LCLS Undulator Support/Mover System Testing Status

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LCLS Undulator Support/Mover System Testing
Status

• Jeff T. Collins

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Support/Mover System Testing
History

• We Assembled a Breadboard Undulator
  Support/Mover System Using Existing Parts at the
  Early Stages of the Design Process
• To Get an Early Start on Motion Testing, we
  Specified, Procured and Installed a Very
  Accurate Measurement System for the Breadboard
  Support/Mover System
• A Labview-Based Data Acquisition and Control
  System was Developed In-House for Command and
  Control of all Motors with Feedback and
  Monitoring from the Measurement System
• The Breadboard System was Used to Learn How
  to Control and Characterize the Performance of
  the Motion System
• Results from Numerous Tests were Used as
  Feedback for Refinement of the Design Process.
  Problem Areas have been Identified and Solutions
  have Been Implemented in the Actual
  Support/Mover System Design
• Measurement Results are Very Encouraging with
  Overall Excellent Repeatability

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Support/Mover System Testing
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Support/Mover System Testing
Our Present Breadboard Lacks Many Features
that the Prototype will Include

• Does not have Expanded Wedge on Upstream
  Double CAM Mover
• Aluminum Frame instead of Steel Frame
• Bearing Surfaces are not Hardened or Polished
• 1001 Gearbox instead of 2501 Gearbox
• Less Precise Rotary Potentiometers
• Only Four Linear Potentiometers
• Lack a Precision Temperature-Controlled
  Environment

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Support/Mover System Testing
Salient Support/Mover System Physics Requirements

• Quadrupole Motion Positioning Repeatability 7
  µm
• Short-Term (1 h) BPM and Quad Stability 2 µm
• Long-Term (24 h) BPM and Quad Stability 5 µm
• Horiz. Segment Pos. Repeatability in Roll-Away
  Cycle 10 µm
• Vert. Segment Pos. Repeatability in Roll-Away
  Cycle 5 µm
• Quad Transverse Position Change in Roll-Out
  Condition 25 µm
• Quad Position Reproducibility after Roll-Away
  Cycle 2 µm
• BPM Transverse Position Change in Roll-Out
  Condition 25 µm
• BPM Position Reproducibility after Roll-Away
  Cycle 2 µm

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Support/Mover System Testing
System Measurement Devices

• Five Keyence Laser Displacement Sensors (0.05
  micron repeatability). Two at each end
  measuring X and Y Displacement at the Quadrupole
  Position, and one located mid-plane of the
  Undulator on one side to measure Roll.
• Four Linear Potentiometers (1-2 micron
  repeatability) measuring X and Y Displacements
  on one side of the Girder located near the CAM
  Movers.

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Support/Mover System Testing
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Support/Mover System Testing
CAM Mover System Degrees of Freedom

• X-Translation (Inboard or Outboard Translation)
• Y- Translation (Up or Down Translation)
• Pitch Motion (Upstream or Downstream Pitch)
• Roll Motion (Inboard or Outboard Roll)
• Yaw Motion (From Either End or Both Ends)

• Notes
• The System can Move with Five Degrees of Freedom
  using any Combination of these Motions.
• The Z-Dimension is Restricted but not
  Constrained via the Recessed Flat on the Single
  CAM Mover.

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Support/Mover System Testing
CAM Mover Calibration Procedure

1. Rotate one CAM through a Full Revolution
2. Measure Displacement as a function of Angular
   Position using either the Keyence Sensors or the
   Linear Potentiometers
3. Plot the Displacement as a function of Angular
   Position
4. Curve Fit the Data to Locate the Zero Position
5. Repeat this Process for each of the Five CAM
   Movers

Problems with this Approach

• Rotating one CAM introduces Pitch, Roll, and Yaw
  into the System
• These Motions add Stress into the Girder causing
  Distortion
• These Distortions become part of the Calibration
• The Calibration is not Decoupled from the Girder
• The existing Rotary Potentiometers have 1 of
  Backlash adding to
• Calibration Uncertainty

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Support/Mover System Testing
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Case 1 X-Translation /- 1.5 mm Cyclic Motion
Repeatability
Location Laser Displacement Sensors Linear Potentiometers
Upstream X 2.5 µm 1.5 µm
Upstream Y 1.0 µm 4.0 µm
Downstream X 2.0 µm 2.5 µm
Downstream Y 0.5 µm 4.0 µm
Target Repeatability lt /- 7.0 µm
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Support/Mover System Testing
Infrared Image Prior to Motor Operation,
Downstream End Double CAM Mover with Pedestal
Base
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Support/Mover System Testing
Infrared Image Prior to Motor Operation,
Downstream End Double CAM Mover with Pedestal
Base
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Support/Mover System Testing
Infrared Image After Motor Operation, Downstream
End Double CAM Mover with Pedestal Base, Motor on
for Approximately 2 Hours
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Case 2 Y-Translation /- 1.5 mm Cyclic Motion
Repeatability
Location Laser Displacement Sensors Linear Potentiometers
Upstream X 1.0 µm 2.5 µm
Upstream Y 2.5 µm 1.0 µm
Downstream X 0.5 µm 4.0 µm
Downstream Y 1.5 µm 1.0 µm
Target Repeatability lt /- 7.0 µm
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Case 3 Roll /- 1.5 mm Cyclic Motion
Repeatability
Location Laser Displacement Sensors Linear Potentiometers
Upstream X 1.0 µm 2.0 µm
Upstream Y 0.5 µm 0.5 µm
Downstream X 0.5 µm 4.0 µm
Downstream Y 0.5 µm 1.5 µm
Target Repeatability lt /- 7.0 µm
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Case 4 Upstream Pitch /- 1.5 mm Cyclic Motion
Repeatability
Location Laser Displacement Sensors Linear Potentiometers
Upstream X 1.0 µm 2.0 µm
Upstream Y 1.5 µm 1.0 µm
Downstream X 0.5 µm 2.0 µm
Downstream Y 0.5 µm 0.5 µm
Target Repeatability lt /- 7.0 µm
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Case 5 Both Ends Yaw 1.5 mm in Opposite
Directions
Location Laser Displacement Sensors Linear Potentiometers
Upstream X 15.0 µm 2.5 µm
Upstream Y 5.0 µm 2.5 µm
Downstream X 25.0 µm 2.5 µm
Downstream Y 2.5 µm 5.0 µm
Target Repeatability lt /- 7.0 µm
Note
Yaw Motion is Incidental and is Not Required for
Actual Operation.
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Support/Mover System Testing
CAM Mover System Observations

