alignment STS-2 •Feedback displacement sensor ground •Feedback inertial sensor •Actuator •Translational DOFs have ground motion sensors 16 LIGO-G030227-00-R B Lantz, EPI review, April 03

How to maintain Alignment, and have Isolation from the Ground payload geo disp Geo K offload spring supports payload blend displacement sensor To make a control loop: •Blend displacement and inertial sensors (super sensor) •Add control, drive actuator STS-2 •Below blend freq it’s a positioning ground system (command alignment to DC) •Above blend freq it’s an isolation system from ground motion •Always resists external payload forces 17 LIGO-G030227-00-R B Lantz, EPI review, April 03

How to maintain Alignment, and have Isolation from the Ground payload geo disp Geo K 2 - S T S offload spring supports payload blend and correct displacement sensor Sensor correction extends isolation: •Low freq control with disp. sensor has typical benefits – improved linearity, hysteresis, since our sensors are better STS-2 than our actuators ground •Replace low freq crossover with blend •To achieve isolation, feed information from STS-2 to correct the displacement sensor. 18 LIGO-G030227-00-R B Lantz, EPI review, April 03

Implementation in 6 DOF • Piers at the four corners can be used for 6 DOF system with vertical and tangential actuators, sensors, and offload springs. • Offload springs form a V to give better load handling. • At low frequencies, translations are different than rotations because (based on PEPI results) slab translations cause more problems that slab rotations. • At low freq (microseism to a few Hz) isolate against translations, and actively lock payload rotations to slab rotations. 19 LIGO-G030227-00-R B Lantz, EPI review, April 03

Implementation in 6 DOF Piers support the payload (blue) EPI system frame (purple) atop the pier EPI controls the support table (green) Stack (not shown) sits on the support table 20 LIGO-G030227-00-R B Lantz, EPI review, April 03

Hydraulic Crossbeam Offload Horizontal Springs Installation Actuator fun! Hydraulic lines & valves Pump Station Hydraulic Lines 21 LIGO-G030227-00-R B Lantz, EPI review, April 03