PFIS Waveplate Mechanism SPECIFICATION SALT-3130AE VERSION 1.1 February 2002

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Imogene Wood
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1 PFIS Waveplate Mechanism SPECIFICATION SALT-3130AE-0006 VERSION 1.1 February Scope 1.1 Identification This document covers the design of the Wave Plate Mechanism for PFIS. In it are detailed the specifications, operational modes and details of the design choices that were made to operate these modes. 1.2 System Overview The Waveplate Mechanism is the mechanism that positions the waveplates or blank optics (when not performing polarimetry) in the PFIS beam. The mechanism allows for the following three configurations of optics, i) ½ Waveplate and ¼ waveplate in beam ii) ½ Waveplate and single blank iii) Double blank The waveplate mechanism must also rotate the waveplates through discrete angles between exposures. 1.3 Document Overview This document first details the functional (science) requirements, then the technical (physical) requirements and then details the design of the mechanism and sub mechanisms Referenced Documents SALT-1000AS0007 SALT System Specification SALT-1000AA0030 SALT Safety Analysis SALT-3120AA0003 Polarimetric Optics Design Study SALT-3170AE0005 PFIS Safety Analysis SALT-3140AE0015 Interlock Specification and Design Document SALT-3140AE0020 Actuators and Sensors SALT-3130AE0002 PFIS Mechanical Overview SALT-3130AE0003 PFIS Pneumatics Overview Document Doc No. SALT-3130AE

2 3. Functional Requirements 3.1 Schematic Diagram a d b c a: ½ Wave Plate b: ¼ Wave Plate c: ¼ Wave Plate Blank d: Full Blank 3.2 Operational Modes No Polarimetry: Full Blank (d alone) Linear: ½ Wave Plate + ¼ Wave Plate Blank (a & c) Circular: ½ Wave Plate + ¼ Wave Plate (a & b) All Stokes: ½ Wave Plate + ¼ Wave Plate (a & b) 3.3 Speed into Position The maximum insertion (mode changeover) time is 6 sec. 3.4 Rotation Speed It is required that both the ½ and ¼ waveplates be able to rotate through 45 o in sec (TBD). Motion in both directions of rotation. 3.5 Rotation Repeatability Rotational positioning of both wave plates must be repeatable to the same angular position in steps of 360/32 degrees to 3 arcminutes. The position must be held to this tolerance for the entire length of the observation. Doc No. SALT-3130AE

3 4. Technical Requirements 4.1 Interfaces The Wave plate mechanism will be bolted to the collimator tube and the PFIS structure. The envelope of the mechanism will be approximately 750*300*54mm centered on the optical axis. The z envelope is 55mm deep inside the beam to clear the optics above and below the waveplates. 4.2 Physical Characteristics Mass Estimate The Mechanism currently has a mass of 11.05kg. The current estimate breakdown is given in the parts list appendix Materials used and Properties The baseline material for the mechanism body will be Aluminium. The gears will be Aluminium and the bearings Steel. The lubrication of the bearing needs to be carefully considered; the possibility of a self-lubricating bearing will be investigated. 4.3 Geometric Requirements Dimensions of Optics 110mm ½ Wave Plate 12mm 65mm ¼ Wave Plate 12mm 110mm ¼ Wave Plate Blanks 12mm 110mm Full Blank 24mm Doc No. SALT-3130AE

4 4.3.2 Position of Optics The distance from the focal plane to the ½ wave plate is 92.25mm Gap: 34mm Focal Plane 4.4 Positional Tolerances Wave Plates Location Tolerances: X & Y: 0.1mm Z: 0.1mm Tip/Tilt: 5 arcminutes 4.5 Drive Requirements Maximum Heat and Power Output The Power and temperature requirements of the SALT Telescope as set out in SALT System Specification Section, shall be adhered to Encoding The position of the wave plate must be known to 3 arcminutes. An in-position signal shall be delivered before the observation can start. The position of the detent which controls the fine positioning will be know as in or out of contact to 0.1mm. 4.6 Safety All mechanisms shall be designed such that electrical or software malfunctions cannot damage any hardware. Pneumatics should hold there position or return to a designated safe position during a power failure and solenoids should fail in a clamped position Doc No. SALT-3130AE

