MODS Shutter Data Sheet General Description The MODS Shutters are integrated into the spectrograph cameras immediately behind the corrector where they mount to the inside surface of the corrector cell. The shutters use a pair of rotating blades to obstruct the light entering the camera. The shutter blades are driven from a common motor but with different gear ratios so each blade has a different range of travel. The BLUE and RED shutters are very similar but are mirror images regarding drive placement and have different gear ratios. Also, the sign of the motor moves is opposite between BLUE and RED; BLUE negative move = Closes Shutter RED positive move = Closes Shutter This affects the Limit Switch definitions and the signs of the move commands in the software. The blades are held in the open or closed positions with the motor power off using a spring loaded roller detent. Each shutter blade has two micro-switches that are used for OPEN and CLOSED indication. The OPEN and CLOSED limits are then derived using diode logic to OR the OPEN and CLOSED switches for each blade. Because the shutters open from the center outward along the slit, the edge of the field receives less light than the center. However, the shutter is quite close to the pupil so this effect is very small. For a 1.0 second exposure time the top and bottom of the slit receive 0.4% less light than the center. The percentage shading gets smaller for longer exposures. There is no shading at all in the dispersion direction. Rendering of Red Shutter Asm. Blade #1 (nearest to motor pinion) Blade #2 Shutter Roller Detent Shutter Motor Drive Gears Shutter Motor Blade Position Indicators Switches & Cams Inboard Switch = Blade OPEN Outboard Switch = Blade CLOSED
Drive Motor Motor Type Size 23 Step motor, 200 full steps per revolution, double-ended shaft Part # Superior # KML061F05 - D Rated Current: 2.7 amps/phase parallel (RMS) Rated Holding Torque: 170 in*oz Motor Connection Diagram A+ Red/White A- Red B+ Black/White B- Black Motor Controller Specifications Manufacturer & Model: IMS MicroLYNX 7 (#MX-CS100-701) Rated Current: 5amps RMS/phase, 7 amps peak/phase Rated Voltage: 24 to 75 VDC Rated Voltage: 24 to 75 VDC Daughterboards: Isolated Digital I/O (6 points) Motor Controller Settings MSEL = 10 10usteps/fullstep = 2000 microsteps/rev MUNIT = 2000 sets units to (2000 usteps/rev) gives velocity and accelerations in rev/sec MAC = 65 Acceleration Current = 65% = 4.5 amps peak MRC = 54 Run Current = 2.7 amps RMS *1.4 = 3.8 amps peak (3.8/7 = 54% ) MHC = 0 Motor Hold Current is zero ACLT=1 linear acceleration (default) ACCL=DECL = 20 acceleration rate (rev/sec^2) LDECL = 500 limit deceleration rate (rev/sec^2) Overtravel at Limit = (2*Pi* Blade Radius) * (Gear Reduction)* VM 2 /(2*LDECL) = 4.9mm (Blade Radius = 170mm, Gear Reduction = 16/87, VM=5 rev/sec, LDECL=500 rev/sec^2) Beware overtrave, must not decelerate shutter blades hard into limits Maximum Permitted Overtravel at Blade tips ~ 5mm VM= 5 VM= 0.5 max running speed (rev/sec) Homing speed to assert limit (rev/sec) Motor Controller I/O Connections Vpull: Must set DIP switches to use internal Pull-up to 6 VDC (not the default) GND: Microswitch Gnd I/O 21: Shutter Closed LIMIT sensor (two blade inputs OR d with blocking diodes) Active Low I/O 22: Shutter Open LIMIT sensor (two blade inputs OR d with blocking diodes), Active Low Must set DIP switches for I/O 21 and 22 to use internal Pull-up to 6 VDC (not the default) Blocking Diodes Required for Multiple Input connections from switches to LIMIT inputs, See Schematic
