PFIS – Mechanical Overview VERSION 1.0 10 March 2003 cdr... · Mechanical Overview Document...

Mechanical Overview Document

SALT-3130AE-0002 1

PFIS – Mechanical Overview

SALT-3130AE-0002

VERSION 1.0 10 March 2003

1. Scope This document provides an overview of the mechanical design of PFIS. In it the structure, mechanisms and overall mass properties are introduced. 1.1 Identification This document gives an overview of the mechanical design of PFIS and details how the mechanical aspects of the instrument piece together. 2. Referenced Documents SALT-3110AE0002 PFIS Structure Specification SALT-3130AE0005 Slitmask Mechanism SALT-3130AE0006 Wave Plate Mechanism SALT-3130AE0007 Grating Mechanism SALT-3130AE0008 Shutter Mechanism SALT-3130AE0009 Etalon Mechanism SALT-3130AE0010 Grating Mechanism SALT-3130AE0011 Beam Splitter Mechanism SALT-3130AE0012 Filter Mechanism SALT-3130AE0012 Articulation Mechanism


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3. Mechanism Layout 3.1 Front Isometric View Filter Mechanism

Grating Mechanism

Camera Tube

Collimator Tube


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3.2 Bottom View

Articulation Mechanism

Slitmask MechanismPFIS Mount Feet (1 x,y,z pinned, 1 y,z slot and 10 z pads)

Wave Plate Mechanism

Baffling


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3.3 Back Isometric View

Beam Splitter Mechanism


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3.4 Front Isometric View Without Structure

Articulation Mechanism

Filter Mechanism

Grating Mechanism

Fold Mirror

Etalon Inserter Mechanism

Slit Mask Mechanism

Beam Splitter Mechanism

Collimator Optics Cells

Wave Plate Mechanism

Grating Rotator


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Articulation Hubs

4. Structure The PFIS structure consists of an open-truss welded invar structure. It is designed to accommodate the following key components: 1) The PFIS Structure must be attached to the Prime Focus Instrument Platform, which is a 1800mm diameter ring. 2) The collimator tube that holds all the collimator optics and is in the center of the instrument. The collimator is stationary 3) The two cameras, the Visible and IR Cameras. These cameras are at right angles to the collimator and also articulate around the VPH Grating disperser. For articulation, they sweep out an angle of 100 degrees. Other key considerations in the design of the structure were minimizing the mass and ensuring that the structure was stiff enough to meet the image motion specification. The structure is made out of thin-walled square invar tubes. Invar was chosen based on its very good thermal expansion properties, which allowed us to negate the effect of thermal expansion on the performance of the instrument. Careful consideration was given to the flexure of the instrument, to ensure that flexure due to the varying gravity vector did not cause excessive image motion. To this end, a full Finite Element Analysis was carried out and is detailed elsewhere. The Structure is mounted to the PFIP platform using 12 mounting pads. The PFIP platform is made out of steel and therefore has very different thermal expansion properties to PFIS. For this reason a kinematic configuration of the mount feet is required. The articulation of the cameras is about two points (hubs) on the top of the structure. The hub is integral to the PFIS structure. The camera rides on a curved rail, which is also an integral part of the PFIS structure. The PFIS structure has mounting points positioned on it for the attachment of the electronics boxes, the fold mirror and some of the mechanisms.

Collimator Tube

Mount Feet


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5. Mechanisms The mechanisms on PFIS are required to change science modes and to facilitate the changing of slitmasks, gratings, and filters during normal telescope operation. Because PFIS is at the prime focus, it is required that all mechanisms be remotely operated and only require SALT personnel to attend to them (to change slitmasks in the magazine etc) every few days. The general principles of designing the mechanisms are as follows. The motions are controlled by stepper motors (where a range of positions are required) or by pneumatics (where one or two discrete positions are required). The mechanisms are designed to produce a minimal amount of heat by; sizing motors to be as small as possible, ensuring that the duty cycle is low, by having brakes and detents to hold positions and by using pneumatics wherever possible. Every motion is encoded, pneumatics just with home and end position sensors and motors have encoding over their entire operating range. What now follows is a very short description of what each mechanism does (in the order that they are on the optical path): 5.1 Slitmask Mechanism The slitmask mechanism selects and changes one of 30 multislits or 10 longslits from the slitmask magazine and inserts it into the beam at the telescope focal plane. The mechanism consists of a magazine, a carrier/selector mechanism and a pneumatic inserter.

Focus Subassembly Carrier Subassembly

Magazine

Elevator


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5.2 Waveplate Mechanism The waveplate mechanism selects the wave plate configuration (either blank, ½ waveplate or ½ and ¼ waveplate). During observations in polarmetric modes, it rotates the wave plate(s) between exposures by discrete angles. The mechanism consists of two base plates with optics mounted on them that are mounted on a linear slide. Pneumatic actuators select between three configurations. Small motors mounted on the base plates rotate the waveplate optics on small precision ball bearings. 5.3 Shutter The shutter is an off-the-shelf Prontor 150mm shutter. It will be modified to open up the aperture to 162mm. A pneumatic actuator will be fitted to hold the shutter open during long exposures so that the solenoid can be switched off.

½ Waveplate

½ Waveplate

Configuration Pneumatics

Rotation System


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5.4 Grating Mechanism The grating mechanism inserts one of 6 gratings into the beam at the pupil. When one of the gratings is in position, the grating rotator rotates it to the required angle for the observation. The grating mechanism consists of a magazine on a frame and slide, an insertion pneumatic and the grating rotator stage. 5.5 Beam Splitter Inserter The beam splitter mechanism inserts and removes the beam splitter from the beam. The 18 beam splitter prisms are mounted in their mount, which is attached to linear slide. A pneumatic actuator inserts and removes the beam splitter.

Rotation Sub-Assembly

Grating and Holder

Structure

Magazine Selector Sub-Assembly

Prism Holder

Slide Rails

Camera Tube

Camera Front Flange

Pneumatic Actuator


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5.6 Filter Mechanism The filter mechanism selects and inserts one of 20 filters from the filter magazine and inserts it into the beam just before the detector. The mechanism consists of a magazine on a linear stage, which moves the magazine to line the required filter up with the inserter, and the pneumatic inserter. 5.7 Articulation Mechanism The articulation mechanism articulates the camera tube (and all that is attached to it – detector, filter mechanism, grating mechanism) from 0 to 100 degrees. The articulation mechanism consists of the cradle and frame that supports the camera tube on the articulation bearing and I-beam rail, a motor/gearbox drive assembly and a precision positioning detent assembly.

Magazine

Stage

Camera Tube

In Position Assembly

Stationary Face Plate

Sliding Face Plate

Camera Cradle Beams

Articulation Rail

Detent Sub assembly

Detent Rail Flexible Gear Rack

Drive sub-assembly


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6. Mass Properties 6.1 Mass Estimate Since PFIS is part of the payload on the tracker, it needs to fit within the weight budget allotted to it by the tracker. Below is set out the masses of each mechanism, the structure and all the additional equipment that will be on PFIS and make up its total mass. The mass of the IR side of the PFIS is estimated assuming that it will be identical to the visible side. Optics Struct/Mec Comments STRUCTURE Main Structure (incl collimator tube) 110 0 114 Main structure, minimum mass COLLIMATED BEAM Slitmasks 16.5 0 16.5 Based on CDR Model Field Lens 1.93 1.93 0 Z-max Lens Holder (Field Lens) 3.8 1.49 From Alan's model Waveplate 11.05 0.6 10.45 Based on CDR Model Collimated lens main group 9.31 9.31 0 Z-max Lens Holder (Collimated beam) 10.5 0 10.7 From Alan's model Mirror Mechanism 12.092 2.462 9.63 PDR Estimate (looks conservative)Guider Mount 5 5 Based on CDR Model 70.182 VISIBLE BEAM Focus Mechanism 13.63 5.53 8.1 From Alan's model Shutter 3 0 3 Weighed it +400g for pneumatics Etalon 1 20.86 17 3.86 PDR Estimate VPH Grating 25.595 11.295 14.3 Based on CDR Model Etalon 2 20.86 17 3.86 PDR Estimate Polarizer 4.425 0.9 3.525 Based on CDR Model Camera Optics 31.6 31.6 0 Z-max Lens Holders 19.2 0 19.2 From Alan's model Filters 15.84 4 11.84 Based on CDR Model CCD Camera 8.5 0 12 SAAO CDR Articulation 17.1 0 17.1 Based on CDR Model Camera Tubes 3 0 3 2mm thick aluminium tubes 183.61 IR BEAM Focus Mechanism 13.63 5.53 8.1 From Alan's model Etalon 1 20.86 17 3.86 PDR Estimate VPH Grating 25.595 11.295 14.3 Based on CDR Model Etalon 2 20.86 17 3.86 PDR Estimate Polarizer 4.425 0.9 3.525 Based on CDR Model Camera Optics 31.6 31.6 0 Z-max


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Lens Holders 19.2 0 19.2 From Alan's model Filters 15.84 4 11.84 Based on CDR Model CCD Camera 8.5 0 12 SAAO CDR Articulation 17.1 0 17.1 Based on CDR Model Camera Tubes 3 0 3 2mm thick aluminium tubes 180.61 PXI Cold Box 3 PSC1 Cold Box 3 PSC1 Cold Box 3

Pneumatics Control & Pipes 3 Current Estimate - 12 Actuators, 30m Piping

Wiring 4 Guess Connectors and Miscellaneous Electronics 5 Guess

PXI Chassis with Power Supply 8.84 Measured (5.8 box and cards, Power 3)

CCD Controller Power Supply 24 598.242 188.952 364.34


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7. Electronics Boxes Below is a preliminary layout of the electronics boxes.

