Instrument Control Software Blanco RC Spectrograph
|4.||RC Spectrograph description|
LabView based Motion Control
The update of the RC Spectrograph is based on the step motors and encoders subtitution by SilverMax (TM) intelligent motors, from QuickSilver Controls Inc.
The SilverMax (TM) is a fully integrated motion control system with a motion trajectory controller, a motor driver electronics, a position encoder and a motor, all contained in one unit.
SilverMax (TM) connects to a standard PC RS-485 interface.
The SilverMax (TM) motor brings a commands set that permit move motors, controlling different movement profiles: position, speed and time.
See main SilverMax (TM) motor characteristics in Apendix A.
The following mechanisms were updated:
|Slit 0 to 50.000 microns|
|Comparison Light Lens in - out|
|Inner Filter bolt Filters: 1 to 5|
|Outer Filter bolt Filters: 1 to 5|
|Collimator 220 - 760 Durant counter|
|Grating 85.6 degrees|
|Newall Mask South Mask, North Mask, Close, Open|
Once installed the RC Spectrograph in the telescope and before energizing the Power Supply & Interface Box, verify the following:
All motors should be connected to the Power Supply & Interface Box using the cables labeled for each motor.
Collimator and Grating have brakes wich should be in the lock position and their cable connected to the Power Supply & Interface Box Clamp connector.
The unit Power Supply & Interface Box uses some safety limit switch. To do this, other cables should be connected to it, their connectors are labeled. To avoid wrong operation or damage in the mechanisms, be specially careful with position cables.
Connect the RS - 485 cable to the Power Supply & Interface Box and to the casscage patch panel. The patch panel connector is labeled to be used in the RC - Spectrograph.
Untie all the cranks and assure them.
All switches in the Power Supply & Interface Box of all motors wished to be remote controled, should be ON.
Connect the 110Vac cable to the Power Supply & Interface Box.
Init the motors with the LabView control program.
Reference:REF8912 CH8912.900-A2 Block Diagram.
3.2 Control Panel
In the 4m RC Spectrograph LabView Control Panel (Figure 3.1) there are:
data entry displays,
control button to move the devices, and
Control button actives direct form movement, has the following colors code:
yellow: the device was activated
blue: the device this being monitoring
green: the device is in position
Controls and data entry
Slit: Clicking in the Slit Target display box and entering the new slit position value (arcsec).
The Slit mechanism will be moved to the new position by pressing the GO button.
The current slit width display (in microns) will be updated in real time.
Comparison Ligth Lens: Upon activating one of the OUT or IN button the device will be moved.
Upper Filter Bolt: Upon press one of these buttons, numbered of 1 to 5, the device will be moved to the chosen filter.
Lower Filter Bolt: Upon press one of these buttons, numbered of 1 to 5, the device will be moved to the chosen filter.
Collimator: Clicking in the Collimator Target display box and entering the new Collimator position value, the Collimator mechanism will be moved to the new position by pressing the GO button.
The current Collimator position display will be updated in real time.
Grating: Clicking in the Grating Target display box and entering the new Grating position value (wavelength), the Grating mechanism will be moved to the new position by pressing the GO button.
The current Grating position display (in degrees) will be updated in real time.
Newall Mask: Upon press one of these buttons, labeled as Closed,Mask North, Mask South and Open, the device will move the Newall Mask toward the chosen position.
Grating Setup: Is a Configuration Editor, can add or update the Grating data base and permits to move the grating to the extration position.
Init: The Init panel is an Initialization program for all motors and mechanisms, is necessary every time the motor will be power on cycle.
Once disconnectedt the motor of the source of power, loses the reference.
Motor Enable: Enable or disable motor and data entry panel control.
Stop: Stop motor.
Clear Status: Clean motor communication error status.
Exit: Leaves the program.
Safety limit switch status: Indicate if safety limit switches were activated.
Communication status: Indicate motor serial communication error.
Serial port activate: Shows serial port activity.
Wait, read RC Status: Is active when the program reads mechanisms status.
3.2 Grating Setup Panel
Gratings: Shows the grating data base.
Gratings Specs: Shows the grating characteristics
Current grating name: Indicates the current grating select
Save: Saves the grating name selected to work with
Edit Grating: To update the grating data base
Extract Grating: To move the grating mechanism and shows the extract grating panel.
Important:The grating motion control uses some of theparameters of the data base. For this is important to choose the correct grating and to check the parameters.
