YANG Shi-hai. Detection and suppression of oil pad nonlinear disturbance for large optical telescope [J]. Editorial Office of Optics and Precision Engineering, 2013,21(2): 408-415
YANG Shi-hai. Detection and suppression of oil pad nonlinear disturbance for large optical telescope [J]. Editorial Office of Optics and Precision Engineering, 2013,21(2): 408-415 DOI: 10.3788/OPE.20132102.0408.
Detection and suppression of oil pad nonlinear disturbance for large optical telescope
This paper explores the effect of nonlinear disturbance of a static pressure oil pad in an optical astronomical telescope on the tracking accuracy. Firstly
the causes of oil pad disturbance are analyzed and the frequencies of nonlinear disturbances are measured accurately with accelerometers and an encoder. By analysis of the vibration curve of the accelerometer
the position curve and Fast Fourier Transfer(FFT) curve of the encoder when the oil pad is turning on or turning off
it points out that the vibration of oil pad is narrow band interference. Then
a Notch filter is proposed to suppress the oil pad disturbance by setting the central frequency at the main disturbance frequency. The design process of the proposed method is discussed in detail.The bode diagram and the zero-pole map of Notch filter are given. When oil film thickness needs to be changed
the Notch frequency band can be adjusted flexibly by changing the parameters of Notch filter. Finally
the control system with Notch filter is implemented and filtering results are shown. Simulation and experimental results of tracking and pointing on a 2.5 m astronomical optical telescope indicate that the tracking precision of the azimuth system is 0.083 7″RMS and 0.571″PV by measuring and eliminating the main noise at 0.825 Hz .As comparing with pressure fluctuation attenuation devices
the proposed method shows the advantages of convenience
flexibility and good universality.
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