基于零微重力地面仿真的零刚度系统动力学理论、实验与应用研究

Ground-level simulation for space zero- or micro-gravity environments plays an important role in the development space technology. The conventional technique to escape gravity acceleration by falling tower and parabolic flight is of expensive cost and the limit of time. Due to the non-zero stiffness supporting, the offset gravity methods of suspension and gas flotation exists the insufficient of lower precision and complex structures. Even there exist various kind of structures in practice with zero-stiffness (without ability to resist the elastic deformations), these systems have not been successfully used in ground-level zero- or micro-gravity simulations due to the lack of investigations to the theory dynamics theoretically, which results in the mechanism unclear and the lack of experimental methods leading to the obstacle to the applications in ground-level simulation. Here in this project we formulate the zero-stiffness dynamics based upon the series of nonlinear system with quasi-zero stiffness generated from the geometry nonlinearity of SD oscillators by constructing the dynamic models with zero-stiffness, investigating the degeneration of the double-zero eigenvalue property of the system and understanding the zero-stiffness dynamics and the response mechanism under the complex excitations. We carry out the experimental investigations to zero-stiffness systems by setting up the hovering devices with zero-stiffness to nullify the gravity within the pre-designed limit. We examine the devices in both the zero-stiffness dynamics and the hovering performance of zero- or micro-gravity to develop the technologies for zero-stiffness experiment. This project aims to explorer new route to the applications of ground-level zero-stiffness simulations for spacecraft and to solve the key problems of ground-level modal test for large-scale soft structures with the infulence from boundary constrains.

空间零微重力环境地面仿真是空间技术发展必不可少的重要环节。传统的释放重力加速度方法如落塔、飞机抛物线飞行等具有成本高、实验时间短的局限；基于非零刚度支撑的重力补偿系统如悬吊、气浮等存在着结构复杂、实验精度低的技术难题。尽管工程中存在着某些不具备抵抗弹性变形能力的零刚度系统，但由于零刚度动力学理论研究甚少，其响应机理不清、实验方法不完善，因而制约了零刚度系统在地面仿真领域的应用。本项目基于SD振子衍生的一系列非线性准零刚度系统建立零刚度系统动力学模型，研究零刚度系统双零特征根高次退化特性，厘清其复杂动力学行为及动力学响应机理，充实零刚度动力学理论体系；研制在一定预设范围内抵消物体重力的零刚度悬浮装置，进行其零刚度动力学特性与零微重力悬浮性能的测试，完善零刚度系统的实验方法；探讨零刚度系统应用于航天器空间零微重力环境地面仿真的新方法，解决空间柔性结构模态地面测试中边界约束干扰等工程应用难题。

本项目针对亟待解决的空间零微重力环境地面仿真难题，基于自2006年提出并建立的具有负刚度特征的SD振子族，建立了以高阶负刚度单元、多参数高余维分岔为主要特征的几何非线性动力学理论；结合传统支撑系统建立了具有高静低动特征的含有多个几何参数的高阶准零刚度隔振系统族，形成了完整的几何非线性隔振理论；最终提出了具有无穷余维、处处平衡的零刚度机械悬浮(Mechanical Suspensor)系统，该零刚度悬浮系统的提出使天地一致性地面动力学实验的开展(零微重力地面仿真)成为可能。同时该系统具有对环境振动中低频段、超低频段在内的全频段隔振能力，解决了Euler自1750年提出的长期困扰工程界的受迫系统的共振(Resonance)难题。项目组研制了多台零刚度机械悬浮装置，并开展了系列动力学测试工作，实验结果表明系统具有误差不超过9.016×10-4g的机械悬浮能力，同时验证了包括低频段、超低频段在内的全频段振动免疫能力。项目组同时开展了包括空间结构地面动力学仿真、移动******超稳平台及星箭隔振等一系列有关国防工业的应用研究，与既有线路高速重载铁路货车、超高压输电设备多自由度抗震以及城市地铁环境净化等重大民用工程中的动力学问题的相关研究与探讨，均取得了优异的研究成果。本项目以崭新的研究思路，发展具有零刚度特征的零微重力系统理论及实验技术方法，解决了航天器零微重力环境地面仿真试验精度和航空领域大型柔性结构模态试验中约束边界干扰等难题，为我国空间计划和尖端科学问题提供理论和技术支持。