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07 Nov 2002 GLW 1
MARS 2 Design Review-Optomechanical Review
MARS 2
Mechanical DesignReview
07 Nov 2002 GLW
2
MARS 2 Design Review-Optomechanical Review
Topics
• Drive axes– Orientation, location, &
travel range of axes– Typical axis drive
configuration– Axis loads, drives,
encoders, & bearings
• Optical mounts– Manual adjustments
• Beam splitter• Collimator• Lenslet/camera• Knife edge
• CCAS mounting• Current design status
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MARS 2 Design Review-Optomechanical Review
Drive Axes
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MARS 2 Design Review-Optomechanical Review
MARS 2 Remote AxesTop to bottom
• Wavescope camera• SenSys camera focus• Focus (Z)• X• Yaw (rotation about an axis parallel to Y)• Pitch (rotation about an axis parallel to X)• Y’ (combined with Focus to get Y)
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MARS 2 Design Review-Optomechanical Review
Axis Travel Ranges
AxisRequired Axis
Range Range source Axis Travel Motor/Actuator EncodingDesired
Resolution HomeLimits,
2X eachRemote operation
1 focus (z) +/- 25 mm
estimate based on current system,
thermal calculations, and comments 50 mm IMS rotary/absolute 0.001 mm x x
2 y' (used w/focus to get y) +/- 25 mmestimate, thermal
calcs 50 mm IMS rotary/absolute 0.001 mm x x3 x +/- 25 mm estimate/discussion 50 mm IMS rotary/absolute 0.001 mm x x4 pitch (about x or x') +/- 2 deg estimate/discussion +/- 20 mm IMS rotary/absolute 1 mRad x x5 yaw (about y) +/- 2 deg estimate/discussion +/- 16 mm IMS rotary/absolute 1 mRad x x6 camera 50 mm M Wolf doc, Dec 2001 50 mm IMS rotary/absolute 0.001 mm x x
7 knife edge voice coil range 0.30 in BEIvisual via camera,
switch x8 knife edge position (in/out) stage range 1.00 in Bimba in/out switches x9 HET shutter Bimba in/out switches x10 reference mirror shutter Bimba in/out switches x11 sensys camera focus estimate/discussion 1.0 in TS Products 0.001 mm x x
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MARS 2 Design Review-Optomechanical Review
MARS 2 Axes from Model
Y’
Pitch
Yaw
X
FocusCamera
SenSys
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MARS 2 Design Review-Optomechanical Review
Common Axis DriveComponents
• For all BUT the SenSys axis– Stepper motor– Ball screw with preloaded drive nut– Limit and home switches– Encoder (absolute, rotary)– Fail-safe brake (not on camera axis)
• SenSys camera axis– TS Products motor with internal encoder
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MARS 2 Design Review-Optomechanical Review
Axis Drive Resolution
• Stepper motor– 200 full steps per revolution– 10 msteps per full step
2,000 msteps per revolution
• Lead Screw– 2-mm per revolution lead screw– With mstepping results in 1 mm per mstep resolution
• will need ~1/2 mm per mstep for yaw and pitch resolution
• Absolute encoder– Parallel interface– Minimum encoder resolution of 2,000 counts per
revolution will count each mstep
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MARS 2 Design Review-Optomechanical Review
Axis Drive Loads
• Worst case is “uphill” motion• Loads consist of:
– Inertia load– Gravity component along axis– Friction
• Encoder• Bearings• Drive screw• Others
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MARS 2 Design Review-Optomechanical Review
Axis Loads
AxisLoad [lbf]
Torque [oz-in]
Camera 5.4 6.9
Focus 182 42.9
X 14.1 3.3
Yaw 38.8 9.2
Pitch 38.8 9.2
Y’ 19.0 4.5
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MARS 2 Design Review-Optomechanical Review
Linear Axis Mounting
• THK preloaded rails & bearings– Multiple rails with one block per rail– Slides mounted perpendicular to travel on one side will
prevent binding due to misalignment & thermally induced dimensional changes
• similar to bearing arrangement on the tracker carriage
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MARS 2 Design Review-Optomechanical Review
Yaw/Pitch Axis Mounting
• Yaw axis– THK radial cross roller bearing for the pivot– THK curved bearing rail for additional support
• similar to rho bearing on the carriage
• Pitch axis will use flex pivots for the pivot• Yaw and Pitch axes will use flex pivots and small
slides to accommodate (±2°) & L (~0.3 mm) at the drive nut
Lead screw
Stage
L
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MARS 2 Design Review-Optomechanical Review
Optical Mountsand Adjustments
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MARS 2 Design Review-Optomechanical Review
Optical Mounts
• Manual adjustments made with opposed adjusting screws where possible– Locks stage in position, does not rely on springs to