PXI Box PSC-2 Box

PSC-1 Box

Detector Electronics Box

Structure

SALT-3110AE-0002 1

PFIS – Structure

SALT-3110AE-0002


1. Scope This document provides details of the PFIS Structure and its components. It also contains drawings of the structure and the invar sections to be used. 2. Referenced Documents SALT-3110AE0003 PFIS Structure FEA Document SALT-3130AE0002 Mechanical Overview SALT-1520AS0002 PFIS Interface Control Document

Structure

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3. Overall Layout To see the structure in context, here is the structure will all mechanisms attached Filter Mechanism

Grating Mechanism

Camera Tube

Collimator Tube

Structure

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4. Structure Design The PFIS structure consists of and open-truss welded invar structure. It is designed to accommodate the following key components: 1) The PFIS Structure must be attached to the Prime Focus Instrument Platform, which is a 1800mm diameter ring. 2) The Collimator tube that holds all the collimator optics and is in the center of the instrument. The Collimator is stationary 3) The two cameras, the Visible and IR Cameras. These cameras are at right angles to the collimator and also articulate around the VPH Grating disperser. For articulation, they sweep out and angle of 100 degrees. Other key considerations in the design of the structure were minimizing the mass and ensuring that the structure was stiff enough to meet the image motion specification. The structure is made out of thin-walled square invar tubes. Invar was chosen based on its very good thermal expansion properties, which allowed us to negate the effect of thermal expansion on the performance of the instrument. Careful consideration was given to the flexure of the instrument, to ensure that flexure due to the varying gravity vector did not cause excessive image motion. To this end, a full Finite Element Analysis was carried out on the structure and the flexure at various key optical points in the structure was predicted under various loading conditions. The sensitivity of the optics to these motions was then used to predict the image motion at the detector and the result of this analysis was compared to the image motion spec to determine if the structure was sufficiently stiff. In this way the structure was optimized to meet the stiffness specification and to have as low a mass as possible. A full description of the FEA on which this design is based is given in the PFIS Structure FEA Document. 4.1 Structural Layout To explain the construction of the full structure (shown here) it will be broken up into sub-sections

Structure

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4.1.1 Base Ring The base ring provides the surface off which the structure is built. The 12 mount feet are attached to the bottom of the base ring. The star shaped cross struts provide rigidity on the PFIP plane as PFIP does not provide any rigidity in x-y since we have a kinetic mount to negate thermal expansion mismatch.

4.1.2 Articulation Hub and Rail The hub and rail provide the table on which the camera articulates. Truss members connect the hub and rail. The hub provides a mounting point for the shaft around which the articulation bearing fits. The I-beam rail is a 650mm bent invar I-beam. The top surface of the I-beam and the bore of the articulation hub will be machined post heat treatment to a tight tolerance.

Structure

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4.1.3 Support Trusses These truss elements give the PFIS structure its depth and provide stiffness in the z- direction.

4.1.4 Collimator The collimator tube and supports are integral to the structure

Structure

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4.2 Mounting to PFIP The Structure is mounted to the PFIP platform using 12 mounting pads. The PFIP platform is made out of steel and therefore has very different thermal expansion properties to PFIS. For this reason a kinematic configuration of the mount feet is required. To achieve a kinematic mount with the 12-footed structure, 10 of the feet are z-pads, 1 foot is a pin and 1 is a slot. This ensures PFIS stays on the PFIP plane, which defines the telescope focal plane, while allowing its diameter to change compared to that of PFIP. Since the guider is attached to PFIS, motions on the PFIP plane will be ‘guided out’. The feet are shown below The pin foot mates (with a very close fit) with a fat circular rod, which will be built into a similar plate attached to PFIP. The through bolt holes are oversized so as to allow rotation around the pin. The mating plate will be machined and fitted to PFIP to align PFIS to the telescope. The slot foot works in a similar way but because it is slotted it allows PFIS to ‘grow’ along the line between the pinned and slotted foot. The pad feet have oversized holes and allow movement in x and y. In z-they are tightened down with Belleville springs and will have low friction coatings. Thus they will be firmly held against PFIP but will be free to slide in x and y. Pin Slot Pad 4.3 Mounting of the Articulating Cameras The articulation of the cameras is about two points (hubs) on the top of the structure. The hub is integral to the PFIS structure. The camera rides on a curved rail which is also an integral part of the PFIS structure. The PFIS structure has mounting points positioned on it for the attachment of the electronics boxes, the fold mirror, some of the mechanisms.

Structure

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Structure

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Structure

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Structure

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Structure Finite Element Analysis Document

SALT-3110AE-0003 1

PFIS – Structure Finite Element Analysis Document

SALT-3110AE-0003


1. Scope This document provides an explanation of the modeling method and assumptions for the finite element analysis of the structure. It also describes the method of post-processing the deflection results and gives a summary of the image motion analysis results obtained. 1.1 Identification This document gives an overview of the mechanical design of PFIS and details how the mechanical aspects of the instrument piece together. 2. Referenced Documents SALT-3110AE0002 PFIS Structure Specification SALT-3130AE0002 Mechanical Overview Swales/UW PDR SALT Telescope Instrument Structure Analysis – SAI-RPT-438


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3. Modeling A Finite Element Analysis of the structure was performed to ensure that it met the flexure specifications and to find where mass could be removed from the structure without compromising the stiffness. The analysis was undertaken using the FEA simulation module of Ideas. Since the structure was already modeled in Ideas it was easy to get the geometry into its FEA module. Images of the PFIS FEA model in wire frame and solid rendering 3.1 Elements 3.1.1 Truss Structure All the structural beams were modeled using beam elements. The cross sections of the beams were modeled accurately using the dimensions of Invar square tube we have already found a vendor for.

Visible Camera

IR Camera

CollimatorPFIP Ring


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The three sections used were 1in x1in with 0.4wall, 1.5in x1.5in with 0.4wall and 2in x2in with 0.4wall. In the end, the following sections were chosen for the different sections of the structure. (This was an itterative process of trying different cross-sections for different trusses and analysing the flexure.) For the Base of the PFIS structure, 2in x2in with 0.4wall beams were used: For the trusses that support the articulation hubs, 1.5in x1.5in with 0.4wall beams were used: The trusses that support the I-beam rail are 1in x1in with 0.4wall beams. The I-beam is also modeled as a beam element with the following section: h= 53.4mm, w=39mm and the web and flange thickness is 4mm


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3.1.2 Camera and Collimator Tubes The camera and collimator tubes were modeled using thin shell elements supported by square tube beam elements. Camera Collimator 3.1.3 Optics All optics were modeled as a lumped mass and tied with constraint elements of the camera tubes in a way that represented the anticipated method of attachment. (note: it will be important to keep track of the way that the optics are mounted in the final design and if this varies significantly from the assumptions made here, the FEA will need to be re-run to ensure the model is still valid). The optics nodes and elements are stored in an element set to be able to easily pull out their deflections for further optical sensitivity analysis. (One of the main objectives of this analysis is to isolate the deflection of these optical elements for further analysis)

Camera Cells

Fold Mirror Collimator Focus Cell

Collimator Cells


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3.1.4 Mechanisms All mechanisms are modeled as lumped masses and attached to the structure as the will be attached to the PFIS structure. 3.1.5 PFIP Ring The PFIP ring is modeled as beam elements. The section of these beams has been chosen so as to give the deflection that SALT have specified as the deflection of PFIP, i.e. a maximum peak to valley deflection of 10microns. 3.2 Materials The main structure has been modeled using the mechanical propertied of Invar 36. This includes the base, all truss elements, the collimator tube and the I-beams. The camera tubes and articulation camera cradles are modeled using the mechanical properties of Aluminium 6061 T6. The PFIP Ring is modeled as steel. All materials have been assumed to be acting in their linear elastic range for all loads that will be applied.

Telescope Focal point

Slitmask

Shutter

Grating

Etalons

Waveplate Guider

Articulation

Beam Splitter

Dewar


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3.3 Boundary Conditions 3.3.1 PFIP-Hexapod Actuators PFIP is pinned at three points 120 degrees apart. This represents the 3 hard connection points of the hexapod actuators. For analyzing the anticipated deflections as PFIP rotates, 4 restraint sets are created to represent the changing position of the hexapod hard points as PFIP rotates in 30-degree increments (note due to symmetry there are only 4 unique positions for 30-degree increments). 3.3.2 PFIS to PFIP PFIS is attached to PFIP by constraining specific nodal degrees of freedom on the PFIS mount feet to the corresponding nodes on PFIP (constrained degrees of freedom in yellow). At the pinned foot, x, y & z degrees of freedom are constrained. At the slotted foot, x & z degrees of freedom are constrained and on all other 10 feet, only the z degrees of freedom are constrained

Pinned Foot

Slotted Foot

Z- Pad Feet (10 of)


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3.3.3 Cameras to the articulation bearing and the I-beam rail The camera arms are connected by beam elements to the articulation hub. The camera ‘rollers’ are connected to the I-beam rail using constrained degrees of freedom. One is restrained only in z, representing the cam roller on the rail and the other (the outer roller) is constrained in z and y, representing the combination of the cam roller on the I-beam and the detent stopping rotation. 3.4 Loading The model is loaded with gravity only. Three gravity cases are set up, with the gravity vector in the X, Y and Z directions. Thus for each of the 4 restraint condition sets, the model is solved for three gravity cases. Since the structure deflection is assumed to be linear over the full range of loading, we are able to calculate the deflection under any complex gravity vector by proportioning the deflection according to the actual load vector. This allows us in post-processing to get the deflection as PFIP rotates and tracks between 31 and 43 degrees. 4. Post Processing The Fortran 77 program that was used for PDR estimates of image motion was modified slightly to be used to analyze the Ideas flexure data. For a full description of the Fortran program written by Swales Aerospace, please see the relevant document in the PDR package. For CDR purposes, the following changes were made to the code: -The data reading code was altered to be able to read in Ideas generated deformation reports.

Z, Y d.o.f. constrained Z d.o.f. constrained

Beam Elements Connected


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- The number of sampling points for the rotation stage was reduced from every 10 degrees to every 30 degrees to facilitate faster processing of the models. (Ideas does not handle batch processing of many boundary condition sets very well and reducing the number of models solutions for each iteration from 36 to 12 was necessary in the interests of speed). A comparison study showed that this had little affect on the final results. The sensitivity matrix was updated from Z-max to reflect the changes in the optics design. 5. Results The results of the Finite Element Analysis were post-processed to model the actual image motion at the detector during realistic track trajectories. The motion of the following nodes was used in this analysis:

• Telescope focal plane optic axis (reference node).

• Field lens

• Collimator main group.

• Fold Mirror

• Collimator doublet

• Camera group 1

• Camera group 2

• Detector

All motions were referenced to the focal plane optic axis, since the telescope guider removes the effects of flexure there. The ZEMAX optical CAD program was used to calculate the sensitivity of image motion at the detector to motions in all six degrees of freedom for each optical node. The net image motion for each FEA run is calculated by matrix multiplication of the node motion with the optical sensitivity matrix. Image motions perpendicular and parallel to the direction of dispersion were tracked separately. FEA results were calculated for a three-dimensional grid of instrument orientations: optic axis at 37 degrees elevation (telescope center position) and a cone of radius 6 degrees around the center (extreme track). For each track position the instrument was permitted to rotate a full 360degrees about the optic axis (angle φ). Figure 1 illustrates the image motion for the model as a function of rotation φ, for tracker position fixed at the center and at four extremes of the track cone. It is seen that instrument rotation is the largest flexure effect (25 : peak-to-peak over +-180degrees rotation), and track position is roughly 3 times less important. The flexure is comparable in -60

-50

-40

-30

-20

-10

0

10

-30 -25 -20 -15 -10 -5 0 5 10

Dispersion Direction

Perp

endi

cula

r to

Dis

pers

ion

center090180270


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the dispersion and cross-dispersion direction.

