Chapter 9 - Mirror 2 (Secondary Mirror)
The adjusting device for the secondary mirror serves to re-adjust
the M2 mirror according to optical requirements during operation
of the telescope. For this purpose, the Z re-adjustment of the
axis direction of the mirrors is used for active closed loop focus
control via the Shack on-line image analyser of the telescope.
X-Y re-adjustment (normal to the mirror axis) serves as closed
loop centering correction of the mirror system.
For the Z movement, two linear guiders are provided in the adjusting
device. The X-Y movement is carried out via a pantographic mechanism
with conically arranged guide spindles. Thus the X-Y movement
is not in a straight line, but is around the centre of curvature
of the M2 mirror, thus achieving coma correction without change
in pointing.
X-Y Motion
- Range: +/- 4mm
Positioning Accuracy (over whole range): 10 micrometre
Maximum Speed: 1mm/ sec
Z Motion
- Range: +/- 20mm
Positioning Accuracy (over whole range): 5 micrometre
Lateral Shift (over whole range): 50 micrometre
Maximum Speed: 2mm/ sec
The maximum lateral deflection of the plate support with the outer
ring between horizontal and vertical position of the whole unit:
15 micrometre.
The X-Y and Z re-adjustment are carried out in the M2 VME system.
As the three axes are not used at the same time, they are mounted
in a multiplex mode, thus saving space and heat dissipation in
the optical field.
The motion and positioning of the X and Y axes are obtained by
the rotation of spindles. These motions are effected by a torque
motor controlled in torque, velocity and position in a proportional
integral-type servo loop system.
An incremental encoder delivers the actual position. The final
positions are reached by reading out the position values from
the incremental encoder counter card.
The zero pulse of the incremental counter is used during initialisation
as an absolute position on the axes.
Final positioning is effected by means of an electro-magnetic
clutch.
Limit positions of the range are provided by inductive proximity
sensors. For security reasons, mechanical end-switches are available
as final limit positions.
The focusing motion is performed by the rotation of a torque motor
through a spindle. The Z re-adjustment is controlled in torque,
velocity and position by a proportional integral loop. An absolute
encoder provides the actual position directly to the VME system.
Final positioning is effected by means of an electro-magnetic
clutch. Inductive proximity sensors are used to fix the range
of motion, and mechanical end-switches are available in order
to disable the power amplifier.
- Inland Torque Motor QT6301 576W; Kt=1,6 lb ft/ A (Qty
3).
Inland Tachometer TG2179B; maximum voltage sensitivity 0.75V
per rad/s (qty 3).
Inland Power Servo Amplifier DCM 70/14 1kW ZF Type 2LNS330-OQKO.
Siemans Clutch EBD3V24V (qty 3).
Heidenhain Incremental Encoder Minirod 450; 1000 lines/ rev
(qty 2).
Heidenhain Evaluation and Interpolation Electronic EXE 602B;
interpolation factor 25 (qty 2).
Elestra Absolute Encoder AE65M; 1024 lines/ 64 revolutions.
- M2PAON70VO* - "Negated"
M2MTXSELO* - "Negated"
M2MTYSELO* - "Negated"
M2MTZSELO* - "Negated"
M2IERESETXO* - "Negated"
M2IERESETYO* - "Negated"
M2IEBREADO* - "Negated"
M2IECSSELXO* - "Negated"
M2IECSSELYO* - "Negated"
M2AELATCHO
M2AEUP_DOWN
M2ILENABLEO* - "Negated"
M2ILOVERRO* - "Negated"
M2OFF5VO* - "Negated"
- Set outputs to default settings.
Read safety/ protection inputs:
| INPUTS | NORMAL STATUS | IF NOT, CHECK ...
|
| PAFAULTI* | Negated | Inland power amplifier
|
| IEERRIX* | Negated | Heidenhain EXE 602 "X"
|
| IEERRYI* | Negated | Heidenhain EXE602 "Y"
|
| LSXLOWI* | Asserted | Move X in opposite direction
|
| LSXHIGHI* | Asserted | Move X in opposite direction
|
| LSYLOWI* | Asserted | Move Y in opposite direction
|
| LSYHIGHI* | Asserted | Move Y in opposite direction
|
| LSZLOWI* | Asserted | Move Z in opposite direction
|
| LSZHIGHI* | Asserted | Move Z in opposite direction
|
| ILEMSTOI | Negated | Emergency Stop Pushbutton EMSTO has not been released
|
| TEMP40I* | Negated | Temperature in M2 electronic unit higher than 40 degrees C
|
Select a drive system (M2MTXSELO*, M2MTYSELO* or M2MTZSELO*).
Note: only one system may be asserted.
Apply power to the Inland power amplifier (M2PAON70V0O*).
Delay before next operation of 100ms.
