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CELT Mirror Actuator Survey

CELT Mirror Actuator Survey. Presented by: J. Alan Schier The Pilot Group March 8, 2001. Requirements Filter No. 1. We want about 4000 actuators with: 1.2 mm stroke 4 nm resolution Cost < $2k each. This is a decent first pass filter. There are still finer filters.

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CELT Mirror Actuator Survey

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  1. CELT Mirror Actuator Survey Presented by: J. Alan Schier The Pilot Group March 8, 2001

  2. Requirements Filter No. 1 We want about 4000 actuators with: • 1.2 mm stroke • 4 nm resolution • Cost < $2k each This is a decent first pass filter. There are still finer filters...

  3. Requirements Filter No. 2 • Incremental Accuracy: • 4 nm • 10% of step • Tracking Rates: 0 to 170 nm/sec • Tracking Accuracy: <7 nm RMS • Slew Rate: >10 m/sec • Axial Stiffness: >10 N/m • Axial Load: >300 N Whichever of the two is larger for a given incremental move. For f’s above mirror loop bandwidth 100 Hz resonance with nominal mirror load

  4. Requirements Filter No. 3 Still important but seem easier to engineer: • Command Rate: >10 Hz • Transverse Load: > 5 N • Transverse Stiffness: >0.1 N/m • Operating Temperature: 2 8 C • Survival Temperature: 5 25 C There are yet a few more criteria...

  5. Additional Criteria • Environmental Suitability: • Humidity: 0 to Condensing • Low EMI Generation • EMI Immunity: Arc Welder at 6(?) Feet, etc. • Immune to Dust, Grit, Falling Wrenches… • Installation/Servicing: • Easy • Fast

  6. Lifetime & Reliability Failure rate no worse than 1:2000 per year for at least 10 years.

  7. Lifetime/Reliability Uncertainties Doubt about usual life/reliability calc’s. • Rolling Elements  Surface Fatigue • Sliding Elements  Abrasive Wear • Both count on lubrication. • Both count on motions larger than particle size. “Micro-welding” likely an issue

  8. Keck Roller Screw Life Calc Just For Fun: Calculate a few Keck roller screw surface fatigue numbers. • 1% fail in 330 years. • 10% fail in 1700 years. • Failure rate at 10 years: 10-4/year. • Failure rate of 10-3/year at 55 years.

  9. Candidate Actuator Summary • Motorized Micrometer and Lever • High Resolution Micrometer • Elastic Leverwith Encoded Input • Voice Coil • Inchworm and Lever • High-Capacity Inchworm

  10. Motorized Micrometer and Lever Proposed by CSEM (Dr. Lorenzo Zago)

  11. Motorized Micrometer and Lever • Proposed with Physik Instrumente Motorized Micrometer. • Two Flexured Lever Options. • $75k Development for First Prototype (verbal per Zago). • Micrometer Life?

  12. Physik Instrumente Micrometer • M-230 High Resolution Closed-Loop DC-Mike Actuators • 10 & 25 mm Travel Range • 0.05 µm Minimum Incremental Motion • Non Rotating Tip • Velocity to 1.5 mm/sec. • Closed-Loop DC Motor • Integrated Hall-Effect Limit Switches • Front Mount or Clamp Mount

  13. High Resolution Micrometer • High Resolution Micrometer Proposed by Diamond Motion (Formerly TS Products) • Provided HET Segment Actuators

  14. High Resolution Micrometer Provided by Diamond Motion

  15. High Resolution Micrometer • Motor/Gearhead/40-Pitch Screw. • 2.5 nm theoretical resolution. • Zero-backlashgearhead (Micro-Mo). • Stepper Driven • Power an issue • Could be DC motor driven. • Life? Reliability? Backlash?

  16. High Resolution Micrometer • <$2k each for prototypes • 5-week delivery. • $750 each in volume (verbal estimate)

  17. Elastic Lever Proposed by TPG after A.E. Hatheway Output Location Motor/Cable Drive Encoder Mounting Surface

  18. Elastic Lever • 35:1 reduction as shown. • Axial stiffness provided by output beam. • Weight <6 lbs. • Gearhead and Motor Life?