To examine the predicted image motion for the visible beam over a realistic track, the track vector at the entry and exit from a +-6 degree track at each of 6 declinations from +5 degrees through –70degrees was calculated, and the amount of field rotation during the track ∆φ was calculated. A worst case image motion for each declination was then found among all possible φ(in), φ(out) pairs. Figure 2 presents the worst case visible-beam image motion for the model. The function is double valued because the track geometry is different for the rising and the setting tracks through the SALT availability annulus. We see that the worst-case image motion is well within the specification for the model, for the structure perpendicular to the dispersion. The worst-case motion parallel to the dispersion is out of specification for extreme tracks. We believe that this is due to a the motion being very sensitive to the camera design which is not yet completed and there may be room to improve the stiffness as the camera elements are added.

Perpendicular to Dispersion

0

10

20

-80 -60 -40 -20 0 20

Declination (deg)

mic

rons

/ tra

ck

Spec

Parallel to Dispersion

0

10

20

-80 -60 -40 -20 0 20

Declination (deg)

mic

rons

/ tra

ck Spec

Slitmask Mechanism Specification

Doc No. SALT-3130AE-0005 1

PFIS – Slitmask Mechanism

SPECIFICATION

SALT-3130AE-0005

VERSION 1.1 17 February 2003

1. Scope 1.1 Identification This document covers the design of the Slitmask Mechanism for PFIS. In it are detailed the specifications, operating criteria and design of the mechanism. 1.2 System Overview The Slitmask Mechanism is the mechanism that selects one of 30 multislits or one of 10 longslits from the slitmask magazine and positions it at the focus of the telescope. 1.3 Document Overview This document first details the functional (science) requirements, then the technical (physical) requirements and details the design of the mechanism and sub mechanisms. 2. Referenced Documents SALT-1000AS0007 SALT System Specification SALT-1000AA0030 SALT Safety Analysis SALT-3150AA0001 Slitmask Requirements and Fabrication Document 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



3. Science Requirements 3.1 Schematic Diagram 3.2 Geometry 3.2.1 Multi Slits Maximum mask clear aperture: 107mm (8 arcmin at 4.46 arcsec/mm FP plate scale) Thickness: 100µm Number of multi slits: 30 3.2.2 Reflective Long Slits: Dimensions:

Slit widths range from 0.5—3.0 arcsec: 0.11—0.67mm Slit lengths: Most will be full field (i.e. 107mm), but need:

- ½ length clear for Frame Transfer mode - ½ length clear (centered) for Spectropolarimetry

Total number of long slits: 10

Focal Plane

Optical Axis

Slitmask Holder

Carrier

Magazine 10 x Longslits30 x Multislits



3.3 Speed into Position and Duty Cycle Time to change slit masks: <1 min No. of changes per evening: 8-12 (i.e. probably not more than 1 slit per track/target)

+ 8-12 daytime calibrations. 3.4 Positional Repeatability and Alignment Tolerance specs (long slits and multi-slits): The Slitmask must be positioned on the focal plane of the telescope. Rotations: X,Y: 4 arcmin (140 micron end-to-end) absolute (primarily for multi-

Slits, long slits can be weaker) Z: 1 arcmin (35 micron end-to-end) absolute actually need only be

as good as CCD chip alignment Translations: X,Y: 30 micron repeatable, machine tolerance absolute

Z(sag): 65 micron absolute (can probably loosen up here to ~200 micron, need to check w/ZEMAX)

Note: Once a multi-slit mask has been removed from its frame, we can not expect that it can be reinserted into a frame with the same absolute position. Any mask inserted into a frame will be considered a new mask, and should be treated as such. 3.5 Operational Modes The mechanism must be able to select any one of 30 multi slits or 10 long slits and position it at the focus. Each mask will be placed in the beam at least twice, the first for daytime calibrations and then secondly for the nighttime observation. 4. Technical Requirements 4.1 Interfaces The focus sub-assembly will attach to the holder of the first collimator element (the guider mount) and will provide high positional accuracy to the position of the collimator optics and the guider. The elevator and magazine sub-assemblies will be attached to the PFIS structure to a less stringent positional accuracy.



4.2 Physical Characteristics 4.2.1 Mass Estimate The Mechanism currently has an estimated mass of 16.5kg (including masks). The current estimate breakdown is given in the parts list appendix. 4.2.2 Materials used and Properties The baseline choice of material will be aluminium but invar will be considered for high position tolerance areas due to its low CTE. 4.3 Geometric Requirements 4.3.1 Position of Mechanism and Envelope The slits must slide in parallel to the x-axis of the instrument. The final position of the mask is to be center at the focus of the telescope. The magazine and carrier need to fit into an envelope, within the structure. This envelope is defined by the wave plate mechanism and camera tube in –x, the hexagon of the structure in the +x, y and -y, other structural members in +z, and 10mm below the focal plane in -z. The focus pusher actuator is stationary in z and has thus been allowed to fit below this envelope.



4.3.2 Dimensions of Slitmask The multi slits (in holder) should be less than 6mm thick and the long slits less than 9mm thick. This to ensure all the slits stowed in the magazine fit within the space constraint. 4.4 Positional Tolerances The positional tolerance of the optical elements is detailed in section 3. The other sub-systems will be positioned and aligned so as to allow smooth and unobstructed sliding of the mask holders between them. Typically the mechanisms will be aligned to within 100µm of each other. The magazine holder and the linear stage will have adjustable mounts to ensure alignment. 4.5 Drive Requirements 4.5.1 Maximum Heat and Power Output The Power and temperature requirements of the SALT Telescope as set out in SALT System Specification Section, 5.3.2.5 shall be adhered to. 4.5.2 Encoding All motor driven stages will have full range absolute encoding while pneumatic actuators will only have position sensors at their end positions. The motor driven stage will have encoding and soft limits used for positioning while hard limit switches will stop the stage from going outside of its operating range. 4.6 Safety All mechanisms shall be designed such that electrical or software malfunctions cannot damage any hardware. Pneumatics should hold their position or return to a designated safe position during a power failure and solenoids should fail in a clamped position.



5. Description of Design 5.1 Layout

Above are shown the four main subassemblies of the Slitmask mechanism. 5.1.1 Mask and Holder Multi Slit:

Rail Rod

Focus Pusher Cutout Reference holes

Slitmask

Carrier Pusher Cutout

Focus Subassembly Carrier Subassembly

Magazine

Elevator

Magnet



The fibre-composite multi slit mask (which has been precut in a laser cutting mill) is held in the slitmask holder. The mask is indexed to the holder by two holes, one round and one elongated (which are cut at the same time as the slits) and held in position by small clamping fixtures (TBD). The carrier pusher cutout is for the actuator that pushes the mask and holder from the magazine to the carrier, and back, to engage with. The focus pusher cutout is for the actuator that pushes the mask and holder from the carrier into focus position, and back, to engage with. Long Slit: The details of the long slit design have not yet been finalized, however the rail and outer structure (with grooves) will be the same as the multi slit to facilitate using the same rails and push-pull mechanisms. 5.1.2 Focus Subassembly

A tapered chute guides the mask into 6 ball bearing rollers (with 4mm grooves) that slide and position (in y and z) the masks in the focus area. An adjustable hard stop positions the mask to the required accuracy and repeatability in x.

Rollers

Guider Mount Points

Slitmask in Holder

Chute

Adjustable end stop

Roller in Flexure



5.1.3 Elevator The elevator is made up of an ‘off the shelf’ linear stage and a standard nema 23 stepper motor. A lower efficiency high gear ratio threaded shaft is specified to eliminate the need for braking (16 threads per inch acme screw). The motion is encoded loosely using a position transducer and exact ‘floor’ indicators are given by a series of vane switches. The latch pusher attached to the bottom of the stage pushes on the carrier latch to release the mask when it is on the focus plane and ready for insertion into the beam.

Stepper Motor

Position Transducer

Linear Stage

Linear Stage Carrier

Bottom Position Latch Pusher

Vane Switches



5.1.4 Carrier Subassembly

The mask is driven into the elevator mask carrier from the magazine by a rodless pneumatic actuator. A latch, mounted to the actuator engages the mask in the magazine as the elevator moves up and down. Powering the actuator pushes the mask out and holds it

Linear Stage

Actuator Carrier

Bracket

Rodless pneumatic actuator

Actuator Mount

Mask Carrier Frame

Latch Mechanism Bottom position pusher

Vane Sensor Station Indicator

Bar Code Reader



in the carrier. As the carrier approaches the bottom of its travel (at the focus plane) a pusher pushes the latch out of the mask so that it is free to move through the carrier when acted upon by the focus actuator. Care is taken to ensure that the engaging tooth on the focus actuator is properly engaged before the latch is released. 5.1.5 Magazine

The Magazine is designed to be removable and to hold 30 multi slits and 10 long slits. The Magazine mount is attached to the PFIS structure and the magazine is clamped into the mount using wing nuts. Small magnets attached to the back of the mask holder pull up to a strip in the magazine to ensure that the masks are firmly held in the magazine until the actuator pulls them out. The pneumatic actuator, which drives the mask into the focus position, is attached to the bottom of the magazine mount.

