mars 2 design review-optomechanical review 07 nov 2002 glw1 mars 2 mechanical design review

07 Nov 2002 GLW 1

MARS 2 Design Review-Optomechanical Review

MARS 2

Mechanical DesignReview

07 Nov 2002 GLW

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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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Drive Axes

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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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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 Axes from Model

Y’

Pitch

Yaw

X

FocusCamera

SenSys

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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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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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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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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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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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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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Optical Mountsand Adjustments

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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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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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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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Isometric View of MARS2Reference

Mirror

Beam splitter Cube

Collimator Lenslet

Knife Edge

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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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CCAS Components

Frame stiffener

Dampening material

Base plate

12-inch I-beam

members

Electronics rack

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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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Unknowns

• Tolerance analysis• Metal finishing-is it needed?

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Top View of MARS2

Camera Lenslet

ReferenceMirror

Knife Edge

Collimator Pellicle

Beam splitterCube

SenSys Camera

Light Source

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Relative Axis LocationsSide View

Y

Focus

Y’

Yaw

Pitch

Camera

SenSys

X

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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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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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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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Beam Splitter Mount

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Collimator Mount

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Lenslet/Camera Mount

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Knife Edge Mount

mars 2 design review-optomechanical review 07 nov 2002 glw1 mars 2 mechanical design review

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