Undulator Motion Controls

1
Undulator Motion Controls

• Jim Welch
• June 9, 2009

J. WELCH welch_at_slac.stanford.edu
June 9, 2009 FAC, June 2009
2
Outline

• Basics
• Performance
• calibration
• motion
• Stability

3
Degrees of Freedom
-5 to 80 mm
Undulator
Q
BFW
BPM
/- 1 mm

• Girder x,y, (2X) and roll, control Q, BPM, BFW
  and undulator transverse positions.
• Undulator girder motion plus 85 mm of horizontal
  translation
• 33x6 total degrees of freedom for mechanical
  motion

4
Linear Potentiometers

• Six linear potentiometers provide indepenent
  on-line measurement of girder motion with about 5
  micron resolution.
• Also used for calibration of cam angles and
  motion verification.

5
Kinematics

• Girder is treated as a rigid body.
• Unique, invertable geometrical relations between
  the cams and the objects.
• Roller bearings on cams determine Q or BPM, and
  BFW transverse positions independently.

6
Matlab Motion Control Programs

• CVSd matlab routines for undulator motion
  control applications
• epics controls are also used

girderAngle2Axis girderCamSet
girderAxis2Angle girderCamWaitgirderAxisF
ind girderAxisFromCamAngles girderGeo
girderAxisMeasure girderLinearPot
girderAxisMove girderLinearPotZero
girderAxisSet girderLPOT2Axis
girderBFWMove girderMotorStatusReadgir
derBFWposition girderPositionPlotGui
girder_bump girderPositionPlotGui
girderCalReset girderQuadMovegirderCamA
ngleCalibrate girderQUADposition
girderRangeCheckgirderCamMotorRead
girderRotaryPot girderCamPot
girderScoreField_Integral_GUi Field_Integral_GUI
undulatorPositionPlotGuiundulatorPositionPlotGui
moveUndulatorQuadrupole_guimoveUndulatorQuadrupole
_gui scan_backlash segmentTranslatesegmentTranslat
eWait segmentTranslationStatus steer_undulator_gui
taper_control und_quad_align UndKact
UndKactMonitor UndulatorTaperControl
7
Motion Checking

• Accuracy check based on linear potentiometers
  which are good to about /- 5 microns.
• During initial system checkout, we found gross
  distortion in the motion due to software
  irregularities. (fixed)

8
Calibration

• Linear potentiometer reading versus cam angle.
  Should be sinusoidal.
• Phase is determined by matlab software. Period is
  determined by ANL software.

9
Calibration of Many

• Calibrate up to 33 cams at once, but still takes
  at least a half and hour per cam - often much
  more.
• One Linear pot is wired backwards in this picture.

10
Calibration Irregularity

• This showed up a problem with the earthquake
  restraint bolts that were engaging the girder
  during the motion. (We fixed this problem)

11
BBA Motion Control

• BBA corrections motions are typically 10 microns
  or less.
• Corrections are applied to all 33 girder
  simulateously through matlab software.

12
Undulator Pointing

• Can aim the x-rays by moving the entire undulaor
  line.
• Range is limited to about 1 mm (radius) at FEE.

13
Tolerance Zones

• Plan from 2004

14
Drift Rate

• lt 1micron/day motion relative to neighboring BPMs
• Prediction (2004) /- 0.5 microns/day from ground
  motion. (Weather also contributes a few-day time
  scales.)

15
Girder Motion from ADS

• ADS (stretched wire) measurements of programmed
  girder motion
• gt10 minutes per point

16
Hysteresis in Girder Motion

• Extremely sensitive beam-based measurements show
  up to 1 micron of hysteresis.
• We may implement a correction cycle, but further
  understanding is needed.

17
Summary

• Motion controls have been performing with
  accuracy and precision needed for BBA.
• New applications using motion controls are still
  being created.
• Preliminary indications of mechanical stability
  are favorable.