Extended I/O on Daughterboard Vpull: Must set DIP switches to use internal Pull-up to 6 VDC (not the default) GND: Microswitch Gnd I/O 31: Blade 1 CLOSED (also to CLOSED Limit) I/O 32: Blade 2 CLOSED (also to CLOSED Limit) I/O 33: Blade 1 OPEN (also to OPEN Limit) I/O 34: Blade 2 OPEN (also to OPEN Limit) I/O 35: Shutter + INPUT Input Sensors 11SM2-T micro-switches with roller end and flex leaf, wired to Normally Closed (NC) terminals Output Devices None Drive Mechanics Single Stepper motor drive with gear reduction and 1:1 HTD timing belt final drive to graphite/epoxy foam core blades Counter-rotation achieved with fixed ratio gearing which provides different travel for each blade. The different gear ratios are required due to the tilted corrector cells which are different for the red and blue cameras Blue Shutter motor/blade ratios are 16/84 for the bottom blade, Travel = 86 degrees 16/78 for the top blade, Travel = 93 degrees Blue Motor Steps = 200steps/rev * (84/16) * (86/360) = 251 full steps Red Shutter motor/blade ratios are 16/90 for the bottom blade, Travel = 79 degrees 16/72 for the top blade, Travel = 99 degrees Red Motor Steps = 200steps/rev * (90/16) * (79/360) = 247 full steps Hard overtravel limiting end stops to protect blades in open and closed positions Roller detent at end positions to maintain blade position with motor power off Limit switches on both blades for open and closed positions, CW AND CCW Limits Knob for manual override Performance With a Shutter Opening time of ~0.5 seconds and Closing time of ~0.5 seconds, an effective exposure time or 0.45 seconds is realized. This requires motor average velocity of ~ 500 fullsteps/sec and peak speed of ~1000 fullsteps/sec (VM=5) for a triangular velocity profile. A table (or computational algorithm) will be required to list VM and ACCL, DECL for a range of desired effective exposure times. Shutter Motion Control There are two roller micro-switches switches and cams on each blade to provide OPEN and CLOSED position feedback information and limit switch inputs. The cams have notches in their outer surface to actuate the switches. Switches are always asserted between cam notches, this prevents flapping of switch roller blades. Normal Operation Position Feedback requirements Narrow angle indication of SHUTTER OPEN on each blade Narrow angle indication of SHUTTER CLOSED on each blade
Inputs from Blade#1 and Blade#2 are logically OR d and sent to LIMIT inputs Switch, Cam, and Drive Controller Setup Each blade will have two cams with a narrow notch to de-assert the switch. One cam will have its notch centered with the blade closed the other cam will have its notch centered with the blade open. The switches will be adjusted so that the cam notch is centered on the switch roller in the final detented position. The switch bracket is adjusted on its slots to provide balanced over-travel and under-travel of the switches. It is important to verify that the switches are not de-asserted before the detent roller cam is in its notch. The switches will be wired to the NORMALLY CLOSED terminal. The switches will be in the NORMAL position (OPEN) when the shutter blades are at their limits of travel. This will pull down the drive inputs to ground when the switch roller is in the notch. This switch configuration assures detection of all normal states for both blades independently, prevents over-travel with Limits, and provides a wealth of diagnostic information in response to shutter mechanical and electrical failures. Fault Conditions and Detection Method 1. Either drive gear slips on ¼ gear shaft, producing incorrect phase angle between blades. Blade tips could collide at closure if not detected. Detected by OPEN or CLOSED bits not asserting (detection angle must be quite narrow) 2. A blade drive belt breaks, producing one blade moving and one blade flapping free. Blade tips could collide near closure if not detected. Detected by OPEN or CLOSED bits not asserting or a limit asserting at the wrong time. 3. OPEN or CLOSED indicator cam slips on blade shaft If a single OPEN or CLOSED cam slips, the corresponding cam on the other blade will still provide a LIMIT indication and prevent over-travel 4. Motor stalls, electrically fails, or pinion gear slips The Expected OPEN or CLOSED position will not be reached in commanded number of steps, a fault will be reported 5. Shutter is placed in an invalid position and then a move is executed Verify with status inquiry that shutter is in a valid OPEN or CLOSED position before initiating a move. 6. A microswitch fails OPEN Invalid state is indicated, alerting software. 7. Double Switch Bracket is mis-adjusted so that switches remain in Asserted position even when centered on cam notches. Both switches will indicated OPEN or CLOSED, an invalid state
