Study On Low Noise Extraction Method For Weak Signal Of MHD Angular Velocity Sensor

The micro-angular vibration of spatial structure is one of the important factors limiting the spatial resolution of ground observation system and the attitude stability of platform.Compared with conventional gyroscopes,magnetic fluid dynamics angular velocity sensors have the advantages of sub-radian measurement accuracy and kHz bandwidth,especially for the measurement of micro-angular vibration of spatial structures.Because the output signal of the sensitive components inside the MHD angular velocity sensor is weak and susceptible to noise interference,in order to ensure the low noise characteristics of the sensor,the following design methods for the low noise extraction of weak signal of the sensor are studied:Firstly,the low-noise design method for the MHD angular velocity sensor model is studied.A direct-coupled amplifying circuit that uses the parallel method of active discrete devices to improve the noise performance of the integrated operational amplifier is designed.Noise measurement experiments have shown that the equivalent input noise of the direct coupled amplifier circuit is of the order of (?) magnitude.Secondly,a weak signal extraction method based on magnetic field modulation is proposed,which solves the problem that the amplifying circuit based on direct coupling is susceptible to interference from the 1/f noise of operational amplifier and other low frequency noise.It is proposed to realize the amplitude modulation of the output signal of MHD angular velocity sensor by magnetic field modulation.Finally,the magnetic field generator of MHD angular velocity sensor is designed to generate a stable alternating magnetic field.A magnetic field drive device with automatic gain can be designed to solve the problem that the amplitude of alternating magnetic field is susceptible to external interference instability.The system test shows that the magnetic field frequency generated by the solenoid is 10.6kHz,the effective value of the magnetic induction intensity is 16.9mT,which satisfies the theoretical design requirements and provides a stable high frequency carrier signal is provided for weak signal extraction based on magnetic field modulation.