Enable the power amplifier (M2ILENABLE*); the amplifier will
energise if no end-stop condition exists. If the drive system
is at the end-stop:
- Read the limit positions.
Disable the interlock (M2ILOVERRO*).
Move in the opposite direction.
Reset M2ILOVERRO* to the default setting.
The required positioning is obtained by applying a velocity
reference and reading the incremental encoder counter card, or
the absolute encoder of the Z drive.
During positioning, check:
- M2PACUR analog input voltage is proportional to Inland
motor current (conversion factor: 0,66V per Ampere).
The status of the safety/ protection inputs.
At these positions:
- De-select the drive system. Delay before next operation:
100ms.
Re-check the poaition. If the correct position is obtained,
disable the power amplifier (M2PAENABLE*); delay 200ms, switch
off the power to the amplifier (M2PAON70V*). If not, re-select
the drive system, wait 100ms and position again.
9.3.3
Reading Out The Incremental Encoder
The X-Y encoder system has a resolution of 4000 lines per revolution.
With a value of 1mm linear spindle displacement per revolution,
the theoretical resolution is 0.25 micrometre. The specification
of 10 micrometre allows a tolerance of +/- 40 counting pulses.
Initialisation
After the command M2IERESETX* or M2IERESETY*, the X or Y spindle
drive system moves until it finds an absolute position that is
defined by the detected zero pulse ZP from the encoder.
The flag M2IEZEROX* or M2IEZEROY* indicates that the zero pulse
position has been registered and must be the first read out. The
relative position from the zero pulse can be read at any moment
through the command M2IECSSELX* or M2IECSSELY*.
The activation of these commands registers the current counter
data and must stay active until the end of the read out sequence;
transfer of 4*8 bit counter values. M2IEDREADY*, common to X and
Y drive systems, indicates that the 8 bit counter values are available.
The command M2IEBREAD* sent from local VME acknowledges to the
encoder counter that it can make the next byte and the handshake
M2IEDREADY* available. At the read out of the last byte, the command
M2IECSSELX* or M2IECSSELY* is de-activated.
Post Initialisation
After initialisation, the X or Y drive system displacement is
controlled by reading out the actual position through the incremental
encoder counter card.
The range initialisation is set through the movement of the drive
system, from one limit position to the other, and the calculation
of the middle position.
The Z absolute encoder system has a resolution of 1024 lines per
revolution. The theoretical resolution for the spindle displacement
is close to 1 micrometre. The specified range of +/- 20mm with
a spindle displacement of 1mm per revolution forces the selection
of the 64 turn absolute encoder.
The range initialisation is set through the absolute positions
at the two limits (in binary code) and the calculation of the
middle position.
The command M2OFF5V* allows the disabling of the 5V power supply
to the encoders X, Y and Z, and all the inductive proximity sensors
in the M2 unit when the X, Y and Z directions do not need to be
adjusted during a whole night of observation.
The signals in the Mirror 2 subsystem are divided into the following
groups that indicate where the signals originate (inputs to the
computer) or where they have to be routed (outputs from the computer):
- PA: Power amplifier signals
MT: Motor signals
AE: Absolute encoder signals
IE: Incremental encoder signals
LS: Limit switch signals
IL: Interlock signals
xx: Miscellaneous signals (where "xx" is not any
of the previous)
The above abbreviations are used as the second prefix after the
standard prefix M2 for all Mirror 2 signals.
