并联式承载减振一体的整星隔振研究

RESEARCH ON WHOLE-SPACECRAFT VIBRATION ISOLATION BASED ON PARALLEL LOAD-BEARING AND DAMPING SYSTEM

整星隔振是一种改善卫星振动环境的有效措施,传统整星隔振方案主要通过在卫星与火箭之间插入柔性、高阻尼结构.该方案因串联柔性元件,在实现减振的同时,也导致卫星分支(卫星、卫星支架、过渡支架)及整个运载火箭的模态频率大幅降低和卫星振动位移的显著增大.前者严重影响运载火箭飞行特别是末级飞行的稳定性;后者则会大幅减小卫星与整流罩的动态间隙,严重时可能导致卫星与整流罩碰撞.为了解决串联式整星隔振存在的问题,本文提出了一种在原主承力(过渡支架)结构中并联阻尼元件的整星隔振方案,该方案不改变卫星分支结构形式、连接关系,不影响卫星分支主承力结构的强度和刚度.根据柔性航天器的特点,建立了多自由度系统动力学模型,通过仿真分析研究了不同阻尼特性对系统共振频率附近传递特性的影响,得到了增大阻尼可有效改善系统各阶共振频率附近的振动传递特性.根据某运载火箭的外激励特点、过渡支架结构形式、卫星减振需求,设计的一种黏性阻尼器及其安装支架,通过在过渡支架均匀分布8个减振单元,构建了并联式承载减振一体的整星隔振方案,有限元分析和试验结果表明,该方案与无减振状态相比,卫星分支频率变化小于±5%,共振频率处传递特性改善30%～40%.

Whole-satellite vibration isolation is an effective measure to improve the satellite vibration environment. Traditional Whole-Satellite vibration isolation schemes mainly insert flexible and high-damping structures between satellite and rocket. Due to the series of flexible components, the scheme achieves vibration reduction, and also causes a significant decrease in the modal frequencies of satellite branches(satellite, satellite brackets, transition brackets) and the entire launch vehicle with a remarkably increase in satellite vibration displacement. The former seriously affects the flight stability of launch vehicle, especially the stability of final stage, while the latter greatly reduces the dynamic clearance between satellite and fairing, which may lead to collision between satellite and fairing in severe cases. In order to solve the problem of series whole-satellite vibration isolation, this paper presents a whole-satellite vibration isolation scheme with parallel dampers in the original main bearing structure(transition support). This scheme does not change the form and connection relationship of satellite branch structure, and does not affect the strength and stiffness of satellite branch main bearing structure. According to the characteristics of flexible spacecraft, a multi-degree-of-freedom system dynamics model is established. The effects of different damping characteristics on the transmission characteristics near the resonance frequencies of the system are analyzed by simulation. It is concluded that increasing damping can effectively improve the vibration transmission characteristics near the resonance frequencies of the system. A viscous damper and its mounting bracket are designed according to the external excitation characteristics of a launch vehicle, the structural form of transition support and vibration reduction requirement of satellite. By evenly distributing eight vibration reduction units in the transition support, a whole satellite vibration isolation scheme with Parallel bearing and vibration reduction is constructed. Finite element analysis and experimental results show that the variation of satellite branch frequencies is less than 5%and the transmission characteristics at resonance frequencies are improved by 30%~40%compared with the non-vibration state.