Storage Rails 30 Multi slit 10 Long slit

Ball Detent Magazine

Magazine Mount

Pneumatic Actuator



5.2 Speed of Motion The pneumatic actuators will undergo their full range of motion in less than 4 seconds. The linear stage has a lead screw with 16 threads per inch. The maximum speed of the motor (directly coupled) is 2000 rev/min (which would provide 5 oz-in of torque which would lift 5 kg on the carrier). Twice the full travel of the linear stage – 300mm, would require 200 revolutions which would take 6 seconds, running the motor at 75% of top speed would still enable full motion in 9 sec. Stacked together the motions would take a maximum of 43 seconds the encoding time must thus be of the order of 10 seconds to ensure a mask changeover in less than 60 seconds. 5.3 Motion Control 5.3.1 Slide Mask between Magazine and Elevator Motion A pneumatic actuator (FESTO DGP-8-135-P-A-B) slides the mask frames along the rails from the magazine onto the elevator carrier (and back). The actuator is controlled by a micro-pneumatic valve (FESTO MZH-5/3-M3-L). Encoding There are proximity sensors (FESTO SME-8-K-24) at the home and extended position of the actuator. 5.3.2 Elevator Up and Down Motion The elevator motion is by means of a Stepper Motor (Oriental Motors PK266-03) driving a worm screw on a linear stage Encoding There is a Linear Cable Transducer (UniMeasure LX-PA-10k) which gives full range absolute encoding. On the elevator are vane limit switches at the top and bottom of travel and at the bottom of travel in the magazine. These give top and bottom limit stops. There is also a vane

Remove mask from focus (4s)

Elevator to mask storage position (9s)

Remove mask from magazine (4s)

Return mask to magazine (4s)

Insert mask into focus (4s)

Elevator select new mask (9s)

Elevator to focus position (9s)



switches at the bottom elevator position to indicate the in focus position and it is also used to index the absolute encoder. There is an ‘at a station’ indicators which comprise two van switches along side each other and 2 metal vaned strip with teeth at the station spacing. By off-setting vaned strips slightly we create a narrow band station indicator The ‘at a station’ indicator switch and the narrow at home switch will be achieved using two vane type hall sensors in an exclusive or arrangement to ensure narrow acceptable ranges. 5.3.3 Slide Mask between Magazine and Focus Motion Motion in and out of Focus position from the elevator carrier is by means of a pneumatic actuator (FESTO DSNU-20-250-PPV-A). The actuator is controlled by a micro-pneumatic valve (FESTO MZH-5/3-M3-L). Encoding There are proximity sensors (SMEO-4-K-24-B) at the home and extended position of the actuator. 5.4 Control Interlocks For the normal modes of operation to be executed, the following conditions must be met: 5.4.1 Remove Mask from Magazine

Elevator (E1)

Actuator 2 (A2)

Actuator 1 (A1)



For A1 to remove mask from the magazine the following conditions must be met: A1 = home A2 = home Position Transducer must give correct magazine position Station Indicator must indicate a valid station.

OK when A1=extend 5.4.2 Return Mask to Magazine For A1 to return a mask to the magazine: A1 = extend A2 = home Position Transducer must give correct magazine position Station Indicator must indicate a valid station

OK when A1=home 5.4.3 To Select a Mask in the Magazine For E1 to move up and down in magazine select mode: A1=home A2=home Use position transducer to encode to the mask to be selected. Use the station indicator to accurately find the station (ie slow down 1mm early and hunt for marked line).

OK when position transducer at correct value (to 0.5mm approx.) Station Indicator within n steps of a transition 5.4.4 Elevator Moves Full Carrier to Bottom (Focal Plane) Position For E1 to move down to Focus position: A1=extend A2=home Use position transducer to encode motion down to bottom Slow down 1mm early and find elevator bottom proximity switch

OK When E1=bottom 5.4.5 Elevator Moves Full Carrier to an Empty Magazine Position For E1 to return mask to it’s magazine position: A1=extend A2=home Use position transducer to encode to the correct magazine position of the mask in the carrier. Use sliding vane switch to accurately find mask position (ie slow down 1mm early and hunt for edge).

OK when position transducer at correct value (to 0.5mm approx.) Station Indicator must indicate a valid station 5.4.6 Mask Inserted into Focus For A2 to insert the Mask:



A1=extend A2=home E1=bottom

OK when A2=extend 5.4.7 Mask Retracted onto Elevator For A2 to retract the Mask: A1=extend A2=extend E1=bottom

OK when A2=home 6. System Air, Power & Signal Requirements 6.1 Air 2 l/min at 6bar. This will be the maximum usage and is expected during and insertion or the mask from the carrier into to focus position. 6.2 Electrical Power Item Quantity Power Voltage Max Duty Cycle Nema 23 Stepper Motor 1 24 24/day, 8/hour Solenoid Valve for Pneu 2 .55W 24 24/day, 8/hour 6.3 Logic Item Quantity Resolution Vane Switch 5 20µm Cable Position Transducer 1 0.1mm Proximity Sensor–Reed switch, magnetically actuated 4 0.1mm Photomicrosensor 1 10µm Bar Code Reader 1



Slitmask Mechanism Parts List

Sub-Assembly Part Name Part Number/Drawing Number Quantity Type Supplier Material Mass/Item Price/Item Focus Focus Base/Guider Mount 1 M Aluminium 5.939 Focus Slit Guider 1 M Aluminium 0.105 Track Roller LFR 50/5 KDD-4 6 C* INA Steel 0.010 Roller Flexure Mount 2 M Aluminium Elevator Linear Bearing LPS-12-30 1 C* Servo Systems Steel 3.170 Nema 23 Stepper Motor PK266-03 1 C Oriental Motors Steel 0.700 Cable Possition Transducer LX-PA-15-10K 1 C UniMeasure Thermoplastic 0.085 $205 Carrier Bracket 1 M Aluminium 0.174 Carrier Slit Guider 1 M Aluminium 0.175 Rodless Cylinder DGP-8-135-P-A-B 1 C FESTO 0.196 $186 Proximity Sensor SME-8-K-24 2 C FESTO 0.050 $26 Pneumatic Center Support Mount MUP-8 4 C FESTO 0.008 Latch Arm 1 M Aluminium 0.000 Latch Body 1 M Aluminium 0.003 Latch Knife 1 M Steel 0.001 Latch Mount 1 M Aluminium 0.002 Latch Spring 1 C TBD Latch Pusher 1 M Aluminium 0.005 Limit Switch VN101503 5 C Cherry Plastic Bar Code Scanner VS-310 1 C Microscan 0.085 Bar Code Scanner Support 2 M Aluminium Magazine Magazine Mount 1 M Aluminium 0.513 Magazine Box 1 M Aluminium 0.836 Magazine Rails 80 M Aluminium 0.007 Ball Detent 85015A55 40 C McMaster Carr Stainless Steel Long Pneumatic Cylinder DSNU-20-250-PPV-A 1 C FESTO 0.393 Proximity Sensor SMEO-4-K-24-B 2 C FESTO 0.075 Pneumatic Cylinder Foot Mount HNB-20-2 1 C FESTO 0.220



Proximity Sensor Mount SMBR-20 2 C FESTO 0.001 Mask Mask 50 O Fiber 0.010 Mask Holder 50 M Aluminium 0.041 Mask Holder Rail 100 M Steel 0.004 16.402 M - Manufactured O - Optic C - Commercial off the Shelf C* - Commercial off the Shelf with Modifications

Waveplate Mechanism Specification


PFIS – Waveplate Mechanism

SPECIFICATION

SALT-3130AE-0006

VERSION 1.1 February 2002

1. 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. 1.4 2. 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



3. Functional Requirements 3.1 Schematic Diagram 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 45o in 0.2-2 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.

a

b c

d



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 4.2.1 Mass Estimate The Mechanism currently has a mass of 11.05kg. The current estimate breakdown is given in the parts list appendix. 4.2.2 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 4.3.1 Dimensions of Optics ½ Wave Plate ¼ Wave Plate ¼ Wave Plate Blanks Full Blank

110mm

110mm

65mm

110mm

24mm

12mm

12mm

12mm



4.3.2 Position of Optics The distance from the focal plane to the ½ wave plate is 92.25mm 4.4 Positional Tolerances 4.4.1 Wave Plates Location Tolerances: X & Y: 0.1mm Z: 0.1mm Tip/Tilt: 5 arcminutes 4.5 Drive Requirements 4.5.1 Maximum Heat and Power Output The Power and temperature requirements of the SALT Telescope as set out in SALT System Specification Section, 5.3.2.5 shall be adhered to. 4.5.2 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

Focal Plane

Gap: 34mm



5. Design 5.1 Layout 5.1.1 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



5.1.2 ½ Waveplate Sub-Assembly

Gear Side View Encoder Side View (cut views made in older model)

Base

Stepper Motor

Bearing

Lens Mount

½ Waveplate

Encoder Ring

Encoder Head

Detent Alignment Pin



5.1.3 ¼ Waveplate Sub-Assembly

5.1.4 Outer Structure

¼ Waveplate Blank

Double Blank

Lens Holder Lens Cup

Lens Retainer

Pinion

Gear

¼ Waveplate



5.1.5 Outer Assembly

5.2 Configuration Actuators

Using two actuators back to back, we are able to position the quarter wave plate sub-assembly in two discrete positions

Rail

Pneumatic Actuator Connector

Hard Point

Pneumatic Actuator

Adapter Kit

Slit for Pneumatic

Outer Box

Rail

Adjustable end stops Attach points to

guider mount



5.3 Rotation 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.

Encoder Stepper Motor

Detent

Gear

Pinion



5.3.1 Encoding 5.3.2 Active Detent

5.4 Motion Control 5.4.1 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-12-150-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. 5.4.2 Interlocks For rotation motion, the detent must be released QWP actuator 2 cannot extend unless the HWP actuator has been extended.

Linear Bearing

Detent

Pneumatic Actuator



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 2 3-30W 3V-24V 10%-50% Pneumatic Valve 3 0.55W 24V Change of Modes 6.2.1 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 6.3.1 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.



Sub-Assembly Part Name Part Number/Drawing Number Quantity Type Supplier Material Mass/Item Price/Item

Quarter Wave Plate QWP-Base 1 M Aluminium 1.915 QWP-Optic 1 O Optic 0.050 QWP-Glass 1 O Optic 0.140 QWP-DoubleBlank 1 O Optic 0.280 QWP-LensMount 1 M Aluminium 0.116 QWP Ball Bearing K08008XP0K 1 C KAYDON Steel 52100 0.110 QWP Lens Cup 1 M Aluminium QWP Lens Retainer 1 M Aluminium QWP-OuterRing 1 M Aluminium 0.014 QWP-InnerRing 1 M Aluminium 0.008 QWP-6" Gear F24A77-144 1 C* WM BERG Aluminium 0.170 QWP-11/4"Pinoin F24A77-30 1 C WM BERG Aluminium 0.013 Stepper Motor PMC35A3 1 C ORIENTAL MOTORS 0.100 $250 Rotary Disk Encoder Custom 1 C* Micro-E Glass Encoder Hub (111mm) 1 M Aluminium Encoder Read Head M3000 1 C* Micro-E Aluminium Encoder Read Head Mount 1 M Aluminium Thread in Detent Pneumatic EGZ-5-5 1 C FESTO Detent Guide Runner ND 1-25.12 1 C Schneeburger Steel Detent 1 M Aluminium 0.000 Detent Pin 1 M Hardened Steel Linear Bearing Runner MR0442-712-01 4 C PACIFIC BEARING Steel (DIN 17230)/ Plastic Mandrel 0.009 SliderShim 4 M Aluminium 0.002 QWP-Pusher 1 M Aluminium 0.006 Half Wave Plate HWP-Base 1 M Aluminium 0.550 HWP-Optic 1 O Optic 0.130 HWP-LensMount 1 M Aluminium 0.179 HWP Ball Bearing K012008XP0K 1 C KAYDON Steel 52100 0.160 HWP Lens Cup 1 M Aluminium HWP Lens Retainer 1 M Aluminium HWP-OuterRing 1 M Aluminium 0.019 HWP-InnerRing 1 M Aluminium 0.012 HWP-6" Gear F24A77-144 1 C* WM BERG Aluminium 0.170 HWP-11/4"Pinoin F24A77-30 1 C WM BERG Aluminium 0.013



