基于磁屏蔽原理改善LVDT静态性能的结构研究

线性差动变压器式位移传感器(LVDT)广泛应用各种直线测量系统中,针对其存在的线性度差、灵敏度不高的问题,首次基于磁屏蔽原理提出一种三层端盖的新结构,其中外侧端盖是磁屏蔽端盖。利用有限元的方法在ANSYS Maxwell建立LVDT仿真模型,在Maxwell Circuit Editor设计外部激励电路,进行联合仿真,通过静态和瞬态磁场的仿真研究。结果分析表明该新结构能将最大线性度从1.45%降低到0.13%,灵敏度提升20mv/mm。证明该结构能有效减少远离初级线圈两端的漏磁通,可以有效改善LVDT的线性度,同时灵敏度也有相应的提升。     

基于挤压油膜理论的二维电液压力伺服阀稳定性分析

针对飞机液压刹车系统,设计了一种2D电液压力伺服阀,以2D伺服螺旋机构为导阀,通过弹簧与主阀联动,采用直线位移传感器形成闭环位置反馈,精确控制出口压力;基于挤压油膜理论设计阀体结构,增大系统阻尼比,提高系统稳定性;在建立阀和油膜缓冲数学模型的基础上,仿真分析了主阀正开口量与弹簧变形量和主阀输出压力之间的关系,确保该阀具有良好的电流-压力特性;对初始系统、减小开环放大系数和增大系统阻尼比三种情况进行了稳定性仿真分析,验证了引入油膜阻尼缓冲设计的必要性。     

Volume change during the solidification of grey cast iron: its relation with the microstructural variation,comparison between experimental and theoretical analysis

The expansion/contraction during the solidification of grey cast iron was studied using Linear Variable Differential Transformer (LVDT). The experiments were conducted with and without melt treatment. Two types of inoculant used for melt treatment: ASSC (Si, Ca, Sr & Al) and MBZCAS (Si, Ca, Zr, Ba, Mn & Al). Microstructural investigations carried out to quantify the eutectic cells, undercooled graphite, primary austenite and secondary dendritic arm spacing (SDAS). It was found that the casting shows hardly any shrinkage during early solidification but in the eutectic region, the casting expands until the end of solidification. The measured and the calculated volume changes are close to one another, but the former shows more expansion. The addition of MBZCAS promotes more flake graphite, and ASSC does not increase eutectic cells much. In addition to that, it lowers the primary austenite fraction, promotes more eutectic growth, decreases undercooled graphite and SDAS. As a result, the volume expansion changes in the eutectic region.     

改进型LVDT在9E重型燃机上的应用

通过对使用在燃气轮机机组IGV(进口可转导叶)上LVDT的构造、作用和工作原理的分析,以及相关的试验研究,并在实际工程中进行应用,得出IGV开度范围所对应的LVDT铁芯的线性位移量只要符合线性范围表的要求就肯定可以正常应用的结论,同时规范了LVDT的安装应用方法、参数设置、设备校验过程,对实际工作具有指导意义。     

位移传感器仿真器设计

针对目前机载系统地面试验的要求,设计了一种简单、驱动能力强、通用性好的位移传感器仿真电路。运用模拟乘法器AD633完成基准载波信号幅度的调制,简化了硬件电路的复杂度;利用运算放大器的非线性反馈以及三极管的电流放大特性,大大提高了电路的带负载能力;使用基准电压和以及调节接口的设置提高了仿真电路的通用性。在某飞机飞行控制系统地面试验中的应用表明,该位移传感器仿真电路能够实现角位移传感器及线位移传感器信号的仿真,运行稳定、波形良好,有一定的推广意义。