水平磁性液体微压差传感器的理论及实验研究

发布时间：2018-08-15 15:03

【摘要】：磁性液体是一种兼具固体材料的磁性和液体材料的流动性的新型纳米功能材料,其在磁场梯度作用下的表面不稳定性和独有的二阶浮力使得其在传感器领域有着广阔的应用前景。目前我国的高精密微压差传感器的制造水平和工艺与国外(10-3a量级)差距很大,这一问题亟需通过采用新材料、新工艺、新结构的方式解决。本文以煤油基、机油基、水基、酯基磁性液体为基础,利用磁性液体的二阶浮力原理,提出了一种电感式水平磁性液体微压差传感器的模型。在理论方面,推导了该模型中复合磁芯永久磁铁与回复力磁铁之间的回复力公式,给出了复合磁芯的下沉公式,得出了水平磁性液体微压差传感器的耐压能力与复合磁芯和透明亚克力管之间单边间隙的数学关系,计算了复合磁芯的位移与线圈电感变化之间的函数关系,推出了水平磁性液体微压差传感器静态测量时的输入输出特性和动态测量时的二阶系统传递函数;在结构设计方面,针对水平磁性液体微压差传感器的敏感元件和转换元件,提出了不同的设计模型,通过理论分析、仿真研究和实验测量等手段确定了最终各元件的参数;在仿真方面,利用ANSYS有限元分析软件对永久磁铁间的回复力、复合磁芯在透明亚克力管中的下沉距离以及磁性液体环的耐压值进行了仿真分析,同时运用MATLAB软件对水平磁性液体微压差传感器的尺寸参数进行了优化设计,对二阶水平磁性液体微压差传感器系统在阶跃压强作用下的动态输出特性进行了仿真分析;在实验方面,给出了永久磁铁之间回复力的线性拟合公式,确定了水平磁性液体微压差传感器的最终量程范围,深入研究了水平磁性液体微压差传感器静态测量时的输入输出关系,并探究了该传感器的线性度、灵敏度、精度、分辨率、迟滞、重复性和稳定性,同时对不同基载液(即不同粘度)的磁性液体对水平磁性液体微压差传感器动态输出特性的影响进行了实验研究,并将实验结果与仿真结果相比较,分析了理论值和实验值存在差异的原因。得出的创新性结论如下:(1)设计了一种新型的水平磁性液体微压差传感器,该传感器的量程范围士1000Pa,精度△Xmax= 10Pa,线性度ef=2.5%、灵敏度S=0.1mV/Pa、分辨率0.6%F.S.,迟滞 δH = ±1.25%;(2)水平磁性液体微压差传感器的量程范围主要由以下两方面因素共同决定:一是磁性液体密封环的密封耐压能力;二是永久磁铁回复力的线性区间所允许的复合磁芯位移量。水平磁性液体微压差传感器最终的量程范围由二者中较小者决定;(3)基于二阶浮力原理,根据仿真结果给出了复合磁芯吸附磁性液体后在透明亚克力管中下沉距离的经验公式,公式表明复合磁芯的下沉距离与磁芯重量、磁性液体饱和磁化强度有关,这为研究水平磁性液体微压差传感器中磁性液体密封环的耐压能力提供了理论依据;(4)磁性液体粘度对水平磁性液体微压差传感器静态性能的影响可以忽略不计,但对水平磁性液体微压差传感器的上升时间、超调量、振荡次数、稳定时间等动态参数的影响较大;(5)基于所设计的水平磁性液体微压差传感器,提出了静态测量时的非线性规划模型,并进行了仿真分析和实验研究,实验值和理论值基本一致。并给出了理想状态下的水平磁性液体微压差传感器的尺寸参数最优值;(6)水平磁性液体微压差传感器中的复合磁芯可以视为质量块,永久磁铁之间的回复力可以视为弹簧项,磁性液体与透明亚克力管之间的牛顿内摩擦力可以视为阻尼项,由此可知水平磁性液体微压差传感器可以等效成二阶动态系统。以此为基础推导了水平磁性液体微压差传感器的传递函数,分析了各参数对水平磁性液体微压差传感器动态性能的影响,为今后水平磁性液体微压差传感器应用于动态测量时的参数设计提供了理论依据。
[Abstract]:Magnetic fluid is a new kind of nano-functional material with both magnetic properties of solid materials and fluidity of liquid materials. Its surface instability under magnetic field gradient and unique second-order buoyancy make it have broad application prospects in the field of sensors. At present, the manufacturing level and technology of high-precision micro-differential pressure sensors in China This problem needs to be solved by using new materials, new technology and new structure. Based on kerosene-based, oil-based, water-based and ester-based magnetic fluids, a model of inductive horizontal magnetic fluids micro-differential pressure sensor is proposed by using the second-order buoyancy principle of magnetic fluids. The restoring force formula between permanent magnet with composite core and restoring force magnet in the model is deduced. The sinking formula of composite core is given. The mathematical relationship between the pressure resistance of horizontal magnetic fluid micro-pressure differential sensor and the unilateral gap between composite core and transparent acrylic tube is obtained. The displacement of composite core and the coil electricity are calculated. The input-output characteristic and the second-order system transfer function of the horizontal magnetic fluid micro-differential pressure sensor in static and dynamic measurement are deduced from the functional relationship between the inductance changes. In the aspect of simulation, the restoring force between permanent magnets, the sinking distance of composite core in transparent acrylic tube and the pressure resistance value of magnetic fluid ring are simulated and analyzed by ANSYS finite element analysis software, and the horizontal magnetism is also analyzed by MATLAB software. The dimension parameters of the liquid micro-differential