Stepper Motor PMC35A3 1 C ORIENTAL MOTORS 0.100 $250 Rotary Disk Encoder Custom 1 C* Micro-E Glass Encoder Hub (90mm) 1 M Aluminium Encoder Read Head M3000 1 C* Micro-E Aluminium Encoder Read Head Mount 1 M Aluminium Thread in Detent Pneumatic EGZ-5-5 1 C FESTO Detent Guide Runner ND 1-25.12 1 C Schneeburger Steel Detent 1 M Aluminium 0.000 Detent Pin 1 M Hardened Steel Linear Bearing Runner MR0442-712-01 4 C PACIFIC BEARING Steel (DIN 17230)/ Plastic 0.009 SliderShim 4 M Aluminium 0.002 HWP-Pusher 1 M Aluminium 0.005 Outer Assembly OuterBox 1 M Aluminium 3.392 MountPlate 2 M Aluminium 0.361 PneumaticCylinder 150mm Stroke 156040 ADVU-12-150-A-P-A 3 C FESTO 0.225 ADVU-Adapter 161194 DPVU-12/16 1 C FESTO 0.022 QWP Rail MR0445-702-41,611mm 2 C PACIFIC BEARING Steel (DIN 17230) 0.135 HWP Rail MR0445-702-19,281mm 2 C PACIFIC BEARING Steel (DIN 17230) 0.062 PneumaticRail MR0445-702-27,401mm 1 C PACIFIC BEARING Steel (DIN 17230) 0.088 OuterSliderShim 2 M Aluminium 0.003 PneumaticHardpoint 1 M Aluminium 0.022

9.670 M - Manufactured O - Optic C - Commercial off the Shelf C* - Commercial off the Shelf with Modifications

Grating Mechanism Specification


PFIS – Grating Mechanism

SPECIFICATION

SALT-3130AE-0009

VERSION 1 23 October 2002

1. Scope 1.1 Identification This document covers the design of the Grating Mechanism for PFIS. In it are detailed the specifications, operating criteria and the design. 1.2 System Overview The Grating Mechanism is the mechanism that selects one of 6 Gratings from the grating magazine and positions it in the grating rotation holder near the pupil. It also enables the rotation of the grating to the required angle relative to the beam and the articulated camera. 1.3 Document Overview This document first details the functional (science) requirements, then the technical (physical) requirements and details the design of the mechanism and sub mechanisms. 2. Referenced Documents SALT-1000AS0007 SALT System Specification SALT-1000AA0030 SALT Safety Analysis SALT-3120AA0002 Grating and Filter Specification Document 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



3. Science Requirements 3.1 Schematic Diagram 3.2 Geometry Substrate Dimensions 170 x 250mm 10mm (2 substrates through thickness) Clear Aperture 155 x 237mm 6 Gratings 3.3 Speed into Position and Duty Cycle Time to change grating and rotate: <30 sec Max. No. of changes per day: 48 3.4 Positional Repeatability and Alignment During observation: Translations: Rotations about: X: machine tolerance X: 10 micron edge to edge Y: machine tolerance Y: less than flexure Z: machine tolerance Z: 20 arcseconds Repeatable: Translations: Rotations about: X: machine tolerance X: 30 micron edge to edge Y: machine tolerance Y: 40 micron top to bottom Z: machine tolerance Z: 30 arcseconds Concentricity of Z axis and articulation axis: machine tolerance

Camera Tube Rotation Stage

Magazine Selection Stage

Grating Insert Pneumatic



3.5 Operational Modes The mechanism must be able to select any one of 6 gratings and position it in the rotation holder. 4. Technical Requirements 4.1 Interfaces The rotation subassembly will be attached to the articulating camera just above the articulation bearing. The magazine and its related structure will be attached to the camera cradle. 4.2 Physical Characteristics 4.2.1 Mass Estimate The Mechanism currently has an estimated mass of 25.6kg (including gratings). The current estimate breakdown is given in the parts list appendix. 4.2.2 Materials used and Properties The baseline choice of material will be aluminium. Hardened steel will be used for indexing detents. 4.3 Geometric Requirements 4.3.1 Position of Mechanism and Envelope The Grating has a 25mm wide envelope between the etalons this width restriction extends 125mm above and below the optical axis. Outside of that there is more space available – as dictated by the etalons and articulation mechanism. 4.3.2 Dimensions of Grating The grating in its holder should be less than 25mm thick. The Holder should enable a once off alignment of the grating in the holder. 4.4 Positional Tolerances The positional tolerance of the optical elements is detailed in section 3. The other sub-systems will be positioned and aligned so as to allow smooth and unobstructed sliding of the grating holders between them. Typically the parts of the mechanism will be aligned to within 100µm of each other.



4.5 Drive Requirements 4.5.1 Maximum Heat and Power Output The Power and temperature requirements of the SALT Telescope as set out in SALT System Specification Section, 5.3.2.5 shall be adhered to. 4.5.2 Encoding All motor driven stages will have absolute or incremental with and index encoding over their full range while pneumatic actuators will only have position sensors at their end positions. The motor drive stage will have encoding and soft limits used for positioning while hard limit switches will stop the stage from going outside of its operating range. The Rotation stage will have full range quadrature encoding 4.6 Safety All mechanisms shall be designed such that electrical or software malfunctions cannot damage any hardware. Pneumatics should hold their position during a power failure and solenoids should fail in a clamped position



5. Description of Design 5.1 Layout Above are shown the four main subassemblies of the Grating mechanism. 5.1.1 Grating and Holder

Rotation Sub-Assembly

Grating and Holder

Structure

Magazine Selector Sub-Assembly

Teflon Sheet

Groove for detent Knife

Y-Rotation Stop

Guide and X, Z Positioner

Insertion / Slide Rail

Z

Y

X



The Grating holder is designed to be both a mount for the grating and to facilitate accurate, repeatable positioning of the gratings in the grating rotator. The mount is designed to allow adjustment of the grating. Four, once off machined mount pads in the four corners of the mount allow adjustment of X position and rotation about Y. Nylon tipped set screws position the grating in Y, Z and rotations about X.(Still to be detailed) The holder is designed to come reproducibly to the same place in the rotation stage by setting against the following hard points (as the pneumatic inserts the grating) : The grove on the one guide rod is designed to mate with a knife type detent on the stage holding the grating to a position in X,Y and Z, The other guide rod sets the grating in X and Z but allows for movement in X. The Y rotation is constrained by an index tooth protruding from the bottom of the holder indexing against a hard stop, driven against it by a sprung ball. 5.1.2 Rotation Subassembly The rotation holder facilitates the positioning of the grating described above by providing the 3 kinematic points required for positioning. The rotation stage itself is an off the shelf rotation stage which can rotate the work piece to 20 arc/sec accuracy. The rotation encoder is a rear shaft mounted optical encoder used to verify the rotation position.

Y-Rotation Stop Ball-Detent

Rotation Stage

X,Z Restraint

XYZ Restraint (Knife Detent)

Rotation Encoder



5.1.3 Magazine Selector Sub Assembly The magazine slides on to circular rails on open linear ball bearings. The Grating holders are each mounted to a slide which runs along a rail on the magazine structure. The rail has a gap for one grating at the insertion pneumatic where an independent section of rail holds the grating to insert it. The rail is held by a construction ball which accurately positions it in the magazine, but when pressing down in the rotation stage it does not over constrain the grating.



The magazine box holds the six gratings separate and keeps them parallel when sliding on the rail. 5.1.4 Structure The Base of the structure mounts to the camera tube cradle. The rails for the magazine and for the gratings within the magazine are mounted to the structure.



5.2 Speed of Motion The pneumatic actuators will undergo their full range of motion in less than 4 seconds. The linear stage has a ball screw with a lead of 4mm. The maximum speed of the motor (directly coupled) is 400 rev/min (which would provide the 16 oz-in of torque which would be required to slide the 15 kg magazine). The travel Required is 150mm so 37rev required. Stacked together the motions would take a maximum of 24 seconds the encoding time must thus be of the order of 6 seconds to ensure a grating changeover in less than 30 seconds. Linear Slide Motor Torque – speed data

De-rotate Grating (4s)

Remove Grating (4s)

Rotate Grating to New angle (4s)

Magazine Move -Select New Grating (8s)

Inset Grating (4s)

(PK545 Motor)



5.3 Motion Control 5.3.1 Select a Magazine Position for Required Grating Motion: This Motion is achieved using a linear stage powered by stepper motor (S.10.1). Encoding: There are vane limit switches (S.10.1-B.1 & S.10.1-B.2) at the ends of travel. The end of travel switch is used to index the cable transducer. A cable transducer (S.10.1-E.1) provides absolute encoding over the full range of travel ant this together with step counting is used to position the stage. There is a station indicator (S.10.1-B.3) which tells the stage that it is in a valid grating position. 5.3.2 Grating Insertion Motion: The insertion of the grating is driven by a pneumatic cylinder (P.10.1). Encoding: The end positions of the cylinder are encoded with proximity switches (P.10.1-B.1 & P.10.1-B.2) 5.3.3 Grating Rotation Motion: Rotation is achieved by an off the shelf rotation stage driven by a stepper motor (S.10.2) Encoding: Encoding of the rotation is achieved by a shaft encoder off a back shaft of the rotation stage (S.10.2-E.1). There is a home indicator to indicate that the grating is perpendicular to the optical axis of the camera (S.10.2-B.1) and well as end of travel switches.



5.4 Control Interlocks For the normal modes of operation to be executed, the following conditions must be met: 5.4.1 To move the magazine to select a grating For S.10.1 to move P.10.1-B1= on (pneumatic pulled in)

OK when S.10.1-B.3 = valid (magazine at a valid station) and S.10.1-E.1 is at correct value for desired grating.

