Study On Combined Measurement Method Of MHD Angular Rate Sensor And MEMS Gyroscope

The angular rate sensor based on Magneto-hydrodynamics(referred to as MHD)has a broad bandwidth(up to 1KHz),low noise level,high precision,long life,impact resistance and other fine properties,which makes it suitable for in-flight measurement of high-resolution Earth observation system.Owing to the limitation of principle of the sensor,its low frequency(<2Hz)performance is poor,which greatly limits the application of it.In order to achieve the accurate measurement of low-frequency signals and the measurement bandwidth of 0-1KHz,this thesis adopts adding traditional angular rate sensor to do combined measurement.To meet the requirements of the miniaturization of payload space of the satellite,MEMS gyroscope is selected and the combined measurement method of the MHD angular rate sensor and MEMS gyroscope is studied.1.The thesis analyzes the principle of the MHD angular rate sensor and introduces performance parameter of the MEMS gyroscope,calculates the complex frequency domain models of them.A method for fast calculating the frequency response of angular velocity sensor is designed,whose effectiveness is verified by frequency response measurement.2.To compensate the low frequency error of the MHD angular rate sensor,taking into account the fluctuation of scale factor and phase with frequency changing,this thesis adopts the method of changing the complex frequency domain models of the MHD angular rate sensor,designs the phase compensation low pass filter with the function of extending low frequency which extends sensors' cut-off frequency from 2Hz to 0.05Hz.The thesis designs the phase compensation high pass filter which with the effect of the low frequency truncation,designs the fusion algorithm based on the aliasing filter which using the phase compensation high pass filter,fuses the signals of MHD angular rate sensor and MEMS gyroscope,solving the fluctuation problem of scale factor and phase with frequency changing.The single and mixing frequency experiments are carried,the experimental results show that without affecting the high frequency performance of MHD angular rate sensor,in range of 0-40Hz,the fluctuation of output amplitude is less than 1%,and the phase fluctuation is controlled within ±1°,achieving the measurement bandwidth of 0-1KHz.3.The thesis analyzes the noise sources of the combined system.Allan variance and classical power spectrum estimation are adopted to test and evaluate the noise level of the fused signals of MHD angular rate sensor and MEMS gyroscope.The experimental results show that the fusion algorithm has the ability of suppressing noise level.The angle random walk and bias stability are in the same magnitude of MEMS gyroscope,respectively N = 0.184°/s/(?),B = 29.2°/N;The rate noise density of fused signal is 0.0131°/s/(?),less than 0.0152°/s/(?) of MHD angular rate sensor.