ESI Collimator Actuator Alignment Procedure
Jim Burrous - Carol Harper
This document is an abreviated procedure for aligning the collimator actuators. For more detailed information consult the Galil and the Renishaw manuals. The purpose of this procedure is to align the fiducials and the primary and the secondary limits.
There are three collimator actuators that are mounted
on the lower section of the ESI space frame. Each actuator is held rigidly
in place by a metal cylinder attached to a bottom corner of the structure.
The moving portion, refered to as the car, has Renishaw encoder tape applied
to it as well as a magnetic fiducial which can be sensed by the Renishaw
readhead. The readhead is fixed to the actuator framework. Three opto-interruptors
are located on the opposite side of the Renishaw readhead. These serve
as forward and reverse limits and a rough home fiducial. The index is the
true home fiducial. The car has a blocking flag that rides with it and
interrupts the light path for the opto-interrupters. Limits and home logic
are both active low. When the flag is in the sensor the signal is low.
The primary limits are the opto-interrupters which feed a signal to the Galil controller and halt or inhibit further motion in that direction of travel. The secondary limits physically break the motor power and feedback a signal to the controller indicating that the secondary limit has been activated. Once the secondary limit has been activated you can no longer move the stage using Galil commands. At this point, first issue a MO command (motor off) to disable all axes, then disconnect the motor leads and apply power directly to the motor by using a battery or power supply. This procedure will allow you to back out of the secondary limit. If a forward limit has been reached the power source should be connected so that the negative lead on the motor is connected to the positive lead on the power supply, this will drive it in the negative direction and out of the limit. Use extreme caution during this portion of the procedure because all safety features have been overridden. A small amount of motion is expected due to hysteresis in the secondary limit switch to deactivate the power lock out. At this point the motor leads can be reattached in their original position and you can resume using Galil commands.
Refer to the definitions at the end of the document.
1. Power up the actuator, then set:
ST ( stop)
-the system may initialize on and be running a program
ERx=500 (error limit)
-set error magnitude to some number, 500 units of encoder error will halt motion
OE=1,1,1,1,1,1,1,1 (off on error)
-enables off on error for all axes A-H
2. Check the Renishaw for proper alignment:
A green light on the Renishaw indicates that it is properly aligned. Proceed to step 4 to check for a green light along the full length of travel.
If there is no green light then substitute an EL 1236 interupt box in place of the EL 1238. This will allow you to check the Renishaw readhead over its full range of travel before engaging the dual loop mode. You must check for a green light over the full length of travel. To do this issue a DV0 command that is appropriate for the axis. For example if E is the axis then:
DV,,,,0 (dual loop)
-0 disables the dual loop mode on the E axis
-to jog follow steps 4-6
-reinstall the EL 1238, you must now run under dual loop mode
If the light is not green over the full range of travel proceed to step 3.
3. Adjust the Renishaw for a green light. Refer to the Renishaw manual for the adjustment procedure. The RGH22Y readhead is the one being used, this allows for 0.1 micron resolution.
4. Set Galil parameters:
DV,,,,1 (dual loop)
-dual loop, 1 enables the dual loop mode on the E axis
-these settings allow fast motion for rough positioning
5. Turn on the optical fiducial and limits by setting:
CBn (clear bit)
-if the output port is E, then you would set CB9
-the optical fiducial will now look for limits
-this bit is active low
-there are 2 optical limits, 1 optical fiducial and 1 magnetic fiducial that works with the Renishaw
6. Jog to place the flag anywhere in the home optical fiducial:
-keep jogging until firmly on the flag, +n drives it away from the motor, -n toward the motor
-the jog speed is not important, use a value less than or equal to 10000
BGx (begin motion)
pre-type STx (stop motion)
then <CR> when you want to stop
7. Find the edge of the flag under the fiducial closest to the motor:
FEx (find edge)
BGx (begin motion)
8.Reset the motion parameters:
-256000 is the maximum setting, it will decelerate instantly
9. Find the magnetic fiducial index:
The edge of the optical home fiducial (found by FE) and the magnetic Renishaw index (found by FI) should be slightly offset.
FIx (find index)
BGx (begin motion)
After motion is complete:
MOx (motor off)
-this is our absolute reference point which we will call "home"
-the Galil will automatically zero the primary encoder value once the index has been found
10. Adjust the home optical fiducial to be very near the motor side of the flag but blocked. Check using:
MG_HMx (message command)
-if =1 then it's seeing the light, if =0 its blocked
-we want the number returned to be 0
11.Reset both encoders to zero:
For the dual loop configuration there are two encoders, a primary and a secondary. The Renishaw is wired in as the primary encoder and the motor encoder is the secondary encoder.
DPx=0 (define position)
-the primary encoder
DEx=0 (define position)
-the secondary encoder
12. Drive to pre-existing forward software limit and check the software limit against the data base:
JGx =10000 (jog)
-this will jog and stop at the limit
PAx =FLx (position absolute)
-this will go to the limit position
13.Move the forward fiducial to be slightly beyond the flag edge opposite the motor.
14. Adjust the forward secondary limit to be approximately 1/16" from activation. Adjustment of this is an iterative process of activating the switch and then removing the mounting plate to allow the switch to reset.
-secure the adjusting plate.
15. Turn the forward hardstop screw so that it is in contact with the slide. It is hidden below the forward secondary limit .
-next back off 3 turns until there is about 1/8th inch clearance
-secure the lock nut
16. Repeat steps 12-15 for the reverse limits.
x = axis used, output ports
1 = E
2 = F
3 = G
n = number
Galil command font
axis equilvalents = A-H