Review on collimator movement
with stepping motors
Mechanical design and
SPS results
O. Aberle
4th November 2005
Design work from many colleagues in TS/MME,
Stefano Redaelli for the SPS test results
Photos from P. Francon
05.11.05
Review on collimator movement with stepping
motors
Overview
 Mechanical design
 Motion of collimator jaws
 Auto retraction
 SPS tests
 Results from SPS tests
 Results on Prototype No. 3
 Conclusions
05.11.05
Review on collimator movement with stepping
motors
Mechanical design
UP
M1
LEFT
M2
DOWN
Beam
M3
RIGHT
M4
For each collimator: 4 motors + 4 Resolver + 4 jaw positions + 2 gaps
14 devices to move / control jaw positions and gap opening
Stepping motors
Precise in relative (5-10mm) but may loose steps
Resolvers
Count the steps of motor. Decoupled from mechanical
structure (cannot see mechanical plays!)
External measurements (potentiometers, LVDT’s, palmers): measure directly jaws
Our approach:
05.11.05
Adjust the motor settings. Use the (calibrated) external
measurement devices as a reference in the control room.
Review on collimator movement with stepping
motors
Mechanical design
Vacuum tank
Inside gap
Outside gap
Each collimator measured
open in metrology:
-Full gap
-Mech. stop/Jaw surface
Movement
Mechanical
end-stop
05.11.05
Review on collimator movement with stepping
motors
Motion of collimator jaw
CFC jaw
Torque meter
Vacuum tank
Cooling pipes
Glidcop bar
Transmission
Precision screw
05.11.05
Sliding
tables
Motor
Review on collimator movement with stepping
motors
Return spring
Motion of collimator jaw
05.11.05
Review on collimator movement with stepping
motors
Motion of collimator jaw
End stop
Return spring
Sliding table
Coupling
Motor axis
Screw support
05.11.05
Precision screw
Review on collimator movement with stepping
motors
Motor support
Auto retraction, Angle limitation
Motor
Return spring
05.11.05
Rigid bar
Rack and Pinion
Pin hole/slot (3mm)
Review on collimator movement with stepping
motors
Auto retraction, Angle limitation
Auto retraction
• One system: 2 sets of springs (dia. 5 and 6.3 mm) available
• for 3 types of collimators (CFC, CU and W jaw material)
• for 4 different orientations (0, 90, 45 and 135 °)
• Works in case of power cut (condition: Mechanics Ok)
• Tested vertically with 15 kg loaded (Tungsten case)
• Limitations: To start movement, minimum spring pre-load needed
• Back up: One motor can drive the jaw out against the angle limitation system
Angle limitation
•
Given by the mechanical play (3 mm on 1 m jaw length)
• Blocks the angle (with powered motor)
05.11.05
Review on collimator movement with stepping
motors
SPS tests
Resolver
Motor
Transmission
to jaw
Side view
Potentiometer
View from bottom
Different sensor installation
for SPS and TT40
prototypes…
05.11.05
LVDT
Review on collimator movement with stepping
motors
Results from SPS tests
Calibration of single motor
(test bench)
motor and resolver
 Verify step/resolver calibration
 Calibration of jaw displacement versus
motor setting / resolver readings
 Measure mechanical plays
 Measure minimum jaw step
Calibration with open
collimator
Calibration at the metrology
(with close collimator)
05.11.05
 Verify correct functioning of
 Provide the absolute reference with
respect to the beam trajectory
with final sensor configuration
Review on collimator movement with stepping
motors
Measurements at the metrology
Absolute error with this setup  3 mm
05.11.05
Review on collimator movement with stepping
motors
Results from SPS tests
 Potentiometers: Resolution  40-50 mm (some sensor better,  20 mm)
 Resolvers: absolute error  80 mm (expected 5 mm).
For motor control (lost steps?)
 LVDT’s: Resolution  15 mm in laboratory tests.
(re-calibrations regularly needed - feasible for > 500 sensors in radiation environment?)
 Capacitive sensor: Resolution  1 mm; not radiation resistant
 Mechanical play:
40 mm for SPS prototype
 10 mm for TT40 prototype
 Minimum step for jaws = 5 mm
05.11.05
Review on collimator movement with stepping
motors
Preliminary results from Prototype 3
Static torque measurement on Motor 1
Vertical, CFC jaw, upper jaw downwards
0.35
0.3
Torque (Nm)
0.25
0.2
0.15
0.1
“Soft” point?
0.05
0
0
5
10
15
20
25
Position [mm] (after switch out)
05.11.05
Review on collimator movement with stepping
motors
30
35
Preliminary results from Prototype 3
First 1.3 mm of the collimator movement in
steps of 50 microns
14
Motor 1
Deviation from target
position [mum]
12
Motor 2
10
8
Deviation from
target over full
range: 50 mm
6
4
2
10
00
11
00
12
00
90
0
80
0
70
0
60
0
50
0
40
0
30
0
20
0
Po
sit
i
on
-2
10
0
0
-4
-6
Position [mum]
05.11.05
Review on collimator movement with stepping
motors
Palmer (±3 mm),
hand aligned
No vacuum,
open collimator,
No RF contacts
Conclusions
o
Reproducibility of the jaw position:
<10 mm
o
Mechanical play:
 20 mm
o
Absolute position knowledge in laboratory:
(full mechanical chain)
 100 mm = 0.5 s
(LHC, top energy)
o
Alignment in tunnel:
0.1 to 0.2 mm
Each axis might need a calibration curve
Open points:
Test the different orientations
Life time/ cycling
Effect vacuum
Determine safety margin for each type and orientation
Risks: Alignment screw/motor, wear and aging, limitation in auto-retraction,
Safety factor of 2 desirable
05.11.05
Review on collimator movement with stepping
motors