hold stage against adjustment screw
• Combination of flex pivots, pins, adjusting and clamping screws for yaw/pitch adjustments
• X-Y-Z and X-Z cross roller stages for translation
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MARS 2 Design Review-Optomechanical Review
Manual AdjustmentsPart 1
• Lenslet– x, y, yaw, pitch: aligns lenslet to optical axis
• Lenslet/camera stage– focus: positions lenslet/camera wrt collimator
• Collimator– x, y, yaw, pitch: aligns collimator to optical axis– focus: positions collimator wrt beam splitter cube
• Beam splitter cube– x, y, focus, yaw, pitch: aligns cube to laser beam
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MARS 2 Design Review-Optomechanical Review
Manual AdjustmentsPart 2
• Reference mirror– x, y, yaw, pitch: aligns mirror to optical axis– focus: positions mirror wrt HET focus
• SenSys camera– x, y: positions camera wrt optical axis
• Light source– x, y, focus: positions fiber wrt pin hole
• Knife edge– focus: positions knife edge wrt beam splitter cube
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MARS 2 Design Review-Optomechanical Review
Isometric View of MARS2Reference
Mirror
Beam splitter Cube
Collimator Lenslet
Knife Edge
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MARS 2 Design Review-Optomechanical Review
Mounting in CCAS Tower
• Remove everything down to 12-inch I-beams• Install stiffeners to forward cross beams• Install a layer of dampening material (plywood)• Install base plate
– Incorporates gross translation & tip/tilt adjustments
• Install base wedge with y’-axis• Install pitch, yaw, & x-axis assembly• Install assembled optical bench with focus axis• Install electronics rack
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MARS 2 Design Review-Optomechanical Review
CCAS Components
Frame stiffener
Dampening material
Base plate
12-inch I-beam
members
Electronics rack
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MARS 2 Design Review-Optomechanical Review
Current Design Status
• Most purchased components are identified• Final layout work & mounting details need to be
completed• Drive configuration needs to be finalized• Laser for component alignment needs to be
added• Drawing generation is the next big task
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MARS 2 Design Review-Optomechanical Review
Unknowns
• Tolerance analysis• Metal finishing-is it needed?
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MARS 2 Design Review-Optomechanical Review
Top View of MARS2
Camera Lenslet
ReferenceMirror
Knife Edge
Collimator Pellicle
Beam splitterCube
SenSys Camera
Light Source
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MARS 2 Design Review-Optomechanical Review
Relative Axis LocationsSide View
Y
Focus
Y’
Yaw
Pitch
Camera
SenSys
X
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MARS 2 Design Review-Optomechanical Review
Axis Drive Loadsin pictures and equations
W cos()W
a
Fdrive
Ffr
Note that: = 35° >> cos(35°) = 0.82gc = 386.4 in/sec2 >> for small a’s, cos() dominates
used a = 10 in/sec2 in calculationsNot all axes have a W cos() component
F = ma
Fdrive-Ffr-W*cos() = m*a
and with m = W/gc
Fdrive-Ffr-W*cos() = W*a/gc
Fdrive = Ffr + W*[cos() + a/gc]
rearranging
+
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MARS 2 Design Review-Optomechanical Review
Torque to Load
Ball screw with xx lead (pitch)
Motor
produces torqueDrive nut
converts torque to force
Drive coupling
= efficiency of ball screw, ~ 0.85-0.90
2 * *
Force * LeadTorque =
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MARS 2 Design Review-Optomechanical Review
Axis Drive Specifics• IMS stepper motor
– two sizes to cover six axes– dual shaft
• Schneeberger ball screw– 12-mm diameter for all but camera axis
• 3,400 N (770 lbf) static load s. f. min = 4.2• 2,500 N (565 lbf) dynamic load (L10) s. f. min = 3.1
– preloaded drive nut– special order for length and end configuration
• Absolute rotary encoder– parallel output– multi turn (25 turns needed)– 4,096 steps per revolution
• 2 encoder steps/1 mm• 1 encoder step /0.5 mm
• Electroid fail-safe brake– engages with power off
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MARS 2 Design Review-Optomechanical Review
Beam Splitter Mount
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MARS 2 Design Review-Optomechanical Review
Collimator Mount
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MARS 2 Design Review-Optomechanical Review
Lenslet/Camera Mount
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MARS 2 Design Review-Optomechanical Review
Knife Edge Mount