Directionally Controllable Squeeze Film Damper Using Liquid Crystal

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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.