高精度电磁标定力的产生及其特性分析

高精度标定力的产生是微推力高精度测量的关键之一。电磁力具有非接触、结构简单、容易控制等优势,成为微推力测量系统有效的标定力产生方法。针对微推力测量对于电磁标定力的性能要求,研究了磁铁与线圈之间相对位置变化对电磁力大小的影响关系,通过仿真计算得到了轴向距离、径向偏差、相对倾角变化下的电磁力输出特性:相对倾角、径向偏差不为0时,电磁力均会变大,且关于磁铁中心轴线具有对称性,沿轴向距离,电磁力先增大后减小。基于天平称重法,设计了可三维调节的电磁力测量装置,提出了轴向距离、径向偏差、相对倾角的归零调节方法;获得了电磁力较为完备的力学特性,通过分段拟合方法,解决了在较小标定力时相对误差较大的问题,确定了电磁力及电流的控制关系及相对位置变化范围;提出了不敏感角、不敏感径向偏差、不敏感轴向距离区间等新概念,为电磁力产生装置的性能表征提供了具体参数。

Generation and characteristic analysis of high accuracy electromagnetic calibration force

The generation of high accuracy calibration force is one of the key factors for high precision measurement of micro thrust. With the advantages of non contact, structure simplicity, control easiness and etc., electromagnetic force has become an effective method to generate calibration force in micro thrust measurement system. Aimed at the performance requirements of electromagnetic calibration force in micro thrust measurement, the effect of relative position changes between the magnet and the coil on the magnitude of the electromagnetic force is focused. The output characteristics of the electromagnetic force with vertical distance, radial deviation, relative angle changes are obtained by simulation: the electromagnetic force is symmetric along the central axis of the magnet and will become larger when the relative angle and the radial deviation are not zero; the electromagnetic force increases first and then decreases when axial distance increases. Based on the balance weighing method, a 3 D adjustable electromagnetic force measurement device is designed and a zero adjustment method of axial distance, radial deviation and relative angle is proposed. Relatively complete mechanical properties are obtained by the piecewise fitting method, the problem of large relative error in small calibration force output is solved. The control relationship between the electromagnetic force and the current is obtained, and the relative position variation range is specified. The new concepts such as insensitive angle, insensitive radial deviation, insensitive axial distance section and etc. are put forward, which provide specific parameters for performance characterization of the electromagnetic force generating device.