28 July 2014 Analysis, testing, and control of telescope's high-precision drive system in low-temperature environment
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Antarctic is perfect site for astronomic observatory. But Antarctic also challenge the telescope design because of low temperature. The low temperature can impact characterization of telescope control system, especially for drive system. The following phenomenon can be produced due to low temperature. 1. The viscosity of grease will increase. 2. The clearance of bearing and gear will decrease. These two factors can lead to the increase in load torque of drive system with temperature drop. This would cause the bad tracking accuracy and low speed creeping. In order to overcome the impact of low temperature and improve the telescope’s track accuracy. In this paper, we describe some methods to overcome the effect of low temperature. First, the motor’s electromagnetism and lubrication in low temperature are analyzed. It shows that motor’s electromagnetism is little affected by temperature if the suitable material is selected. But the characterization of grease change dramatically with temperature. Second, the other lubricant material, solid lubricant, instead of lubricating grease is proposed. Contrasting experiment on two lubricant material proved that the solid lubricant is better than lubricating grease in low temperature environment. Third, besides the mechanical solution, a method from control point view is proposed to reduce the temperature influence. In this paper, the friction feedforward algorithm is used to compensate the torque change. Laboratory testing results will be presented verifying that friction feedforward can increase the tracking accuracy in low temperature environment.
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Fu-Jia Du, Fu-Jia Du, Jian Zhang, Jian Zhang, Hai-Kun Wen, Hai-Kun Wen, } "Analysis, testing, and control of telescope's high-precision drive system in low-temperature environment", Proc. SPIE 9151, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, 91513B (28 July 2014); doi: 10.1117/12.2054422; https://doi.org/10.1117/12.2054422

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