5.4.2 To insert a grating For P10.1 to insert a grating: S.10.2-B.1 = home (rotator perpendicular to camera) S.10.1-B.3 = valid (magazine at a valid station)

OK when P.10.1-B2= on (pneumatic extended) 5.4.3 To return a grating For P10.1 to remove a grating: S.10.2-B.1 = home (rotator perpendicular to camera) S.10.1-B.3 = valid (magazine at a valid station)

OK when P.10.1-B1= on (pneumatic pulled in) 5.4.4 To Rotate a grating For S.10.2 to rotate: P.10.1-B2= on (pneumatic fully extended) OK when S.10.2-E.1 indicates required angle 6. System Air, Power & Signal Requirements

Camera Tube Rotation Stage (S.10.2)

Magazine Selection Stage (S.10.1)

Grating Insert Pneumatic (P.10.1)



6.1 Air 2 l/min at 6bar. This will be the maximum usage and is expected during and insertion or the mask from the carrier into to focus position. 6.2 Electrical Power Item Quantity Power Voltage Max Duty Cycle Stepper Motor (S.10.1) 1 1.5 A/phase 24 48/day, 16/hour Stepper Motor (S.10.2) 1 24 48/day, 16/hour Solenoid Valve for Pneu 1 .55W 24 48/day, 16/hour 6.3 Logic Item Quantity Resolution Vane Limit Switch 6 20µm Cable Position Transducer 1 0.1mm Proximity Sensor–Reed switch, magnetically actuated 2 0.1mm Photomicrosensor 1 10µm The ‘at a station’ indicator switch and the narrow at home switch will be achieved using two vane type hall sensors in an exclusive or arrangement to ensure narrow acceptable ranges.



SubAssembly Part Name Quantity Part Number Man/COTS Manufacturer Material Unit Mass Total Mass

Rotation Stage Rotation Holder 1 M Aluminium 0.01 0.01 Rotation Stage Knife Detent 1 M Steel 0.00 0.003 Rotation Stage Rotation Mount 1 M Aluminium 0.27 0.27 Magazine Assembly Magazine 1 M Aluminium 2.42 2.42 Magazine Assembly Linear Open Bearing 4 AG-OPAJ-12-KS C American Metric Corp Aluminium 0.11 0.44 Magazine Assembly Tee 38x38x2x43 4 M Aluminium 0.02 0.08 Magazine Contents Grating 1400 (175X230X20) 1 O BK7 2.02 2.02 Magazine Contents Grating 1800 (175X250X20) 1 O BK7 2.20 2.2 Magazine Contents Grating 2300 (175X250X20) 1 O Fused Silica 1.93 1.93 Magazine Contents Grating 3150 (175X250X20) 1 O Fused Silica 1.93 1.93 Magazine Contents Grating Transmission 1 O Optic 1.68 1.675 Grating Frame Proximity Sensor SMEO 2 SMEO-4-K-LED-24-B C FESTO Plastic 0.01 0.01 Grating Frame Proximity Sensor Mount 2 SMBR-20 C FESTO 0.00 0.002 Grating Structure Beam 1 2 M Aluminium 0.67 1.34 Grating Structure Beam 2 2 M Aluminium 0.50 1 Grating Structure Beam 3 2 M Aluminium 0.21 0.42 Grating Structure Beam 4 2 M Aluminium 0.04 0.08 Grating Structure Beam 5 1 M Aluminium 0.24 0.24 Grating Structure UP Beam 2 M Aluminium 0.54 1.08 Grating Structure Main Beam 2 M Aluminium 0.60 1.2 Grating Structure Cross Beam 4 M Aluminium 0.11 0.44 Grating Structure Cross Beam Long 1 M Aluminium 0.21 0.21 Grating Structure Long Rail Support 1 M Aluminium 0.07 0.07 Grating Structure Short Rail Support 1 M Aluminium 0.05 0.05 Magazine Contents Grating Holder 1 M Aluminium 0.63 0.63 Magazine Contents Carriage 1 MR7 C Pacific Bearing Steel 0.02 0.02 Magazine Contents Self Adhesive Teflon Sheet 0.8thk 12 C* InterPlast Teflon 0.00 0.048 Magazine Contents Grating 900 (175X200X20) 1 O Fused Silica 1.54 1.54 Pneumatic Short Rail 1 MR7 (24) C Pacific Bearing Steel 0.01 0.007 Pneumatic Construction Ball 1 C McMaster Aluminium 0.00 0.001 Sliding Sum Assembly Long Rail 2 MR7 (155) C Pacific Bearing Steel 0.04 0.08 Grating Frame Pneumatic Cylinder 1 DSNU-20-250-PPV-A C FESTO 0.39 0.393 Grating Frame Rail - Shaft 2 WV-12 (375) C American Metric Corp Steel 0.33 0.666 Grating Frame Linear Table Stage 1 TU 40C 18 A/K3BG4S02RQ C IKO Aluminium 1.30 1.3 Grating Frame Pneumatic Cylinder Flange Mount 1 FBN-20/25 C FESTO Steel 0.05 0.045



Grating Frame Stage Front Mount 1 M Aluminium 0.03 0.03 Grating Frame Stage Back Mount 1 M Aluminium 0.04 0.035 Grating Frame Pneumatic Mount Block 2 M Aluminium 0.07 0.14 Grating Frame Carrier Block 1 M Aluminium 0.06 0.06 Grating Frame Vane Hall Switch 5 VN101503 C Cherry Plastic 0.01 0.025 RotationStage Rotation Stage 1 PI M-038.2S C Physic Instrument Aluminium 1.25 1.25 RotationStage Ball-Nose Spring Plunger 1 3408A98 C McMaster Stainless Steel 0.00 0.003 Grating Frame Cable Possition Transducer 1 LX-PA-15-10K C UniMeasure Thermoplastic 0.09 0.085 Grating Frame Vane Hall Switch 4 VN101503 C Cherry Plastic 0.01 0.02 25.498

Beam Splitter Mechanism Specification


PFIS – Beam Splitter Mechanism

SPECIFICATION SALT-3130AE-00010

VERSION 1.0

16 February 2003

1. Scope 1.1 Identification This document covers the design of the Beam Splitter Mechanism for PFIS. In it are detailed the specifications, operating criteria and details of the design. 1.2 System Overview The Beam Splitter Mechanism is the mechanism that inserts and removes the beam splitter from the beam. 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. 2. 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



3. Science Requirements 3.1 Schematic Diagram 3.2 Geometry The individual beam splitter prisms have the following geometry. The mechanism comprises a 3x3 array of back-to-back prisms – ie18 prisms in total. See SALT-3120AA0003.

3.3 Speed into Position and Duty Cycle Time to insert beam splitter ~5 seconds No. of insertion/removes per evening: ~8

Optical Axis

Beam Splitter

Camera Tube Dewar

Insert Remove Beam Splitter



3.4 Positional Repeatability and Alignment Location Tolerances: X & Y: 0.1mm Z: 0.1mm Tip/Tilt: 5 arcminutes Rotation about the optical axis: 3arcminutes 3.5 Operational Modes The Beam Splitter is either in or out of the beam 4. Technical Requirements 4.1 Interfaces The beam splitter is located just after the second etalon and just before the camera. The in beam parts of the mechanism will be attached to the camera front flange and the actuator will be attached to the structure of the grating mechanism. 4.2 Physical Characteristics Mass Estimate The Mechanism currently has an estimated mass of 4.425KG. The current estimate breakdown is given in the parts list appendix. Materials used and Properties The baseline choice of material for this mechanism will be aluminium. 4.3 Geometric Requirements The beam splitter mechanism has an 18mm envelope in which it has to slide. It is free to move out of the beam in an up (+z) direction 4.4 Positional Tolerances The positional tolerance of the optical elements is detailed in section 3. The articulation mechanism will provide repeatable positioning of the camera to 15 microns.



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, 5.3.2.5 shall be adhered to. Encoding All motor driven stages will have absolute encoding while pneumatic actuators will only have position sensors at their end positions. The motor drive stage will have encoding and soft limits used for positioning while hard limit switches will stop the stage from going outside of its operating range. The articulation mechanism will have full range quadrature encoding with an accuracy of 15microns. 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.



5. Description of Design 5.1 Layout Basic Overall Layout

Prism Holder

Prism Holder

Slide Rails

Camera Tube

Camera Front Flange

Pneumatic Actuator

Fastening Rings

Back to back stack of 2 Prisms

Slides



5.2 Speed of Motion The pneumatic actuator will undergo its full range of motion in less than 4 seconds. 5.3 Motion Control Motion Motion in and out of the beam is by means of a pneumatic actuator (FESTO DSNU-20-250-PPV-A). The actuator is controlled by a micro-pneumatic valve (FESTO MZH-5/3-M3-L). Encoding There are proximity sensors (SMEO-4-K-24-B) at the home and extended position of the actuator.

Remove beam splitter (4s)



5.4 Control Interlocks 6. System Air, Power & Signal Requirements 6.1 Air 2 l/min at 6bar. This will be the maximum usage and is expected during and insertion of beam splitter. 6.2 Electrical Power Item Quantity Power Voltage Max Duty Cycle Solenoid Valve for Pneu 1 .55W 24 24/day, 8/hour 6.3 6.4 Logic Item Quantity Resolution Proximity Sensor–Reed switch, magnetically actuated 2 0.1mm


SALT-3130AE-00010 8

Part Name Quantity Part Number Man/COTS Manufacturer Material Unit MassTotal Mass

HWP-Slider_Mounting_Plate 4 M Aluminium 0.01 0.04 Star - Miniature Ball Rail System Runner Blocks 4 MR0442-712-01 C Rexroth Bosch Group (Star) Steel (DIN 17230)/ Plastic 0.01 0.036 Star - Miniature Ball Rail System Guid Rail 2 MR0445-702-31 C Rexroth Bosch Group (Star) Steel (DIN 17230) 0.22 0.44 Pneumatic Cylinder 1 DSNU-20-250-PPV-A C FESTO 0.39 0.393 Pneumatic Cylinder Flange Mount 1 FBN-20/25 C FESTO Steel 0.05 0.045 Proximity Sensor SMEO 2 SMEO-4-K-LED-24-B C FESTO Plastic 0.01 0.01 Proximity Sensor Mount 2 SMBR-20 C FESTO 0.00 0.002 Beam Splitter Prism 19 M Aluminium 0.05 0.95 Prism Holder 1 M Aluminium 1.05 1.05 RingRetainerPad 16 M Aluminium 0.01 0.08 Star - Miniature Ball Rail System Runner Blocks 4 MR0442-712-01 C Rexroth Bosch Group (Star) Steel (DIN 17230)/ Plastic 0.01 0.036 Star - Miniature Ball Rail System Guid Rail 2 MR0445-702-31 C Rexroth Bosch Group (Star) Steel (DIN 17230) 0.22 0.44 Camera Front Flange 1 M Aluminium 0.50 0.5 Pneumatic Cylinder 1 DSNU-20-250-PPV-A C FESTO 0.39 0.393 Proximity Sensor SMEO 2 SMEO-4-K-LED-24-B C FESTO Plastic 0.01 0.01 4.425

Filter Mechanism Specification


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, operating criteria and design. 1.2 System Overview The Filter Mechanism is the mechanism that selects one of 20 filters from the Filter Magazine and inserts it into the beam. 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. 1.4 Referenced Documents SALT-1000AS0007 SALT System Specification SALT-1000AA0030 SALT Safety Analysis SALT-3120AA0002 Grating and Filter Specification Document 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