• All Motions that allow the CAM Bearings to Freely
  Rotate (X-Translation, Y-Translation, and Roll)
  are Repeatable to better than /- 2.5 microns at
  the Quadrupole Position (Target Repeatability lt
  /- 7.0 microns).
• Though Pitch Motion is Overconstrained the
  Bearing on the Single CAM Mover only needs to
  Slip a few microns Across the Recessed Flat and
  therefore the Motion still Shows Excellent
  Repeatability.
• Yaw Motion is very Overconstrained and therefore
  the Bearing on the Single CAM Mover Must Slip
  Hundreds of microns Across the Recessed Flat.
  This Slippage, the Process of Overcoming Static
  Friction, Distorts the Girder Causing Large
  Repeatability Errors.

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Support/Mover System Testing
CAM Mover System Observations

• Some Repeatability Error is Added to the Linear
  Potentiometers
• from Sliding Across the Contact Surfaces causing
  Bending of the
• Sensor Arms.
• The Ball Bearing Tips of the Linear
• Potentiometers Wore Flat after Many
• Cycles from Sliding Across the Contact
• Surfaces.

1. From a Cold Start, Heat from the Motors can Cause
   Tens of Microns of Change from the Original Start
   Position.

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Undulator Roll-Away Cycle Testing
Undulator Segment Roll-Away Cycle /- 10 mm
Cyclic Translation
Note Translation Stage Motions were Driven
Purely by Motor Steps with no Feedback from the
Linear Encoders. Many Changes will be Made to
these Stages for the Actual Prototype.
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Implemented Changes for the Actual Prototype

1. Improved Translation Stage Design for Roll-Away
   Cycle

• Stages will be Preloaded to Decrease Play in the
  Slides
• Gearboxes Replaced with GAM Angular Gearboxes
  with Backlash Less than 15 arcsec. (Compared to
  40 arcsec. on Existing Stages)
• Table Length Increased from 6 to 8 and Ball
  Bearing Separation is Increased Accordingly
• Size of all Mounting Holes have been Increased
  for Added Stiffness

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Implemented Changes for the Actual Prototype

1. Steel Girder Replaces the Aluminum Girder.

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Implemented Changes for the Actual Prototype

• Expanded Wedge on the Upstream Double CAM Mover
  for
• Increased Stability.

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Implemented Changes for the Actual Prototype

• Inverted Wedge for the Single CAM Mover to
  Constrain Z-Dimension
• Movement.

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Implemented Changes for the Actual Prototype

1. Two Side-by-Side Bearings for the Single CAM
   Mover to Eliminate Slip across the Bearing
   Surface.

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Implemented Changes for the Actual Prototype

• Spherical Bearings for Both of the Double CAM
  Movers to allow
• Rotational Play on these Bearings. The Single
  CAM Mover will
• still use a Roller Bearing. High Precision
  Bearings will Replace the
• Existing Standard Bearings.

Note Changes to the Bearings on the Double CAM
Movers, the Inverted Wedge Bearing Surface,
and the Side-by-Side Bearings on the Single CAM
Mover will Eliminate Bearing Slip and will
Allow the Girder to Pivot about the Single CAM
Mover Contact Surface.
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Implemented Changes for the Actual Prototype

1. The Addition of Four more Linear Potentiometers
   to Provide X and Y Displacement Information at
   the Four Corners of the Girder near the CAM
   Movers.

Note With Eight Linear Potentiometers Defining
the Girder Position, the Effects of Girder
Distortion can be Decoupled from the CAM Mover
Calibrations allowing Precise CAM Mover
Calibration.
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Implemented Changes for the Actual Prototype

1. Replace the 1001 Gearboxes with 2501 Gearboxes.
   This will Eliminate the need for Brakes on the
   Motors, add Better Resolution to the System, and
   Simplify Control System.
2. Replace existing Rotary Potentiometers (1
   Backlash) with more Precise Rotary Potentiometers
   with better than 0.1 Backlash. This will
   Improve CAM Mover Calibration.
3. All Bearing Surfaces shall be Hardened and Highly
   Polished. This should add to Long-Term System
   Stability and Repeatability.

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Support/Mover System Testing
Conclusions

• The LCLS Undulator Support/Mover Tests on our
  Breadboard are Very Encouraging with Overall
  Excellent Repeatability.
• We have Identified Problem Areas and have
  Implemented Solutions that will Improve
  Performance.
• Testing To-Date has Provided Valuable Information
  on System Dynamics, Environmental Influences,
  Calibration Procedures, and Feedback and Control
  Algorithms.
• Similar, but more in-depth, Tests shall be
  Performed on the Actual Prototype once the System
  has been Assembled.