Theoretical And Experimental Study On Magnetic Fluid Acceleration Sensors

Magnetic fluid is a novel functional material which shows both liquidity and paramagnetism.The study of the magnetic fluid acceleration sensors is about exploitation and utilization of the novel material which accords with the development trend of the acceleration sensors.At present,most of the research on magnetic fluid acceleration sensors focuses on the one-dimensional accelerometers,and there is lack of the research on the multi-dimensional accelerometers in domestic.In this paper,based on different restoring forces,two new types of two-dimensional magnetic fluid accelerometer models are presented,one is based on the first order levitation principle of magnetic fluid and the other is based on the second order levitation principle of magnetic fluid.In theory aspect,the calculation equation of the first order levitation principle of magnetic fluid is derived based on the surface stress tensor of magnetic fluid.The calculation equation of the second order levitation principle of magnetic fluid is derived based on the equivalent magnetic field model of the cylindrical permanent magnet.Based on the magnetic field generated by a single coil and the long straight solenoid,the inductance of the disk coil is calculated.The calculation equation of the inductance's variation in the coil and the output voltage of the accelerometer model are derived.The dynamic model of the magnetic fluid accelerometer is established and the dynamic response function is derived.The condition that the magnetic shield is required to be installed is analyzed,and the design of the magnetic shield is discussed.In simulation aspect,two simple methods to calculate the first order levitation force and the second order levitation force of magnetic fluid respectively are proposed.Based on the method the restoring force and the static output characteristics of the magnetic fluid accelerometer models are simulated.And both of the magnetic field distribution of the first order levitation sensor model with and without the magnetic shield are simulated.In experiment aspect,the first order levitation force and the second order levitation force of magnetic fluid with different parameters are experimental studied.The structural parameters of the disk coil are designed.The influences of the accelerometer models' static output characteristics caused by the signal source frequency,the parameters of the inertial mass,the distance of the disk coils,type of the magnetic fluid are experimental studied.The hysteresis and repeatability of the magnetic fluid accelerometer models are measured and analyzed.The measurement error of magnetic fluid accelerometers under two-dimensional acceleration is experimental studied.The dynamic characteristics of the accelerometer models are studied and compared with the simulation results.The performance of the accelerometer models before and after the installation of magnetic shielding is studied.On the basis of the above research,the innovative conclusions are shown as follows:(1)The simulation calculation method proposed in this paper is simple and easy to calculate the first order levitation force of magnetic fluid exerted on an arbitrary non-magnetic object,and the simulation results are in good agreement with the experimental results;(2)The second order levitation force of magnetic fluid calculated by the double image method are in good agreement with the experimental results when the permanent magnet is a bit far away from the magnetic fluid's boundary;(3)The magnetic fluid with different carrier fluid shows different saturation magnetization,density,relative magnetic susceptibility and viscosity,which affects on both static and dynamic performance of the accelerometer models;the experimental results show that the engine oil-base magnetic fluid has better linearity and sensitivity than the water-based magnetic fluid and the kerosene-based magnetic fluid;and in the aspects of dynamic characteristics,the engine oil-base magnetic fluid has the the smallest overshoot and oscillation times;(4)Either of the accelerometer model based on the first order levitation principle of magnetic fluid or based on the second order levitation principle of magnetic fluid has its merits and demerits in static performance,the first order levitation sensor model is better than the second order levitation sensor model in linearity,but the the second order levitation sensor model has its advantages in sensitivity,hysteresis and repeatability;however,the dynamic characteristics of two models is similar.(5)Compared with the accelerometer model based on the second order levitation principle of magnetic fluid,the accelerometer model based on the first order levitation principle of magnetic fluid has smaller size and lower cost with magnetic shield.