| NAME | TYPE | DESCRIPTION |
| PACURI | AI*12 | PA current to motor X, Y or Z (1 common PA)
|
| PAVREFO | AO*12 | Velocity reference to X, Y or Z
|
| PAFAULTI* | DI*1 | PA fault indicator |
| PAON70VO* | DO*1 | Switch ON 70V busbar voltage to amplifier
|
| NAME | TYPE | DESCRIPTION |
| MTXSELO* | DO*1 | Select X drive system (motor, tacho, brake)
|
| MTYSELO* | DO*1 | Select Y drive system (motor, tacho, brake)
|
| MTZSELO* | DO*1 | Select Z drive system (motor, tacho, brake)
|
| NAME | TYPE | DESCRIPTION |
| IEDCH-DI | DI*8 | Data channel (common for X and Y positions)
|
| IEZEROXI* | DI*1 | Zero pulse detected for system X
|
| IEZEROYI* | DI*1 | Zero pulse detected for system Y
|
| IEDREADYI* | DI*1 | Data ready handshake signal (common for X and Y)
|
| IERESETXO* | DO*1 | Reset incremental encoder counter X
|
| IERESETYO* | DO*1 | Reset incremental encoder counter Y
|
| IEBREADO* | DO*1 | Byte read handshake signal (common to X and Y)
|
| IECSELXO* | DO*1 | Channel select X |
| IECSELYO* | DO*1 | Channel select Y |
| IEERRXI* | DI*1 | Channel X pulse shaping electronics error
|
| IEERRYI* | DI*1 | Channel Y pulse shaping electronics error
|
| NAME | TYPE | DESCRIPTION |
| AEDCH-DI | DI*8 | Data channel |
| AEDCH-DI | DI*8 | Data channel |
| AELATCHO | DO*1 | Latch data channel value
|
| AEUP/DOWNO | DO*1 | Up counting rotation direction
|
| NAME | TYPE | DESCRIPTION |
| LSXLOWI* | DI*1 | Low limit detected, system X
|
| LSYLOWI* | DI*1 | Low limit detected, system Y
|
| LSZLOWI* | DI*1 | Low limit detected, system Z
|
| LSXHIGHI* | DI*1 | High limit detected, system X
|
| LSYHIGHI* | DI*1 | High limit detected, system Y
|
| LSZHIGHI* | DI*1 | High limit detected, system Z
|
| NAME | TYPE | DESCRIPTION |
| ILENABLEO* | DO*1 | Enable amplifier and disengage selected brake
|
| ILOVERRO* | DO*1 | Override interlock |
| ILEMSTOI | DI*1 | Emergency stop pushbutton
|
| NAME | TYPE | DESCRIPTION |
| TEMP40I* | DI*1 | M2 cabinet, overtemperature 40 deg. C
|
| OFF5VO* | DO*1 | Incremental encoder + limit switch power off (5V)
|
| SIGNAL | BOARD | BIT | BIT SIZE |
TERMINAL STRIP | ACRO PIN | ACTIVE LEVEL |
DESCRIPTION |
| AEDCH-D08I | /acro0 | 0 | 1 | MTS1-15
| B32 | HIGH | absolute encoder high byte lsb
|
| AEDCH-D09I | /acro0 | 1 | 1 | MTS1-13
| B31 | HIGH | absolute encoder high byte |
| AEDCH-D10I | /acro0 | 2 | 1 | MTS1-11
| B30 | HIGH | absolute encoder high byte |
| AEDCH-D11I | /acro0 | 3 | 1 | MTS1-9
| B29 | HIGH | absolute encoder high byte |
| AEDCH-D12I | /acro0 | 4 | 1 | MTS1-7
| B28 | HIGH | absolute encoder high byte |
| AEDCH-D13I | /acro0 | 5 | 1 | MTS1-5
| B27 | HIGH | absolute encoder high byte |
| AEDCH-D14I | /acro0 | 6 | 1 | MTS1-3
| B26 | HIGH | absolute encoder high byte |
| AEDCH-D15I | /acro0 | 7 | 1 | MTS1-1
| B25 | HIGH | absolute encoder high byte msb
|
| | | | | |
| |
| | | | | |
| |
| AEDCH-D00I | /acro0 | 8 | 1 | MTS1-31
| B24 | HIGH | absolute encoder low byte lsb
|
| AEDCH-D01I | /acro0 | 9 | 1 | MTS1-29
| B23 | HIGH | absolute encoder low byte |
| AEDCH-D02I | /acro0 | 10 | 1 | MTS1-27
| B22 | HIGH | absolute encoder low byte |
| AEDCH-D03I | /acro0 | 11 | 1 | MTS1-25
| B21 | HIGH | absolute encoder low byte |
| AEDCH-D04I | /acro0 | 12 | 1 | MTS1-23
| B20 | HIGH | absolute encoder low byte |
| AEDCH-D05I | /acro0 | 13 | 1 | MTS1-21
| B19 | HIGH | absolute encoder low byte |
| AEDCH-D06I | /acro0 | 14 | 1 | MTS1-19
| B18 | HIGH | absolute encoder low byte |
| AEDCH-D07I | /acro0 | 15 | 1 | MTS1-17
| B17 | HIGH | absolute encoder low byte msb
|
| | | | | |
| |
| | | | | |
| |
| PAON70VO | /acro0 | 16 | 1 | MTS1-47
| A32 | LOW | power on 70V busbar voltage to PA
|
| MTXSELO | /acro0 | 17 | 1 | MTS1-45
| A31 | LOW | select X drive system |
| MTYSELO | /acro0 | 18 | 1 | MTS1-43
| A30 | LOW | select Y drive system |
| MTZSELO | /acro0 | 19 | 1 | MTS1-41
| A29 | LOW | select Z drive system |
| OFF5VO | /acro0 | 20 | 1 | MTS1-39
| A28 | LOW | incr enc + lim switch power off
|
| AEUPDOWNO | /acro0 | 21 | 1 | MTS1-37
| A27 | HIGH | up counting rotation direction
|
| spare | | | | | |
| |
| AELATCHO | /acro0 | 23 | 1 | MTS1-33
| A25 | HIGH | latch data channel value |