1 Science Configuration Layout These are the three

5 5. Design 5.1 Layout Science Configuration Layout These are the three science configurations, the position is controlled by the 3 pneumatic actuators. No Waveplates ½ Waveplate Only ½ & ¼ Waveplates Doc No. SALT-3130AE

Stepper Motor Encoder Ring Encoder Head Bearing Lens

6 5.1.2 ½ Waveplate Sub-Assembly Detent Alignment Pin Gear Side View Encoder Side View Base ½ Waveplate Stepper Motor Encoder Ring Encoder Head Bearing Lens Mount (cut views made in older model) Doc No. SALT-3130AE

7 5.1.3 ¼ Waveplate Sub-Assembly Outer Structure Blank ¼ Waveplate Double Blank Gear Pinion Lens Retainer Lens Cup Lens Holder ¼ Waveplate Doc No. SALT-3130AE

5.1.5 Outer Assembly Attach points to guider mount

2 Configuration Actuators Hard Point Connector Pneumatic

actuators back to back, we are able to position the quarter

8 5.1.5 Outer Assembly Attach points to guider mount Adjustable end stops Outer Box Rail Slit for Pneumatic 5.2 Configuration Actuators Hard Point Connector Pneumatic Actuator Adapter Kit Pneumatic Actuator Rail Using two actuators back to back, we are able to position the quarter wave plate subassembly in two discrete positions Doc No. SALT-3130AE

The speed, torque and current drawn are given in the figure below. The gear ratio is 6:1.

9 5.3 Rotation Gear Detent Pinion Encoder Stepper Motor The motor selected for this application is an Oriental Motors PMC35A3. The speed, torque and current drawn are given in the figure below. The gear ratio is 6:1. Tests are being carried out to establish the maximum acceleration of the rotation to determine the fastest possible wave plate rotation. Doc No. SALT-3130AE

10 5.3.1 Encoding Active Detent Detent Linear Bearing Pneumatic Actuator 5.4 Motion Control Rotation The rotation motion is provided by a stepper motor, which is geared to the wave plate through a 6:1 gear ratio. A small pneumatic actuator drives a detent, which provides the final high precision motion to the waveplate. Encoding The encoding of the waveplate rotation is done in a number of steps. 1) The Waveplate turns until the index marker on the optical disk encoder is found. 2) The Encoder is indexed. 3) The encoder in a closed loop with the stepper motor controls the motion to within 1 step of the required position. 4) The motor is turned off and the detent is fired 5) A proximity sensor confirms that the detent is in position. For the next motion, the detent is released and the process is repeated from step 3. Linear Motion (Mode Change) Motion Three linear pneumatic actuators (FESTO ADVU A-P-A) provide the three discrete science mode positions. Encoding Position sensors (FESTO SME-8-K-24) attached to the pneumatic cylinders provide home and end position sensing Interlocks For rotation motion, the detent must be released QWP actuator 2 cannot extend unless the HWP actuator has been extended. Doc No. SALT-3130AE

11 6. System Air, Power & Signal Requirements 6.1 Air 12 l/min at 6bar. This will be the usage during a mode changeover. 6.2 Electrical Power Item Quantity Power Voltage Max Duty Cycle Stepper Motor 2 7.2W (with driver) 24V 50% Solenoid W 3V-24V 10%-50% Pneumatic Valve W 24V Change of Modes Maximum Heat and Power Output: Current Estimate of power output from actuators is: 7.2W for each of two stepper motors and 3W for each of two solenoids. Motors shall be powered down during holding and thus only draw power during rotation. The solenoids power will draw 30W for 0.02s and 3W for 0.20s. 6.3 Logic Item Quantity Resolution Optical Encoder Incremental 2 1µm/count Proximity Sensor Reed switch, magnetically actuated 6 0.1mm Proximity Sensor- (for detent TBA) 4 0.1mm Absolute position of the wave plate must be known to 3 arcminutes. An in-position signal shall be delivered before the observation can start. The position of the detent solenoid and the positioning pneumatics will be know only as in or out with no intermediate position sensing. Doc No. SALT-3130AE