2. Science Requirements 2.1 Schematic Diagram 2.2 Geometry Maximum Filter Size 2.3 Speed into Position and Duty Cycle Time to change filter ~20 seconds No. of angle changes per evening: ~20

Optical Axis

Filter In Position

Magazine 20 Filters

Camera Tube Dewar

8mm 130mm

90mm



2.4 Positional Repeatability and Alignment X-Y placement: 60 microns repeatable 15 microns during observation (Z-placement has no discernable effect on image quality) Tip-tilt: 6.0 arcmin repeatable (150 micron end to end) 1.5 arcmin during observation (50 micron end to end) Note: X is short dimension, Y is long dimension, and Z is along the optic axis of the camera. 2.5 Operational Modes The mechanism must be able to select any of 20 filters and place it in the beam. The filter magazine invades the PFIS 3000mm diameter envelope for 5 filters while the camera is at the unarticulated position. The 5 inner-most filters in the magazine must thus be chosen to be the ones used at highest articulation angle. 3. Technical Requirements 3.1 Interfaces The filter mechanism is attached to the articulation frame structure along side the camera tube. The magazine must remain at least 152mm from the optical axis so as to be outside of the camera. The dewar envelope is smaller than the camera tube in diameter. The gap between the last camera element and the dewar field lens is 27mm and the filter and all it’s in-situ mechanism need to be within this envelope. 3.2 Physical Characteristics 3.2.1 Mass Estimate The Mechanism currently has an estimated mass of 15.84kg (including filters). The current estimate breakdown is given in the parts list appendix. 3.2.2 Materials used and Properties



The baseline choice of material for this mechanism will be aluminium. The magnets mode from Alnico 5. The sliding surfaces on the aluminium magazine will be given a low friction coating. All surfaces will be black anodised. 3.3 Positional Tolerances The positional tolerance of the optical elements is detailed in section 3. The articulation mechanism will provide repeatable positioning of the camera to 15 microns. 3.4 Drive Requirements 3.4.1 Maximum Heat and Power Output The Power and temperature requirements of the SALT Telescope as set out in SALT System Specification Section, 5.3.2.5 shall be adhered to. 3.4.2 Encoding All motor driven stages will have absolute encoding while pneumatic actuators will only have position sensors at their end positions. The motor drive stage will have encoding and soft limits used for positioning while hard limit switches will stop the stage from going outside of its operating range. The articulation mechanism will have full range quadrature encoding with an accuracy of 15 microns. 3.5 Safety All mechanisms shall be designed such that electrical or software malfunctions cannot damage any hardware. Pneumatics should hold their position during a power failure and solenoids should fail in a clamped position



4. Description of Design 4.1 Layout 4.1.1 Basic Overall Layout The in position assembly is mounted to the camera tube flange. The Stage is mounted to the articulation mechanism structure and the magazine is fixed to the stage.

Magazine

Stage

Camera Tube

In Position Assembly

Stationary Face Plate

Sliding Face Plate



4.1.2 Filter Magazine Back View

Filter Rails

Steel Strip for Magnet attachment

Filter Sliding Face Plate Stop

Removable section for access to filter engagement Mount Holes

Stationary Face Plate angle



4.1.3 Face Plates 4.1.4 Since the magazine protrudes form the instrument envelope when accessing the furthest in filters, the face plate needs to move with the magazine so that it does not remain outside of the envelope. (this is all done so that we can get 5 extra filters into the magazine. – we use the fact that when articulated the filter magazine is pulled back of the envelope) The sliding face plate is pushed out with the magazine and then returns (attached to it with a magnet). When the sliding face plate gets in far enough, it strikes the back stop and stays attached to that with a magnet. (this is since the face plate cannot slide across the filter insertion slot).

Stationary Face Plate (mounted to camera tube)

Sliding Face Plate

Magnets

Back Stop

Front Stop Sliding Channel Rail

Filter Insertion slot



4.1.5 Stage 4.1.6 In Position Assembly

Stepper Motor Position Transducer

Stage

Vane Switch Mount Bracket

Flexure Mount

Bar Code Reader

Insertion Pneumatic

Rollers

Adjustable End Stop



4.2 Speed of Motion The pneumatic actuators will undergo their full range of motion in less than 4 seconds. The linear stage has a lead screw with 16 threads per inch. The maximum speed of the motor (directly coupled) is 2000 rev/min. Twice the full travel of the linear stage – 300mm, would require 200 revolutions which would take 6 seconds, running the motor at 75% of top speed would still enable full motion in 9 sec. Stacked together the motions would take a maximum of 17 seconds. Allowing 3s for the encoding keeps us within the allowed 20s. 4.3 Motion Control 4.3.1 Stage Motion to Align magazine for required filter Motion The stage motion is by means of a Stepper Motor (Oriental Motors PK266-03) driving a worm screw on a linear stage. Encoding There is a Linear Cable Transducer (UniMeasure LX-PA-10k) which gives full range absolute encoding. On the elevator are vane limit switches at the extents of travel. There is an ‘at a station’ indicators which comprise two vane switches along side each other and 2 metal vaned strip with teeth at the station spacing. By off-setting vaned strips slightly we create a narrow band station indicator. The ‘at a station’ indicator switch and the narrow at home switch will be achieved using two vane type hall sensors in an exclusive or arrangement to ensure narrow acceptable ranges.

Remove Filter from beam (4s)

Select New Filter (9s)

Insert Filter (4s)


Doc No. SALT-3130AE-00012 10

4.3.2 Slide Mask between Magazine and Focus Motion Motion in and out of Beam from the magazine is by means of a pneumatic actuator (FESTO DSNU-20-250-PPV-A). The actuator is controlled by a micro-pneumatic valve. Encoding There are proximity sensors (SMEO-4-K-24-B) at the home and extended position of the actuator. 4.4 Control Interlocks For the normal modes of operation to be executed, the following conditions must be met: 4.4.1 Magazine to select an new filter The Pneumatic must be fully extended 4.4.2 To pull a filter into the beam (or return it to the magazine) The Magazine must be at a valid station 5. System Air, Power & Signal Requirements 5.1 Air 2 l/min at 6bar. This will be the maximum usage and is expected during and insertion or the mask from the carrier into to focus position. 5.2 Electrical Power Item Quantity Power Voltage Max Duty Cycle Nema 23 Stepper Motor 1 24 24/day, 8/hour Solenoid Valve for Pneu 1 .55W 24 24/day, 8/hour 5.3 5.4 Logic Item Quantity Resolution Vane Switch 4 20µm Cable Position Transducer 1 0.1mm Proximity Sensor–Reed switch, magnetically actuated 2 0.1mm Bar Code Reader 1


SALT-3130AE-00012 11

Mechanism SubAssembly Part Name Quantity Part Number Man/COTS Manufacturer Material Unit MassTotal Mass

Filter FilterAssembly Filter 20 O Optic 0.20 4 Filter FilterAssembly Filter Holder Magnet 40 5K241 C Group Arnold Alnico 5 0.01 0.2 Filter FilterAssembly FilterHolder 20 M Aluminium 0.03 0.6 Filter FilterAssembly FilterHolderRail 40 M Aluminium 0.03 1.28 Filter InPossitionAssembly Bar Code Scanner 1 MS-3 CCD C Microscan 0.09 0.085 Filter InPossitionAssembly Bracket Bump Stop 1 M Aluminium 0.00 0.003 Filter InPossitionAssembly CameraFlange 1 M Aluminium 1.40 1.396 Filter InPossitionAssembly InSlotPusher 1 M Aluminium 0.01 0.01 Filter InPossitionAssembly Pneumatic Cylinder 1 DSNU-20-250-PPV-A C FESTO 0.39 0.393 Filter InPossitionAssembly Proximity Sensor Mount 2 SMBR-20 C FESTO 0.00 0.002 Filter InPossitionAssembly Proximity Sensor SMEO 2 SMEO-4-K-LED-24-B C FESTO Plastic 0.01 0.01 Filter InPossitionAssembly RollerFlexureMount (Filter) 2 M Aluminium 0.03 0.066 Filter InPossitionAssembly Standoff Roller In Position 1 M Aluminium 0.00 0.003 Filter InPossitionAssembly Track Roller (Filter) 6 LFR 5201 KDD C INA Stainless Steel 0.01 0.06 Filter Magazine Alnico 5 Button Magnet 4 MC5688K51 C McMaster Alnico 5 0.01 0.04 Filter Magazine Alnico 5 Front Bracket 2 M Aluminium 0.01 0.01 Filter Magazine Alnico Front Magnet Stop 2 M Aluminium 0.01 0.01 Filter Magazine Alnico Magnet Stop 2 M Aluminium 0.01 0.01 Filter Magazine Alnico Magnet Stop Bracket 2 M Aluminium 0.01 0.01 Filter Magazine Filter Magnet Strip 2 M Aluminium 0.13 0.262234 Filter Magazine Magazine Filter Bottom 1 M Aluminium 0.30 0.3 Filter Magazine Magazine Filter Front 1 M Aluminium 0.12 0.12 Filter Magazine Magazine Filter Rear 1 M Aluminium 0.12 0.12 Filter Magazine Magazine Filter Slide Plate 1 M Aluminium 0.77 0.77 Filter Magazine Magazine Front Angle 1 M Aluminium 0.02 0.02 Filter Magazine Magazine Slide Angle 1 M Aluminium 0.03 0.034 Filter Magazine Sliding Channel Teflon Tape 4 C Teflon 0.00 0.004 Filter Magazine Sliding Plate Magnet Bracket 2 M Aluminium 0.01 0.01 Filter Magazine Sliding Plate Magnet Bracket 2 M Aluminium 0.01 0.01 Filter Magazine SlidingFacePlate 1 M Aluminium 0.17 0.17 Filter Magazine SlidingFacePlate Channel 2 M Aluminium 0.06 0.12 Filter Magazine Stationary Face Plate Mount 1 M Aluminium 0.04 0.036 Filter Magazine Stationary Magnet Stop Mount 2 M Aluminium 0.01 0.01 Filter Magazine StationaryFacePlate 1 M Aluminium 0.23 0.23 Filter Stage Cable Possition Transducer 1 LX-PA-15-10K C UniMeasure Thermoplastic 0.09 0.085


SALT-3130AE-00012 12

Filter Stage Linear Bearing 1 LPS-12-30 C* Servo Systems Steel 3.17 3.17 Filter Stage Magazine Mount (Filter) 1 M Aluminium 0.85 0.85 Filter Stage Nema 23 Stepper Motor 1 PK266-02 C Oriental Motors Steel 0.70 0.7 Filter Stage Stage Mount 1 M Aluminium 0.59 0.588 Filter Stage Vane Hall Switch 5 VN101503 C Cherry Plastic 0.01 0.025 Filter Stage Vane Hall Switch 4 VN101503 C Cherry Plastic 0.01 0.02 15.84223

