挠性航天器太阳翼全局模态动力学建模与实验研究

STUDY ON GLOBAL MODE DYNAMIC MODELING AND EXPERIMENT FOR A SOLAR ARRAY OF THE FLEXIBLE SPACECRAFT

现代柔性航天器通常安装有大型太阳翼为其在轨运行提供所需动力.航天器入轨后太阳翼展开并锁定成为铰链连接多板结构,此类结构质量轻、跨度大、刚度低的特点使其低频振动和非线性振动问题越来越凸显.分析和处理此类结构出现的复杂振动问题的关键在于建立系统精确的非线性动力学模型.为此,本文提出铰链连接多板结构解析全局模态的提取方法,获取太阳翼的固有频率和解析函数表征的全局模态.提出可变刚度的扭转弹簧等效模型,考虑铰链非线性刚度及摩擦力矩等因素,通过全局模态离散得到系统的低维高精度非线性动力学模型,研究了太阳翼在周期激励作用下的非线性特性.开展太阳翼地面振动实验研究,采用锤击法获取系统模态,利用振动台施加正弦扫频激励,将物理实验结果与理论结果进行对比,从而验证全局模态动力学建模方法的合理性与准确性.结果表明,铰链刚度等结构参数对系统固有特性的影响较大,铰链的存在会使太阳翼的动态响应出现跳跃等非线性现象.全局模态动力学建模方法能很好地解决多板结构在非经典边界下解析全局模态求解的困难,系统全局模态反映的是系统各个部件弹性振动的真实模态,所建立的动力学模型具有低维高精度的特点,对于复杂组合结构非线性动力学建模具有重要的参考价值.

Modern flexible spacecraft are usually installed with large solar arrays to provide the power needed for the operation of the spacecraft in orbit. The solar arrays are expanded in orbit and locked into hinged multi-panel structures,and the characteristics such as light weight, large span, and low stiffness make the issues on the study of low frequency and nonlinear vibration become more and more important. The key process of dealing with the vibration for such a kind of structure is to establish the exact nonlinear dynamic model of the system. In this paper, an analytic extraction method of the global mode of the multi-panel structure is presented, and the natural frequencies and the global analytic mode functions of the solar array are obtained. Considering the nonlinear stiffness and friction moments of the hinges, and the nonlinear dynamic model of the system can be obtained by the global mode discretization. The nonlinear characteristics of the solar array under periodic excitation are studied. The experimental researches on the solar array are carried out, and the mode shapes are obtained by hammering tests, and the sinusoidal sweep excitation is applied by the vibration table.The physical experimental results are compared with the theoretical results, so as to verify the rationality and accuracy of the global mode dynamic modeling method. The experimental results show that the structural parameters such as hinge stiffness have a great influence on the inherent characteristics of the system, and the existence of hinges will make the dynamic response of the solar array appear nonlinear phenomena such as jump. Global mode dynamical modeling method can well solve the difficult problem of obtaining the analytical global mode for the multi-panel structure with the non-classical boundaries. The global mode of the system can reflect the real elastic vibration mode of the parts in the system, and the established dynamic model is low-dimensional and high-precision. It has important reference value for nonlinear dynamic modeling of complex composite structures.