Directionally Controllable Squeeze Film Damper Using Liquid Crystal

液晶（LC）是一种高功能流体，其表观粘度可受外加电场或磁场的影响而变化。LC是一种均质液体，其牛顿粘度可随外加电场或磁场强度而变化。LC具有表观粘度变化范围广、可控性好、响应时间快等吸引人的特点，这使得LC在机械设备上的应用进行了各种尝试。挤压膜阻尼器（SFD）作为旋转系统的阻尼装置已得到广泛的应用。SFD的阻尼特性通常由润滑剂的粘度和阻尼器的间隙决定。Satio和Kobayashi指出，柔性转子的各种旋转模式都存在支承阻尼的最优值。本文研究了一种以LC为润滑剂的可控SFD，该SFD可以在水平方向和垂直方向上产生各向异性阻尼力。一般情况下，柔性轴的旋转轨道不是圆形而是椭球轨道，因此，通过单独控制阻尼力可以有效地减小各转速下柔性轴的旋转幅值。将放置在SFD中的一对控制润滑油粘度的电极分为水平方向和垂直方向，并对其定向可控性进行了实验研究。在此基础上，构建了基于人工神经网络的自适应控制系统，并对其性能进行了研究。

Liquid crystal (LC) is known as one of highly functional fluids whose apparent viscosity can be varied by an externally applied electric or magnetic field. LC is a homogeneous liquid and its Newtonian viscosity can be varied by the applied electric or magnetic field strength. The attractive characteristics of LC are the wide range of variation of apparent viscosity, the controllability and quick response time, which leads to make various attempts of applying LC to mechanical equipments.A squeeze film damper (SFD) has been widely used as a damping equipment of rotating systems. The damping characteristics of a SFD are generally governed by the viscosity of lubricant and the clearance of the damper. Satio and Kobayashi pointed out the existence of the optimum value of the supporting damping for every whirling mode of a flexible rotor.This research treats a controllable SFD that uses LC as a lubricant which can produce anisotropic damping forces in the horizontal and vertical direction. The whirling orbit of a flexible shaft is, in general, not a circular one but an ellipsoid, therefore, the whirling amplitude of the shaft at each rotating speed can be effectively minimized by controlling the damping forces independently. A pair of electrodes settled in the SFD to control the viscosity of lubricant was divided into a horizontal and vertical direction, and the directional controllability was investigated experimentally. Furthermore, and adaptive control system using an artificial neural network was constructed and its performance was studied.