The Study on Semi-Active Damper

本研究的目的是研究电流控制的半主动阻尼器。阻尼器的工作液采用粘性系数随磁流体变化的磁流体。阻尼器的卸料比例可以在没有机械系统的情况下改变。本研究由三个阶段组成：(1)基础实验--研究磁性液体用作减振器时的基本特性。(2)汽车悬架半主动减振器样机的制作。(3)理论研究--研究半主动悬架系统的控制。在基础实验中，测量了磁极形状、间隙距离、线圈中的电流和活塞速度变化时流体速度与压差的关系。倾倒系数随水流的变化而变化。这种变化是由粘度的变化引起的。它的比例随着流体速度(雷诺数)的减小而增加。在设计和制造半主动阻尼器的原型时，利用这种机构的上述特性是很重要的。设计并制作了阻尼器样机。产生倾卸力的部分放置在气缸的外部。这种形式的优点是降低了流体的速度，避免了电磁的热效应。在理论研究中，重点研究了它在车辆悬架中的应用。最优控制理论不仅适用于半主动悬架，也适用于主动悬架。

The purpose of this research is to investigate semi-active dampers which are controlled by electric current. Magnetic fluid whose viscous coefficient varies according to the magnetic fluid is used for working fluid of the dampers. Dumping ration of the dampers can be changed without mechanical system. This research is composed of three phases:(1) Fundamental experiments -- to investigate basic properties of magnetic fluid when it is used for dampers.(2) Making prototypes of semi-active dampers for automobile suspensions.(3) Theoretical study -- to investigate how to control the semiactive suspension system.In the Fundamental experiments relations between fluid velocity and pressure difference are measured under the variety of shape of magnetic poles, gap distance, current in coil and piston velocity. Dumping coefficient changes according to current. The change is caused by changes of viscosity. Its ratio increases as the velocity of the fluid (Reynolds number) decreases.In design and making prototypes of semi-active dampers it is important to use the above feature of this mechanism. Prototype dampers are designed and made. The part which yields dumping force are placed outside of the cylinder. The advantages of this form is to reduce the fluid velocity and to avoid heat effects from electric magnet.In theoretical study the application to vehicle suspensions is focused. Optimal control theory is applied to not only semi-active suspensions but also active suspension.