Low Frequency Extension Design Of Angular Velocity Sensor Based On Magnetohydrodynamics

The angular velocity sensor based on magnetohydroynamics(MHD)has the characteristics of low noise,wide frequency band,and impact resistance,which makes it suitable for the measurement of micro-angular vibration of wide-band,low-amplitude spatial structures.Due to the poor performance of the MHD sensor is low-frequency(<1Hz)bandwidth of micro-angle vibration measurement,it needs to be combined with other low-frequency gyroscopes to measure low-frequency bandwidth signals,which greatly limits the application of it.In order to achieve accurate measurement of lowfrequency(<1Hz)micro-angle vibration,this paper studies the improvement of the mechanical structure of the MHD angular velocity sensor,adding multiple magnetic fluid pumps at the edge of the fluid channel to achieve the formation of a stable radial flow velocity in the sensing fluid ring.Enhance the Coriolis effect induced by the radial flow velocity at low frequency,and realize the full bandwidth signal measurement of the MHD angular velocity sensor.The main work of this paper is as follows:(1)The working principle and characteristics of the MHD angular velocity sensor are analyzed,and the simplified model of the simple fluid loop MHD sensor is analyzed.In this article,the MHD sensor with Coriolis force effect is called C-MHD(CoriolisMHD)angular velocity sensor.The radial flow velocity introduced by the sensing ring induces Coriolis acceleration,enhances the circumferential flow velocity of the conductive fluid to cut the magnetic line of induction,and improves the low-frequency signal detection capability of the sensor.The derivation of the simplified model proves the feasibility of introducing radial velocity to expand the low-frequency bandwidth.(2)In order to improve the stable radial flow velocity in the fluid ring of the MHD sensor,the C-MHD angular velocity sensor was newly designed.Three symmetrically distributed magnetohydrodynamic pumps were constructed at the edge of the fluid channel to enhance the radial velocity in the fluid ring.The magnetic circuit structure,magnetic field distribution and flow field of DC MHD pump of C-MHD sensor model are simulated and analyzed by COMSOL,optimize the structure of the sensor,and the cylindrical permanent magnet at the magnetic fluid pump is replaced by an arc permanent magnet.Compared with the circular permanent magnet,the area of the magnetic induction area of the arc magnet pump channel is increased by 38.36%.(3)In order to verify the effect of increasing the radial velocity distribution and expanding the low-frequency bandwidth of the C-MHD sensor,the fluid motion of the sensor fluid ring in the low and high frequency bands after the introduction of radial velocity is analyzed.The MHD module of FLUENT is used to simulate the electromagnetic field and flow field coupling of the model,and the frequency domain simulation experiment is carried out.In the simulation results,the amplitude-frequency characteristic curve of the sensor can verify the effectiveness of the radial flow velocity to expand the low-frequency bandwidth of the sensor.(4)According to the structural parameters and dimensions of the sensor obtained by the simulation,the mechanical structure of the corresponding sensor was designed,the parts,magnetic poles were assembled and the conductive fluid was filled to complete the prototype of the C-MHD sensor,and the frequency domain response and time domain were performed on the angular velocity platform.The experimental results prove that the sensor can output the detected angular velocity signal,but the compensation current required at the frequency(<1Hz)is higher than the simulated value,and there is an error effect between the amplitude-frequency characteristic curve of the prototype and the numerical simulation result.