3.3 Extract grating panel
Extract position: Shows the grating extract position
Degraus: Shows the grating mechanism movement
Stop: Stops the grating motor
Safety limit switch status: Indicates if the limit safety switches were activated
3.4 Motor Enable panel
Enable or disable motor and data entry panel control (figure 3.4)
Enter: Updates the file with status motors
Exit: Leaves the program
3.5 Init panel
The Init panel control (figure 3.5) is an Initialization program for all motor and mechanisms, necessary every time the motor will be power on cycle.
The motor, once disconnected of the source of power, loses the reference.
If is attempted to move any mechanism, in these conditions, will be appear an error message indicating which motor must be initialized.
The initialization process consists in which the motor will move the mechanism to find the fiducial, when the motor finds it, update its internal counters and there can be moved to any valid position.
Init: Initialize each motor individualized with the name of the mechanism associated with motor:
Comparison Ligth Lens
Upper Filter Bolt
Inner Filter Bolt
Allows to consult the current status of all the motors, shown to the user through a colors code:
blue: motor enabled
yellow: motor disabled
red: communication error, the program could not be communicated with the motor.
coffee: not initialized
A waiting message will be displayed in the superior straight corner of the control panel
Exit: Leaves of the program.
3.6 Edit mechanism parameter
Permits to edit the parameter file, but these values are defined during the ingeniering setup. Is recommended not to modify them, since alter the operation of the RC Spectrograph.
A top view of the slit assembly is show in Figure 4.1.
Full slit length is 50 mm and range of slit width is from closure to 50 mm. Typical slit widths are from 140 to 200 microns (.140 to .200 mm) and the scale at the slit is approximately 6.7 arcsec/mm.
The drive micrometer is operated manually using the handwheel or by computer command to the SilverMax (TM) motor (address 1). For manual operation the micrometer scale is read through the viewing port, via two mirrors. One full turn of the micrometer handwheel produces .5 millimeter (500 microns) of linear motion. The numbers on the dial (0-50) represent hundredths of a millimeter (10 microns), and each minor division represents .002 millimeter (2 microns). Thus, maximum setting accuracy if 1 micron.
The SilverMax (TM) encoder have 4000 counts, is such that one turn of the micrometer corresponds to 10000 counts, so each encoder count is 0.125 microns. Since encoder accuracy is ± 1 count, accuracy of slit width as set by the computer, is also ± 1 microns. The Durant mechanical counter also provides 250 counts per micrometer revolution.
4.2 COMPARISON LIGHT LENS
When the comparison light lens is moved in, it completed the optical system designed to illuminate the slit as though the comparison light had come from the telescope entrance aperture. This lens is in only when the comparison light source (in the instrument rotator) is in use and the instrument rotator carriage (containing the remainder of the optical system) is in position 4. The location of the slide carrying the comparison light lens is shown in Figure 4.4. The drive mechanism for the slide is part of the slit, and comparison light lens drive assembly (Unit 7), as shown in the Figure 4.3. This drive is operated manually using the handwheel or remotely by computer commands to the SilverMax (TM) Motor (address 2). The readout dial provides local indication of IN or OUT position while internal limit switches provide this information to the SilverMax (TM) motor and LabView control. Figure 4.2 Slit and Comparison Light Lens Drive Assembly, external view (handwheel)
Ref: The complete optical diagram for the Comparison Light Source is shown in draw 2131.002-E10
4.3 Filter Bolt
Any one of the five filter bolt positions may be selected to provide the desired spectral range to the exposure meter. The filter bolt positioning drive screw may be driven locally by the handwheel or remotely by computer command to the SilverMax (TM) motor (address 2 for Upper Filter Bolt and 3 for Lower Filter Bolt).
The Durant mechanical counter is coupled directly to the motor shaft so the counter indications for the four filter positions are 0, 300, 600 and 900, respectively. The Filter Bolt may be removed as follows: on the left end of the housing, turn the latch one-half turn and open the housing end corner. With the handwheel engaged, turn it clockwise and drive the filter bolt assembly left as far as it will go. The filter bolt is retained in its holder by the bolt-detect-dovetail mechanism. Press down on the screw protruding from the left end of the filter bolt to remove it from its holder and the housing.
FILTER BOLT ASSEMBLY
The upper and lower filter bolts are contained in a housing that extends completely across the Spectrograph body as shown in Figure 4.5. The drive assembly (Unit 2) for both filter bolts is attached to the east end of the housing and the access door is on the west end, Figure 4.6. Note that the housing is cut away at the center to provide clearance for the Grating assembly. Also, each filter bolt has only four holes for mounting filters: the "Clear" position results from moving the filter bolt completely out of the beam.