Articulation Mechanism Specification


PFIS – Articulation Mechanism

SPECIFICATION

SALT-3130AE-0013

VERSION 1 16 February 2003

1. Scope 1.1 Identification This document covers the design of the Articulation Mechanism for PFIS. In it are detailed the specifications, operating criteria and details of the design. 1.2 System Overview The Articulation Mechanism is the mechanism that articulates the camera from 0 to 100 degrees during grating spectroscopy mode operations. 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. 2. Referenced Documents SALT-1000AS0007 SALT System Specification SALT-1000AA0030 SALT Safety Analysis SALT-3120AA0002 Grating and Filter Specification Document 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



3. Science Requirements 3.1 Schematic Diagram 3.2 Geometry The geometry of the camera is assumed to be a 300mm ID tube (304mm OD), 550mm long. The articulation Axis is at (–535,0) and the camera is 200mm from the articulation axis. 3.3 Speed into Position and Duty Cycle Time to rotate 100 degrees: ~20 seconds Time to clamp and unclamp: ~2 seconds No. of angle changes per evening: ~20

535mm 205mm 558mm

304mm



3.4 Positional Repeatability and Alignment The accuracy of positioning of the front and back of the camera are as follows: During observation: Translations: X,Y,Z: 5 micron Repeatable Positioning: Translations: X,Y,Z: 15 micron Absolute Position: Translations: X,Y,Z: 100 micron Concentricity of Z axis and grating rotation axis: machine tolerance (100 microns) 3.5 Operational Modes The mechanism must be able to articulate the camera to discreet positions, 0.5 degrees apart between 0 and 100 degrees of articulation. 4. Technical Requirements 4.1 Interfaces The articulation bearing is attached to the PFIS structure on the same axis as the grating rotation axis. The grating rotation mechanism is attached just above the articulation bearing. The grating frame is attached to the articulation frame on the sides of the camera. The PFIS camera is cradled in the articulation frame. The filter mechanism is attached to the articulation frame 4.2 Physical Characteristics 4.2.1 Mass Estimate The Mechanism currently has an estimated mass of 17.1kg. The current estimate breakdown is given in the parts list appendix. 4.2.2 Materials used and Properties The baseline choice of material will be aluminium. The detent strip will be made of invar as it is directly attached to the I-beam on the PFIS structure.



4.3 Geometric Requirements 4.3.1 Position of Mechanism and Envelope The articulation bearing axis is along the z-axis at x=-535, y = 0. The cam rollers run on the I-beam, at a radius of 650mm. The articulation mechanism cradles the 304mm OD camera tube, 7mm off center (away from the direction of rotation). The mechanism must be able to rotate from 0 through to 100 degrees. 4.4 Positional Tolerances The positional tolerance of the optical elements is detailed in section 3. The articulation mechanism will provide repeatable positioning of the camera to 15 microns. The absolute positioning – as a result of I-beam flatness and bearing concentricity will be to 100 microns. 4.5 Drive Requirements 4.5.1 Maximum Heat and Power Output The Power and temperature requirements of the SALT Telescope as set out in SALT System Specification Section, 5.3.2.5 shall be adhered to. 4.5.2 Encoding All motor driven stages will have absolute encoding while pneumatic actuators will only have position sensors at their end positions. The motor drive stage will have encoding and soft limits used for positioning while hard limit switches will stop the stage from going outside of its operating range. The articulation mechanism will have full range quadrature encoding with an accuracy of 15microns. 4.6 Safety All mechanisms shall be designed such that electrical or software malfunctions cannot damage any hardware. Pneumatics should hold their position during a power failure and solenoids should fail in a clamped position



5. Description of Design 5.1 Layout 5.1.1 Basic Overall Layout The drive and detent sub-assemblies are mounted off one of the cradle beams of the articulation mechanism.

Articulation Bearing Drive Sub-Assembly

Camera

Camera Cradle Beams

Articulation Rail

Detent Sub assembly

Detent Rail Flexible Gear Rack



5.1.2 Drive and Detent Drive Assembly

Detent Sub assembly

Drive Sub Assembly

Mount Plate welded to Structure

Fail Safe Brake

High-Torque Stepper Motor

Gear Box Pinion Gear Flexible Rack

Welded to Angle section



Detent Assembly 5.1.3 Bearing and Cam Roller Cam Rollers

Detent Rail (1 of 200 cut-outs shown)

Detent Pneumatic Actuator

Compression Spring

Precision Slide

Pneumatic Push-off Structure

7.5 Degree Mount Wedge

Cam Roller

Encoder

Encoder Tape Tensioner



Articulation Bearing 5.2 Speed of Motion The motor has a rated speed of 10 rps at 1.06 Nm torque. The torque out of the 16:1 gearbox is thus ~13.6Nm. At a cruise speed of ~10rps, the camera will be able to move its full range of travel in 20s

Release Detent (1s)

Insert Detent (1s)

Release Brake (1s)

Apply Brake (1s)

Rotate 100 Degrees (20s) Power Windings Off (1s)

Power Windings (1s)

Shaft – attached to Structure

Bearing Housing

Bearing Pressure Plate

Bearing Set



5.3 Motion Control 5.3.1 Articulation Rotation Motion The stepper motor (KM063F13) provides the motion by means of a 16:1 gear box rotating a pinion gear onto a rack mounted on the inside of the articulation rail. This drive system is low precision and is designed to get the camera to within 0.5mm of a detent position. A pneumatic driven detent (ADVU-63-10-A-P-A) provides precise positioning by driving a wedge detent into the detent rail on the inside of articulation rail. The detent positions the camera to 15 micron repeatability at one of the 200 articulation positions (every 0.5 degrees). Encoding An angle encoder provides angular encoding of the articulation to 3.5 arc seconds precision. This encoder has a built in index mark. The detent inserted position is registered by a position sensor (SME-8-K-LED-24). 5.4 Control Interlocks In order to allow the detent to position the camera (with the motor off) while ensuring that the camera is always under control, the following series of interlocked actions need to be adhered to. Detent There are three allowed detent states.

1) Free when the detent is out and the camera is free to articulate. 2) Caught, when the detent is inserted far enough to prevent articulation but is not

yet fully inserted 3) Positioned, when the detent is fully nested in its slot and the camera is at its final

precise position. Motor Then the motor which drives the motion has three allowable states.

1) Rotate

S1 S2 S3 S1 S2 S3 S1 S2 S3

Free Positioned Caught



2) Holds (with windings on) 3) Free (windings off)

Brake The brake can be either on or off, it is a fail-safe brake and thus requires power to be released. We thus want it clamping whenever we are not trying to move the articulation mechanism so as to minimize heat dissipation. Order of events in normal operation This is the order of events to operate the articulation mechanism – move from one articulation angle to another. At rest the mechanism will have the detent positioned, the motor free and the brake clamped

1) Power windings 2) Release brake 3) Retract detent (wait for signal from sensor S1) 4) Rotate motor till camera is within 0.5mm of required position 5) Insert detent (wait for signal from sensor S2) 6) Turn motor windings off. (wait for signal S3) 7) Clamp Brake

Additionally there is an interlock to the Etalon Mechanism to ensure that the camera does not articulate while the Etalons are inserted 6. System Air, Power & Signal Requirements 6.1 Air The maximum air usage for the 1second it takes to insert the detent would be 2 l/min at 6bar. 6.2 Electrical Power Item Quantity Power Voltage Max Duty Cycle Nema 23 Stepper Motor 1 3.5A 24 24/day, 8/hour Fail Safe Brake 1 .25A 24 24/day, 8/hour Solenoid Valve for Pneu 1 .55W 24 24/day, 8/hour 6.3 Logic Item Quantity Resolution Vane Switch 3 10µm Angle Encoder 1 10µm Proximity Sensor–Reed switch, magnetically actuated 3 0.1mm



SubAssembly Part Name Quantity Part Number Man/COTS Manufacturer Material Unit Mass Total Mass DetentSubAssembly Detent Stage Wedge 1 M Aluminium 0.40 0.4 3/4 Angle Brace 1 M Aluminium 0.10 0.1 3/4 Angle Brace Bottom 1 M Aluminium 0.10 0.1 Pneumatic Pusher Brace 1 M Aluminium 0.30 0.3 Festo Compact Cylinder 1 ADVU-63-10-A-P-A C FESTO 0.75 0.745 Detent Rail 1 M Invar 1.50 1.5 Pneumatic-DetentPlate 1 M Steel 0.20 0.196 TableNK3-180 1 NK3-180 C Schneeberger 1.72 1.72 ArticulationDetent 1 M Steel 0.05 0.05 Proximity Sensor SME 3 SME-8-K-LED-24 C FESTO 0.05 0.15 DriveSubAssembly Gearbox 1 023RCX0160 C CGI, INC Steel 1.27 1.27 Flexible Rack 1 FCRP5-2000 C Quality Transmission Components SS400 0.30 0.3 Rack Angle Mount 1 M Steel 0.50 0.5 Motor Mount 1 M Aluminium 0.15 0.15 Failsafe Brake 1 MFSB-7-4 C Electroid Steel 0.27 0.27 Encoder Bracket 1 M Aluminium 0.02 0.02 Angle Encoder 1 ERA 881 C C HeidenHain Plastic 0.35 0.35 Vane Hall Switch 3 VN101503 C Cherry Plastic 0.01 0.015 High Torque SloSyn Motor 1 KM063F13 C SloSyn Steel 1.45 1.45 Frame Motor/DetentMount 1 M Aluminium 1.00 1 Bearing Housing 1 M Aluminium 1.03 1.03 Bearing Retainer 1 M Aluminium 0.03 0.0319 Articulation/Camera Structure 1 M Aluminium 4.27 4.27 Front MountBlock 1 M Aluminium 0.17 0.17 Bottom Roller Mount Block 1 M Aluminium 0.04 0.044 RollingElements McGill Precision Roller 2 MCYR-17-S C McGILL Steel 0.15 0.306 BearingShaft 1 M Stainless Steel 0.26 0.255 Bearing (Pair) 1 2X7304BEGA M SKF Stainless Steel 0.28 0.28 ClampingRing_Roller 4 M 0.02 0.064 RBC Bearings - Under Roller 1 CS24LWX M RBC Bearings Steel 0.08 0.076 17.1129

PFIS – Mechanical Overview VERSION 1.0 10 March 2003 cdr... · Mechanical Overview Document...

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Transcript of PFIS – Mechanical Overview VERSION 1.0 10 March 2003 cdr... · Mechanical Overview Document...