Main axis control of the Large Millimeter Telescope

David R. Smith; Kamal Souccar

doi:10.1117/12.857501

4 August 2010 Main axis control of the Large Millimeter Telescope

David R. Smith, Kamal Souccar

Proceedings Volume 7733, Ground-based and Airborne Telescopes III; 77332M (2010) https://doi.org/10.1117/12.857501
Event: SPIE Astronomical Telescopes + Instrumentation, 2010, San Diego, California, United States

Abstract

The initial operation of the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT) main axis servo system showed promising results, with subarcsecond RMS performance even without a complete drive system. Since that time, there has been substantial progress in the commissioning of the system. For example, the alignment and grouting of the elevation axis gear rims is completed and all motors have been installed. This has allowed full-speed operation in both axes and has enabled some tuning of the servo system. The digital control architecture of the LMT allows direct measurement of the frequency response function of the system. Further, it allows the rate loop and position loop to be configured either as a classical proportional-integral (PI) controller or as a model-based (e.g., LQG) state-space controller. Finally, the architecture permits additional special-purpose control features to be implemented, including friction compensation and lookup table feedforward to reduce nonlinear effects. The measured FRF results are presented, and have been applied to tuning of the control system, with a resulting improvement in performance. Results are presented for the LMT main axis slewing, pointing, and tracking performance. Additionally, results are presented from initial experiments in applying lookup table feedforward to improve performance in crossing joints in the azimuth track.

Citation Download Citation

David R. Smith and Kamal Souccar "Main axis control of the Large Millimeter Telescope", Proc. SPIE 7733, Ground-based and Airborne Telescopes III, 77332M (4 August 2010); https://doi.org/10.1117/12.857501

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KEYWORDS

Telescopes

Servomechanisms

Control systems

Space telescopes

Astronomical telescopes

Computer programming

Laser range finders

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