  19. Elastic Lever • $18,800 for Prototype Ready to Test • 12-Week Delivery • Small Quantities <$2k Each

  20. Voice Coil Proposed by Blue Line Engineering

  21. Voice Coil • Minimal Life Issues • No rolling or sliding elements • Electronics tractable in advance • High-Frequency Vibration Isolation • Possible Active Damping In-Band • Hinges On Sensor Performance

  22. Voice Coil Sensor 1.5cm Coil Demo System: Offset 500um Range +/-600um Target Any (Al used) Resolution <0.18nm RMS/√Hz Short Term Stability <0.97nm RMS Long Term Stability TBD nm RMS Overall Accuracy TBD um Data Provided by Blue Line Engineering

  23. Voice Coil • $35k to Deliver Prototype • 5 Month Development Effort

  24. Inchworm/Lever • Proposed by Etrema Products • Would Use Magnetostrictive Material

  25. Inchworm/Lever • Proposed with 9:1 Lever System • Reduces force on brake • Reduces “glitch” when clamping • Will Likely Need an Output Sensor

  26. Inchworm/Lever • Etrema Proposes Development Effort • Design and build in two stages • $112k total • 5 month duration

  27. High Capacity Inchworm • Developed by Dr. Greg Carman, UCLA • Exists As Lab Device

  28. High Capacity Inchworm

  29. High Capacity Inchworm Existing Device: • 500 N capacity • 3 mm stroke • 11 m groove spacing • Demonstrated to 109 full steps

  30. High Capacity Inchworm • Must Align Grooves When Clamping • Need Some Way to Know Alignment With Changing Load • May Need a Sensor • But it is only necessary to sense the spine extension or groove alignment

  31. High Capacity Inchworm • Estimated $50k for CELT Redesign • Interested in Working With Manufacturer

  32. What Else Has Been Investigated? Keck Actuators: • High Cost • ≈$10k each • Roller Screws $1.5k each • Reliability appears manageable • Screws don’t fail • Cleanliness • Lubrication (oil with antisieze) • But hydraulic reducers leak

  33. What Else Has Been Investigated? Non-Responders: • Ball Aerospace • IDC Motion Control (Issued Formal No-Bid) • SKF/Exlar/Moog (Roller Screws)

  34. What Else Has Been Investigated? Burleigh • Catalog inchworm has 15 N capacity • NGST inchworm has 5 N capacity • $200-$300k (?) for development effort

  35. What Else Has Been Investigated? Direct Piezoelectric/Magnetostrictive: • >3 kg of material required • >1 mlength of active material • >$3000 for magnetostrictive element • Daunting complexity for piezoelectrics • But...Piezoelectric May Still Be Feasible If A Manufacturer Were Interested.

  36. What Else Has Been Investigated? • Differential Screws/Differential Ball Screws • Uncertain Life Issues • Ball Screw Cost ≈$1.2k in Volume (Steinmeyer) • May Be Feasible If Life/Reliability As In Keck • Benefit From Output Sensor

  37. What Else Has Been Investigated? • Motorized Micrometers • Initially set aside due to life and cost • Cost ≈$1300-$1500 in small quantities • Need a lever • Life of screw an uncertain issue • Now proposed by CSEM and Diamond Prod. • Life Still Unresolved • Benefit From Output Sensor

  38. What Else Has Been Investigated? • JPL Optical Delay Line • Piezoelectrics on voice coil • Unnecessary complexity • Rolvis Roller Screws • Cost ≈$1200 in volume

  39. What Else Has Been Investigated? New Focus Pico Motor • Slew rate limited • Needs output sensor as motion is load/friction dependent

  40. What Else Has Been Investigated? Steward ObservatoryImpulse Screw • Slew rate limited • Needs output sensor as motion is load/friction dependent.

  41. What Else Has Been Investigated? Two Stage Actuators • Initially set aside because of need for output sensor • Viable With Output Sensor: • Small (10 m stroke?) piezoelectric stack • Rolled ball screw <$150 in singles

  42. What Else Has Been Investigated? Thermal Actuators • Nitinol • Thermally reversible strain of about 3% • Can deliver about 1 joule/gram • Paraffin Wax • 15% volume increase from solid to liquid • Can deliver about 10 joule/gram • Energy Dense • Same range as electromagnetic (wax is higher) • 1-2 order of magnitude higher than PZT • How To Get The Heat Out Fast Enough?

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