6 February 2018 Design, development, and validation of a segment support actuator for the prototype segmented mirror telescope
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Abstract
Segmented mirror telescopes (SMT) are built using several small hexagonal mirrors positioned and aligned by the three actuators and six edge sensors per segment to maintain the shape of the primary mirror. The actuators are responsible for maintaining and tracking the mirror segments to the desired position, in the presence of external disturbances introduced by wind, vibration, gravity, and temperature. The present paper describes our effort to develop a soft actuator and the actuator controller for prototype SMT at Indian Institute of Astrophysics, Bangalore. The actuator designed, developed, and validated is a soft actuator based on the voice coil motor and flexural elements. It is designed for the range of travel of ±1.5  mm and the force range of 25 N along with an offloading mechanism to reduce the power consumption. A precision controller using a programmable system on chip (PSoC 5Lp) and a customized drive board has also been developed for this actuator. The close loop proportional-integral-derivative (PID) controller implemented in the PSoC gets position feedback from a high-resolution linear optical encoder. The optimum PID gains are derived using relay tuning method. In the laboratory, we have conducted several experiments to test the performance of the prototype soft actuator as well as the controller. We could achieve 5.73- and 10.15-nm RMS position errors in the steady state as well as tracking with a constant speed of 350  nm/s, respectively. We also present the outcome of various performance tests carried out when off-loader is in action as well as the actuator is subjected to dynamic wind loading.
© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
Prasanna G. Deshmukh, Amaresh Mandal, Padmakar Singh Parihar, Dayananda Nayak, Deepta Sundar Mishra, "Design, development, and validation of a segment support actuator for the prototype segmented mirror telescope," Journal of Astronomical Telescopes, Instruments, and Systems 4(1), 014005 (6 February 2018). https://doi.org/10.1117/1.JATIS.4.1.014005 . Submission: Received: 3 July 2017; Accepted: 8 January 2018
Received: 3 July 2017; Accepted: 8 January 2018; Published: 6 February 2018
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