12 Sub-Assembly Part Name Part Number/Drawing Number Quantity Type Supplier Material Mass/Ite m Price/Item Quarter Wave Plate QWP-Base 1 M Aluminium QWP-Optic 1 O Optic QWP-Glass 1 O Optic QWP-DoubleBlank 1 O Optic QWP-LensMount 1 M Aluminium QWP Ball Bearing K08008XP0K 1 C KAYDON Steel QWP Lens Cup 1 M Aluminium QWP Lens Retainer 1 M Aluminium QWP-OuterRing 1 M Aluminium QWP-InnerRing 1 M Aluminium QWP-6" Gear F24A C* WM BERG Aluminium QWP-11/4"Pinoin F24A C WM BERG Aluminium Stepper Motor PMC35A3 1 C ORIENTAL MOTORS $250 Rotary Disk Encoder Custom 1 C* Micro-E Glass Encoder Hub (111mm) 1 M Aluminium Encoder Read Head M C* Micro-E Aluminium Encoder Read Head Mount 1 M Aluminium Thread in Detent Pneumatic EGZ C FESTO Detent Guide Runner ND C Schneeburger Steel Detent 1 M Aluminium Detent Pin 1 M Hardened Steel Linear Bearing Runner MR C PACIFIC BEARING Steel (DIN 17230)/ Plastic Mandrel SliderShim 4 M Aluminium QWP-Pusher 1 M Aluminium Half Wave Plate HWP-Base 1 M Aluminium HWP-Optic 1 O Optic HWP-LensMount 1 M Aluminium HWP Ball Bearing K012008XP0K 1 C KAYDON Steel HWP Lens Cup 1 M Aluminium HWP Lens Retainer 1 M Aluminium HWP-OuterRing 1 M Aluminium HWP-InnerRing 1 M Aluminium HWP-6" Gear F24A C* WM BERG Aluminium HWP-11/4"Pinoin F24A C WM BERG Aluminium Doc No. SALT-3130AE

13 Stepper Motor PMC35A3 1 C ORIENTAL MOTORS $250 Rotary Disk Encoder Custom 1 C* Micro-E Glass Encoder Hub (90mm) 1 M Aluminium Encoder Read Head M C* Micro-E Aluminium Encoder Read Head Mount 1 M Aluminium Thread in Detent Pneumatic EGZ C FESTO Detent Guide Runner ND C Schneeburger Steel Detent 1 M Aluminium Detent Pin 1 M Hardened Steel Linear Bearing Runner MR C PACIFIC BEARING Steel (DIN 17230)/ Plastic SliderShim 4 M Aluminium HWP-Pusher 1 M Aluminium Outer Assembly OuterBox 1 M Aluminium MountPlate 2 M Aluminium PneumaticCylinder 150mm Stroke ADVU A-P-A 3 C FESTO ADVU-Adapter DPVU-12/16 1 C FESTO QWP Rail MR ,611mm 2 C PACIFIC BEARING Steel (DIN 17230) HWP Rail MR ,281mm 2 C PACIFIC BEARING Steel (DIN 17230) PneumaticRail MR ,401mm 1 C PACIFIC BEARING Steel (DIN 17230) OuterSliderShim 2 M Aluminium PneumaticHardpoint 1 M Aluminium M - Manufactured O - Optic C - Commercial off the Shelf C* - Commercial off the Shelf with Modifications Doc No. SALT-3130AE

PFIS Filter Mechanism SPECIFICATION SALT-3130AE VERSION February 2003

PFIS Filter Mechanism SPECIFICATION SALT-3130AE-00012 VERSION 1.0 16 February 2003 1. Scope 1.1 Identification This document covers the design of the Filter Mechanism for PFIS. In it are detailed the specifications,