Software Issues We have prior knowledge of the motor direction and the number of motor steps required to move from OPEN to CLOSED positions for both the BLUE and RED shutters. This information will be used to compute a trapezoidal velocity vs. time profile which will be executed precisely the same way for every opening or closing of a shutter. Main program just polls for request for action and stable states. 2 stable states both CLOSED want CLOSED Both OPEN want OPEN 2 states request action both CLOSED want OPEN Both OPEN want CLOSED Consolidate the Blade State evaluation into a single section of the program Include Limit State in evaluation section Generate specific Status message, actions and error messages for every Blade state Delete redundant subroutine for Blade State evaluation SHUTTER Questions How are errors reported to Operator? PRINT statements? What is error recovery process? Controlled in Microlynxx code? Why is REMOTE a background task? How does Count work? Why 2 Startup Startit ESC from HOST can halt Microlynxx program execution Can the HOST execute a status inquiry to the Microlynxx whit a Main program running? Can the HOST execute a status inquiry to the Microlynxx whit a Background program running? Notes: RSTATE variable sets local or remote mode. Set to remote in PLC code. HOST controls it?? Deleted TRIGGER as a variable. IO 30 includes it in State evaluation Deleted BETW variable Deleted separate SHUTTER procedure, use BLADSTAT for all status inquires from HOST BLADSTAT never returns to main program without usere intervention No background routines are used RSTATE variable sets local or remote mode
MODS Shutter State Table IO 35 is Shutter State Command from HE Box IO 35 is configured as High TRUE input Open switch gives High level (TRUE) due to internal Pull Closed up switch give Low level (FALSE) due to Pull down IO 35 = 1 CALLS the CLOSE subroutine IO 35 = 0 CALLS the OPEN subroutine IO 21 TRIGGER CCW Limit Digital Value Blade1 Blade2 Blade1 Blade2 TRUE reque CLOSE CLOSED Limit HE COMMAND State Description of Shutter State Binary SUM CLOSED CLOSED OPEN OPEN FALSE reque OPEN IO31 OR IO32 IO 30 IO 31 IO 32 IO 33 IO 34 IO 35 IO 21 1 2 4 8 16 COMMAND from HE Box Shutter Status Message Blade 1 Blade2 COMMAND is OPEN moving toward OPEN?? AJAR AJAR 0 0 0 0 0 0 0 COMMAND is OPEN CLOSED AJAR 1 1 0 0 0 0 1 COMMAND is OPEN AJAR COSED 2 0 1 0 0 0 1 COMMAND is OPEN Status prior to OPENING CLOSED CLOSED 3 1 1 0 0 0 1 COMMAND is OPEN OPEN AJAR 4 0 0 1 0 0 0 COMMAND is OPEN Both Limits Asserted OP & CL AJAR 5 1 0 1 0 0 1 COMMAND is OPEN Both Limits Asserted OPEN CLOSED 6 0 1 1 0 0 1 COMMAND is OPEN Both Limits Asserted OP & CL CLOSED 7 1 1 1 0 0 1 COMMAND is OPEN AJAR OPEN 8 0 0 0 1 0 0 COMMAND is OPEN Both Limits Asserted CLOSED OPEN 9 1 0 0 1 0 1 COMMAND is OPEN Both Limits Asserted AJAR OP & CL 10 0 1 0 1 0 1 COMMAND is OPEN Both Limits Asserted CLOSED OP & CL 11 1 1 0 1 0 1 COMMAND is OPEN stable OPEN state OPEN OPEN 12 0 0 1 1 0 0 COMMAND is OPEN Both Limits Asserted OP & CL OPEN 13 1 0 1 1 0 1 COMMAND is OPEN Both Limits Asserted OPEN OP & CL 14 0 1 1 1 0 1 COMMAND is OPEN Both Limits Asserted OP & CL OP & CL 15 1 1 1 1 0 1 COMMAND is CLOSED moving toward CLOSED?? AJAR AJAR 16 0 0 0 0 1 0 COMMAND is CLOSED CLOSED AJAR 17 1 0 0 0 1 1 COMMAND is CLOSED AJAR CLOSED 18 0 1 0 0 1 1 COMMAND is CLOSED stable CLOSED state CLOSED CLOSED 19 1 1 0 0 1 1 COMMAND is CLOSED OPEN AJAR 20 0 0 1 0 1 0 COMMAND is CLOSED Both Limits Asserted OP & CL AJAR 21 1 0 1 0 1 1 COMMAND is CLOSED Both Limits Asserted OPEN CLOSED 22 0 1 1 0 1 1 COMMAND is CLOSED Both Limits Asserted OP & CL CLOSED 23 1 1 1 0 1 1 COMMAND is CLOSED AJAR OPEN 24 0 0 0 1 1 0 COMMAND is CLOSED Both Limits Asserted CLOSED OPEN 25 1 0 0 1 1 1 COMMAND is CLOSED Both Limits Asserted AJAR OP & CL 26 0 1 0 1 1 1 COMMAND is CLOSED Both Limits Asserted CLOSED OP & CL 27 1 1 0 1 1 1 COMMAND is CLOSED Status prior to CLOSING OPEN OPEN 28 0 0 1 1 1 0 COMMAND is CLOSED Both Limits Asserted OP & CL OPEN 29 1 0 1 1 1 1 COMMAND is CLOSED Both Limits Asserted OPEN OP & CL 30 0 1 1 1 1 1 COMMAND is CLOSED Both Limits Asserted OP & CL OP & CL 31 1 1 1 1 1 1
Wiring Schematic