pressure sensor are optimized and the dynamic output characteristics of the second-order horizontal magnetic liquid micro-differential pressure sensor system under step pressure are simulated and analyzed. In the final range of measurement, the relationship between input and output in the static measurement of the horizontal magnetic fluid micro-differential pressure sensor is deeply studied, and the linearity, sensitivity, precision, resolution, hysteresis, repeatability and stability of the sensor are explored. The experimental study on the dynamic output characteristics is carried out and the reasons for the difference between the theoretical and experimental values are analyzed by comparing the experimental results with the simulation results. The innovative conclusions are as follows: (1) A new type of horizontal magnetic fluid micro-differential pressure sensor is designed. The measuring range of the sensor is 1000Pa, and the precision is {Xmax=10Pa,} line. Property EF = 2.5%, sensitivity S = 0.1 mV/Pa, resolution 0.6% F.S., hysteresis Delta H = + 1.25%; (2) The range of the horizontal magnetic fluid micro-differential pressure sensor is mainly determined by the following two factors: one is the sealing resistance of the magnetic fluid seal ring; the other is the displacement of the composite core allowed by the linear range of the permanent magnet's resilience. Based on the second-order buoyancy principle, the empirical formula of the sinking distance of the composite core adsorbed magnetic fluid in a transparent acrylic tube is given according to the simulation results. The formula shows the sinking distance of the composite core and the weight of the core, and the saturation magnetism of the magnetic fluid. The results provide a theoretical basis for studying the pressure resistance of the magnetic fluid sealing ring in the horizontal magnetic fluid micro-differential pressure sensor. (4) The influence of the viscosity of the magnetic fluid on the static performance of the horizontal magnetic fluid micro-differential pressure sensor can be neglected, but the rise time, overshoot and oscillation of the horizontal magnetic fluid micro-differential pressure sensor can be neglected. (5) Based on the designed horizontal magnetic fluid micro-differential pressure sensor, a nonlinear programming model for static measurement is proposed, and the simulation analysis and experimental research are carried out. The experimental and theoretical values are basically the same. (6) The composite core in the horizontal magnetic fluid micro-differential pressure sensor can be regarded as a mass block, the restoring force between permanent magnets can be regarded as a spring term, and the Newtonian internal friction between the magnetic fluid and the transparent acrylic tube can be regarded as a damping term. Based on this, the transfer function of the horizontal magnetic fluid micro-differential pressure sensor is deduced, and the influence of various parameters on the dynamic performance of the horizontal magnetic fluid micro-differential pressure sensor is analyzed. The theoretical basis is provided for the parameter design of the horizontal magnetic fluid micro-differential pressure sensor when it is applied to the dynamic measurement in the future.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP212

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