Upper Filter Bolt
Filter number Durant Counter
Lower Filter bolt
Filter number Durant Counter
4.4 NEWALL FOCUS MASK
A single thin sheet of black anodized aluminum performs a function as a focus mask. The arrangement of the newall mask and its drive mechanism is shown in Figure 4.7. The mask may be operated manually using the pointer know or remotely by computer command to the SilverMax (TM) motor (address 7). Cam detents and a plunger ball permit precise positioning for manual operation. For remote operation, position indicating switches determine position, not the ball/detect arrangement. This is necessary since, if the ball spring is compressed enough to provide useable detect action, the motor is not able to drive the ball out of its detent. Figure 4.9 is a photograph of Newall Focus Mask Assembly (Unit 4). Figure 4.9a Newall Mask panel.
4.5 THE COLLIMATOR
The Collimator housing is mounted to the bottom of the Spectrograph casting at an angle of 11° as referenced to the instrument optical axis. The Collimator Focus Drive Assembly and the Collimator Focus Lock are attached to the housing as shown in Figure 4.10, below.
The collimator mirror is carried on a focusing mount inside the housing and is described below.
Collimator Optics. The Collimator mirror is an off-axis paraboloid, 225 mm in diameter, with a focal length of 1161mm (45.71"). Figure 4.11 shows the optical arrangement of the Collimator. The full parabolic mirror from which the parabolic section was cut is shown as a dotted outline. Note that the axis of this parabolic mirror forms an angle of 11° with the instrument axis. Also, the angle between the line connecting the center of the section with the center of the grating is 11°.
The f7.6 beam from the point source at the slit is collimated into a 152mm (6") diameter beam for the grating. Note that the focussing motion is parallel to the parabolic axis, so the beam moves laterally (north and south) in respect to the face of the parabolic section during focussing.
Collimator Focussing. Details of the Collimator focusing mechanism are shown in Figures 4.12 and 4.13. The cylindrical housing supports the "Collimator Change Subassembly", which is actually a mirror cell assembly. The cylindrical mirror housing is attached to a sliding plate that is held between a pair of dove-tail plates. The sliding plate is drive up and down over a range of 38.1 mm (1.5 inches) by the drive ball of the Focus Drive Assembly.
The collimator mirror cell is support in the housing by three block, which also contain collimator adjustment screws (Figure 4.13). Three "ears" inside the housing contain spring-loaded pins that hold the cell against the support blocks. The three support blocks must be removed to remove the Collimator Change Subassembly.
The Collimator Subassembly weights 25 pounds and must be properly supported during removal.
Focus Drive Assembly. The Collimator Focus Drive Assembly is bolted to the Collimator housing and couples to the mirror housing sliding base via the drive ball, as shown in Figures 4.12 and 4.13. Both the remotely operated drive motor M12 and the manual handwheel drive the worm shaft (Figure 4.13). This same shaft drives the Durant mechanical counter. The manual drive bevel gear may be disengaged by moving the MANUAL FOCUS ENGAGE-DISENGAGE slide up, pulling out on the handwheel, then moving the side back down (the slide is shown 90° out of position in Figure 4.13). The worm-driven gear drives the lead screw that drives the ball carriage up and down, as shown in Figure 4.12.
The drive SilverMax (TM) motor(M12) requires 4000 steps per revolution and drives the Durant mechanical counter thru a 2.5 to 1 reduction. The Durant Counter indicates 100 counts per revolution, with the last digit indicated by the index on the last dial. Therefore, since the motor and handwheel drive the same shaft, one revolution of the drive motor on the handwheel corresponds to 40 counts on the Durant Counter. Thus the resolution of the Durant counter is 100 motor steps per count (that is, per small division on last dial).
The worm on the drive shaft drives its geat at a 20:1 reduction, so one revolution of the gear shaft represents 4000x20 = 80000 motor steps.
The drive output shaft drives the lead screw thru an right angle 1:1 gear pair. The lead screw has a double lead of 2 mm pitch so moves its nut (the ball carriage) a total of 4 mm, per revolution. Since each revolution represents 80000 motor steps, the movement of the drive ball and the collimator mirror is 4/80000 = .00005 mm per motor step.
The total travel of the collimator mirror is 38.1 mm, requiring 9.525 trns of the lead screw, shich is 9.525 x 20= 190.5 motor revolutions and 190.5 x 4000 =
762,100 motor steps. The total number of counts on the Durant counter is 7620 and the total number indicated by the encoder is 762. In terms of resolution of the position of the collimator mirror, the Durant Counter is .005 mm per count.
