磁流变液挤压流动机理及磁流变挤压阀式减振器特性研究

It is noted that increasing the fuel economy and decreasing the price of the automobiles would deteriorate other performances including the NVH (Noise, Vibration and Harshness) and the comfort. In order to improve the ride comfort, the handling and the total quality of an automobile, last few years have witnessed the increasing interests in the development of the semi-active suspension since it is easy to make a compromise between the handling, ride comfort, and additional energy consumption. However, few semi-active dampers are now commercially available in automobiles. The problem is mainly caused by the unsolved technical issues such as the manufacturing of the throttle and the slow response of the actuator. On the other hand, the smart materials and the advanced control theory have been drawn lots of attention. We are trying to apply the state-of-art technology in the smart materials and the advanced control theory to solve the existing problems and promote the industrialization of the semi-active suspension. Magneto-rheological fluids are smart materials that respond to an applied magnetic field in terms of a change in rheological behavior. Typically, this change is manifested by the development of a yield stress which monotonically increases with the applied field. Research has shown that magneto-rheological fluids have large force capabilities in the squeeze mode. Hence, a magneto-rheological squeeze valve will be proposed and studied in this proposal based on the behaviors of magneto-rheological fluids in squeeze mode. With the purpose of making a trade-off between the handling and the ride comfort, the magneto-rheological squeeze valve will be assembled in a passive damper for its online damping control. In short, the research presented in this proposal focuses on the behaviors of magneto-rheological fluids squeeze flow and characteristics of an automotive damper with magneto-rheological squeeze valve, including the following key points: (1) the research on the behaviors of magneto-rheological fluids squeeze flow with inertia and wall slip, (2) its effect on the characteristics of an automotive damper, (3) optimal design of the magneto-rheological squeeze valve and its' magnetic field supplied system, (4) the research on the behaviors of the magneto-rheological squeeze valve damper and its application on a semi-active suspension. Three major contributions are expected in this research. The first is studying and modeling of magneto-rheological fluids squeeze flow characteristics with inertia and wall slip, which is the foundation for the further application of the magneto-rheological squeeze flow. Secondly, a novel automotive damper with magneto-rheological squeeze valve will be proposed and fabricated. The third is modeling and verification of the characteristics of this novel damper, which will be used by a semi-active suspension to improve the handling, the ride comfort and the total quality of an automobile.

现代汽车正朝着安全、舒适、节能、环保、智能化的方向发展，人们对汽车的舒适性和整体品质的追求日益提升。半主动悬架能很好兼顾舒适性、操纵稳定性，且能量需求小，是当前关注的热点。但是，常见的节流阀加工难、响应慢，制约了其推广应用。本项目拟采用理论与试验相结合的方法，研究磁流变液挤压流动特性的机理和基于磁流变液挤压阀的汽车减振器特性，并将其应用于汽车半主动悬架，以期提高汽车的舒适性和整体品质。重点研究：（1）考虑惯性力、边界滑移的磁流变液挤压流动的机理；（2）磁流变挤压阀对减振器特性的影响规律；（3）磁流变挤压阀及磁场供应系统的优化设计；（4）磁流变挤压阀式汽车减振器特性的研究及仿真应用。本研究的科学意义在于揭示考虑惯性和滑移的磁流变液挤压流动特性的规律，为其实际应用提供必要的理论基础；探明磁流变挤压阀对减振器阻尼特性影响机理，揭示该新型减振器阻尼特性的规律，为半主动悬架的设计和分析提供理论依据。

汽车的低碳化和智能化对悬架性能提出更高要求。半主动悬架能协调控制车身与轮胎的运动，且能量需求小，其高效能的执行器设计是当前研究热点。本项目发明了磁流变压力流量阀，重点研究了磁流变液挤压流动动力学机理及特性、磁流变压力流量阀和磁流变阀控减振器的优化设计方法、自适应半主动悬架控制策略。取得的主要成果和意义为：1)开发了活塞式和囊式磁流变液挤压流动动力学特性试验装置，探索了高频激励（达150Hz）和温度对磁流变液挤压流动动力学特性的影响规律，为理论研究提供支撑，试验结果表明高频激励下流体自身惯量的影响明显，且需要注意磁流变液响应速度的影响，发现常温下的挤压力最小，低温下挤压力变大的主要原因是磁流变液载体粘度的增加，高温下载体的粘度下降，在小间隙的挤压流动时可能出现铁微粒沉降，有利于挤压面内铁微粒的聚集，导致挤压力的增加，这还需要进一步探究；2)求解了考虑惯性力和 Navier边界滑移的磁流变液挤压流动的屈服表面，拓展了磁流变液挤压流动动力学特性的理论模型，揭示了考虑惯性力、屈服和边界滑移的磁流变液挤压流动机理，为其应用提供了理论基础，研究表明在设计基于挤压流动的磁流变装置时，应将活塞杆半径取为活塞头半径的1/7，能兼顾装置结构强度和性能要求；3)发明了高效能磁流变压力流量阀，其1A电流下的最大进出口压差可达10.86Mpa，在6L/min流量、0.0-1.0A电流下的压差可调倍数为6.78，为减振器阻尼调节及液压回路的压力控制提供一种切实可行的方案，提出等饱和强度磁场特性优化设计准则，建立磁流变压力流量阀的动力学模型，明确阀口流动机理，开发、测试并评价了磁流变压力流量阀动力学特性，为其应用提供理论依据和试验支撑；4)建立了磁流变阀控减振器的设计方法，实现其物理样机的开发和试验评价，该样机在速度0.52m/s时，拉伸行程阻尼力范围为2167-5213N，阻尼力增加了141%；压缩行程阻尼力范围为1105-1929N，阻尼力增加了75%；5)应用Baumgarte算法减少动力学系统速度和加速度相关项积分导致的迭代误差，提高求解精度，建立了左右相关的四轮随机路面的高频补偿方法，完善了四轮随机路面的表达，设计了考虑时变车速的汽车侧向稳定性控制的峰值能量增益调节的鲁棒控制器，完成了载荷自适应天棚控制策略典型工况试验验证，为半主动悬架汽车瞬态动力学特性及协调控制研究奠定基础。