Special Section on Ground-Based/Airborne Telescopes and Instrumentation

Design and development of telescope control system and software for the 50/80  cm Schmidt telescope

[+] Author Affiliations
Tripurari S. Kumar

Indian Institute of Technology Bombay, Systems and Control Engineering, Mumbai 400076, India

Aryabhatta Research Institute of Observational Sciences, Electronics Section, Nainital 263129, India

Ravi N. Banavar

Indian Institute of Technology Bombay, Systems and Control Engineering, Mumbai 400076, India

Opt. Eng. 52(8), 081607 (May 31, 2013). doi:10.1117/1.OE.52.8.081607
History: Received October 31, 2012; Revised March 21, 2013; Accepted May 2, 2013
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Abstract.  We describe the details of telescope control system design for the 50/80cm Schmidt telescope at the Aryabhatta Research Institute of Observational Sciences. The overall control hardware architecture features a distributed network of microcontrollers over controller area network for interfacing the feedback elements and controlling the actuators. The main part of the hardware is a controller whose final objective is to provide position control with 10 arcsec accuracy and velocity control with 1arcsec/s accuracy. For modeling and simulation, the telescope parameters were experimentally determined. A linear proportional integral (PI) controller was designed for controlling the twin-motor drive mechanism of the telescope axes. The twin-motor drive is provided with differential torque for backlash-free motion reversal. This controller is able to maintain negligible rms errors at all velocities. At higher speeds over 2deg/s, the PI controller performs with peak errors less than 1%. Whereas at fine speeds, depending upon the preload on bearings, limit cycles are exhibited due to nonlinear friction posing control related problems. We observed that the effect of nonlinear friction dynamics can be reduced by reducing the preload on the drive bearings and the peak errors at fine speeds using a linear controller can be maintained within 25%.

© 2013 Society of Photo-Optical Instrumentation Engineers

Citation

Tripurari S. Kumar and Ravi N. Banavar
"Design and development of telescope control system and software for the 50/80  cm Schmidt telescope", Opt. Eng. 52(8), 081607 (May 31, 2013). ; http://dx.doi.org/10.1117/1.OE.52.8.081607


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