Collimator focus Lock. To insure accurate resetting, the Collimator focus is always set by driving the collimator mirror up (skyward), then clamping it in position. The action of the Collimator focus Lock is shown in Figure 4.14. The Collimator mirror is normally clamped in position by pressure of the lock spring thru the transfer pin to the moveable dovetail section (Figure 4.13). The force transmitted to this dovetail section is sufficient to hold the sliding base in position. The collimator may be unlocked manually by throwing the locking lever to the UNLOCKED position, causing the lockin arm to rotate about its pivot pin and release pressure on the transfer pin. Remote unlocking is accomplished by energizing the unlocking solenoid. The solenoid over-rides the force of the locking spring, releasing the pressure on the transfer pin to unclamp the dovetail section. (Figure 4.15 Collimator Drive Assembly)
4.6 GRATING MOUNT AND DRIVE.
In order to fully utilize a diffraction grating, the angular position of the grating must be adjustable over a rather large range. To obtain a particular spectrum on the camera plate, the grating must be set at an angular position that is determined by three factors:
1. Wavelength (at center of plate).
2. Spectral order (usually n=1, or n=2).
3. Grating spacing (line/mm).
Mechanical details of the Grating Mount and Drive Assembly follow and photographs of the external components are below (Figure 4.16).
The arrangement of the grating mount and its drive assembly is shown in Figure 4.17. The mount may be rotated through an angle of 85.6 degrees to permit orientation of the grating as required to generate the desired spectra. The grating cell slides into the totating ount and may be inserted or removed through the "Grating Cell Access Door". The grating mount, the coupling shaft (Figure 4.21) and drive output gear form a rigid unit that was aligned and pinned at assembly. Also, the grating support weldment, the instrument housing and the drive housing form a rigid base for the rotating mechanism. All bearings in the rotating unit are preloaded to prevent any axial motion as the instrument is swung on its side.
The grating clamp system consists of two clamp and disc brake arrangements, one located at each end of the grating mount. The clamp actuating mechanism is very similar to the Collimator focus Lock mechanism and is shown in Figure 4.18 and 4.19. In this case, the clamping force from the actuating lever is transmitted to a second lever via a transfer pin, then through a second transfer pin to a force splitting cylinder. The clamping force from this cylinder is directed down the two output transfer pins, through a right angle sliding arrangement to the disk brake. Operation of the clamp generates no rotational or lateral movement and the clamping action is sufficiently strong to hold the grating mount in position under any operating conditions.
Grating Drive Assembly
Details of the Grating Drive Assembly are shown in Figure 4.20 and 4.21. As noted above, the output gear is ridigly connected to the grating mount, so any mechanical adjustments must be referenced to this fixed position. The large spring attached to the gear hub applies more rotational force to the shaft than the maximum force caused by mount unbalance, thus preventing backlash problems. The worm that drives this output gear provides a 360:1 step-down ratio. Since the grating drive motor (M14) is coupled directly to this shaft, one motor revolution represents on degree of output shaft rotation. Both the Durant mechanical counter and encoder are coupled to the worm shaft with a 1:1 ratio and have outputs of 100 counts per revolution. Note, however, that the "one-hundredth" count of the Durant counter is represented by index marks on the last dial, so for dial numbers, the Durant Counter actually reads only 10 counts per revolution. Thus for the maximum rotation of 85.6°, the Durant counter will indicate 856 counts.
Referring to Figure 4.20, note that adjustment of the worm for proper alignment with its gear is accomplished by adjusting the set screws in the drive housing to move the worm mounting plate as required. The manual drive handwheel couples to the worm shaft throught bevel gears with a 3:1 step down, so the manual handwheel requires .3 revolutions per degree of drive shaft rotation.
Since the motor requires 200 steps per revolution, the resolution of the encoder is 2 motor steps per count. The maximum motor rate is 625 pulses per sec, corresponding to a grating rotation of approximately 3 degrees per second.
Baud Rate: 19200
RS - 485
Comparison Light Lens 2
Inner Filter bolt 3
Outer Filter bolt 4
Newall Mask 7
Baud rate: 19200
The 4m RC-Spectrograph control GUI software leaves in ctioja:/home/rcspec/rc
The structure of the source directory tree is as follows:
control_panel.vi LabView executable control program
files data files
5. Setup Motor
motors.dat motors data file
grating.dat current grating name file
parameter.dat RC parameter file
181.txt gratings parameter files
181-2.txt " "
setfiles config executable programs