【作者】 何玲；

【导师】 郑钢铁；

【作者基本信息】 哈尔滨工业大学 ， 一般力学与力学基础， 2007， 博士

【摘要】 整星隔振技术是利用隔振器改造或替代原有星箭适配器,有效改善卫星在发射过程中的动力学环境的一种方法。这里,星箭适配器(也称卫星支架)是连接卫星和运载火箭的部段。其中以流体阻尼器为阻尼元件搭建多作动器隔振平台是实现整星隔振技术的一种重要方式。与其它阻尼形式相比,流体阻尼具有工作变形小,但可提供较大作动力的特点,并且其隔振系统的阻尼和刚度可以相互独立。为了给流体阻尼器及隔振平台的设计及应用提供参考依据,本文以流体阻尼器为研究对象,结合其在多作动器隔振平台中的应用,对影响流体阻尼器隔振特性的非线性因素进行了深入的理论分析和实验研究。本文首先通过研究流体阻尼的形成机制,建立流体阻尼力的函数表达式。并结合整星隔振平台对作动器的要求,设计了几种不同结构形式的流体阻尼隔振器,对它们进行相应的理论分析和实验验证。针对实验验证时活塞式流体阻尼器在不同激励幅值条件下出现明显不同的隔振特性的现象,提出用双线性滞后模型描述阻尼器中存在的摩擦力,建立单个阻尼器的非线性动力学方程,并利用谐波平衡法分析摩擦力对隔振性能的影响。然后分别在采用两参数作动器模型和三参数作动器模型的基础上考虑单个作动器上的摩擦力作用,建立隔振平台的非线性动力学模型并进行分析。结果表明,无论单个隔振器,还是隔振平台,由于摩擦力作用,均存在粘着和滑动两种状态,当激励幅值较小时,摩擦力表现为刚度,使系统共振频率提高,隔振带宽减小。对波纹管式流体阻尼器进行实验验证,结果发现阻尼器具有两自由度系统的特征。因此提出考虑流体附加质量的作用,并计入流体的二次非线性阻尼,建立阻尼器的两自由度模型,较好的解释了实验现象。由此建立相应的八作动器隔振平台的动力学模型,并讨论流体质量和非线性阻尼对隔振性能的影响。结果表明,当阻尼值较小时,流体质量的作用不可忽视,阻尼器在高频段会出现明显的共振,从而降低隔振效果;当阻尼较大时,流体质量作用可以被忽略,系统可简化为单自由度三参数模型。流体阻尼的主要特征是能量转换和能量耗散。根据流体的粘温特性,考虑流体温度与阻尼力之间的相互作用,在动力学方程的基础上附加流体阻尼器的热平衡方程,建立流体阻尼器的热动力学模型。并采用短时傅立叶变换对该时变非线性系统进行时频分析,讨论粘性发热对隔振性能的影响。结果发现,随着时间推移,系统温度升高,阻尼降低,隔振特性发生改变,共振频率及共振峰值发生变化,直到系统达到动平衡状态。在实际工况中,多种非线性因素相互耦合,同时发生作用,因此最后分析了同时考虑流体粘性发热和摩擦力作用的隔振器模型,结果发现当存在摩擦力时,粘性发热作用的影响可以忽略。对波纹管式流体阻尼器,在两自由度模型基础上同时考虑粘性发热作用,建立热动力学模型。结果发现,当阻尼值较小时,粘性发热作用影响可忽略;但是当阻尼较大时,粘性发热对隔振性能存在影响,其趋势与单自由度三参数模型相同。更多还原

【Abstract】 Compared to other damping, the fluid damping provides a higher load capacity with a smaller displacement. And the stiffness and damping coefficient of the isolator are completely independent. The idea of Whole-Spacecraft Vibration Isolation (WSVI) is to put an isolator into or use it to replace a payload attach fitting, which is a section connecting the launch vehicle and the spacecraft, and can effectively improve the dynamic environment of the satellite. The Multi-Actuator Vibration Isolation Platform (MVIP), in which the fluid damper is selected as actuator, is an important method of WSVI. To provide the references to the design of the fluid damper and platform, in this dissertation, based on the fluid damper and its application in MVIP, the nonlinear elements which affect the characteristics of the fluid damper are investigated both theoretically and experimentally.With the research of the mechanism of fluid damping, the expression of the fluid damping force is established. And to meet the requirement on the actuator of MVIP, some types of the fluid damper is designed, analyzed and tested.During the experiment of fluid damper with a piston, we found that the performance of damper is different with different excitation amplitude. Based on the bi-linear hysteresis model which is used to describe the friction force in the damper, the nonlinear dynamic equation of the damper is established and solved by the harmonic balance method. And the effect of the friction on the performance of the damper is investigated. Moreover, considering the effect of the friction, the nonlinear dynamic models of an MVIP with eight actuators (OVIP) are established with two kinds of the passive actuator: the two-parameter model and the three-parameter model. The results show that no matter what in single damper, or OVIP, the friction interface has two states: sticking and slipping. Under the small excitation amplitude, the friction force behaves as spring and causes a shift of resonant frequency.From the experiment of the fluid damper with bellows, it is found that the characteristic of the damper behaves as a two degree-of-freedom system. So a two degree-of-freedom model, which accounts for the mass and the nonlinear damping of the fluid, is established. Furthermore, the dynamic equation of the OVIP which is composed of this type of damper is developed. And the effect of the fluid mass and the nonlinear damping on the performance of the isolator is discussed. The results indicate that when the damping is small, the effect of the fluid mass must be taken into account, which will cause a resonance in high frequencies and thus reduce the performance of vibration isolation. If the damping is large enough, the effect of the fluid mass can be negligible and the model of damper can be simplified as the three-parameter model.The energy transformation and heat exchange are the major characteristics of a fluid damping. Based on the temperature-viscosity characteristics of the fluid, the interaction effect of the fluid damping force and the fluid temperature is studied. And the thermodynamic equation of the damper, which includes a heat balance equation, is established. The Short Time Fourier Transform is applied to analyze the dynamic performance in the time and frequency domain for dealing with the time variance and the nonlinearity of the system induced by the effect of viscous heating. It is found that with the past of the time, the temperature of the damper increased, and thus resulted in a shift of the resonance frequency and the changes of the resonance amplitude, until the system reaches a dynamic balance.In the actual condition, many nonlinear factors operate simultaneously and couple with each other. So the combining effect of viscous heating and friction force in the damper with a piston is investigated. And it is concluded from the numerical results that when the friction force is taken into account, the effect of the viscous heating on the performance of vibration isolation can be negligible. In consideration of the effect of the viscous heating, the thermodynamic model of the damper with bellows is developed based on the two degrees-of-freedom system. Analysis shows that with a small damping coefficient, the effect of the viscous heating can be neglected. But in the condition of a large damping coefficient, the effect of viscous heating must be taken into account. In addition, the property of system is same as the condition of the single degree-of-freedom.更多还原