MMT Servos

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MMT Servos
Past
Present
Future.
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Detailed Information

• www.mmto.org/dclark/Reports
• SPIE 2008 poster, A Non-linear
  Disturbance-decoupled Elevation Axis Controller
  for the MMT
• IEEE American Controls Conference 2006,
  Developing Improved Servos for the Multiple
  Mirror Telescope

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The Original Servo for the 6.5m Telescope
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LM628 Servo Closed-loop
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The Elevation Axis Open Loop
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LM628 Tracking in Low Winds
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LM628 Tracking in High Winds
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A New Controller
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Control Design Workflow

• Use Simulink to design and analyze control system
  strategies using mathematical models of the
  telescope.
• Collect Open- and Closed-loop controller data
  with xPC Target for verification of simulation
  results.
• Use Simulink and Real Time Workshop to generate
  VxWorks executable code.

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An Example Open-loop Data Collection
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Simulate and Validate
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New Controller Tracking
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Tracking Jitter on the New Controller
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Wind Shake is NOT trivial!
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Looking ahead

• We have difficulties getting the xPC Target test
  system and the VxWorks deployment system to
  agree.
• Telemetry remains key to understanding the system
  performanceimproving the VxWorks systems
  capabilities will remain a priority.
• Work is ongoing to solve tracking jitter issues
  on elevation.

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Worthy of Mention

• Hardware has been moved to the VxWorks system to
  make the xPC Target machine and the deployment
  machine the same.
• Ultimately, we will want the development, test,
  and deployment to all be the same machineI am
  working on this through evaluation of real-time
  Linux using RTAI and drivers from the Comedi
  project

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Acknowledgements

• Keith Powell
• Tom Trebisky