自旋挠性航天器非约束模态动力学特性研究

Characterization of unconstrained modal dynamics of a spinning flexible spacecraft

在研究挠性航天器动力学问题时,关注的问题是挠性航天器系统的刚柔耦合作用问题,即航天器挠性附件的振动可能会造成航天器运动失稳。针对中心刚体-双侧大挠性结构的自旋航天器,提出了航天器帆板结构的梁式简化模型,建立了一种非约束模态动力学模型。本研究考虑受到万有引力作用,探讨自旋挠性航天器非约束模态的动力学建模及动态特性。首先利用欧拉方程和哈密顿原理建立了自旋挠性航天器动力学方程,方程解释了刚性模态和弹性模态之间的耦合;然后进行了模态离散化,分别在约束模态和非约束模态下对特征值问题开展研究,对频率和相关振型进行了定量比较;最后进行了数值仿真,求解了自旋挠性航天器非约束模态特征值问题,比较约束模态与非约束模态之间的差异,并用有限元进行验证,得到了随着梁长度的增加,即刚柔惯量比、质量比的减小,非约束模态比约束模态更加准确的结论。

In the study of dynamic problems of flexible spacecraft, the problem of rigid and flexible coupling of flexible spacecraft system is concerned, that is, the vibration of flexible appendage of spacecraft may cause instability of spacecraft motion.A beam simplified model of the spacecraft panel structure is proposed for a spinning flexible spacecraft with a central rigid body and bilateral large flexible structure and an unconstrained modal dynamics model is established.In this paper, the unconstrained modal dynamics modeling and characteristics of a spinning flexible spacecraft are discussed considering the action of universal gravitation.Firstly, the dynamic equation of the spinning flexible spacecraft is established by using Euler equation and Hamiltonian principle, which explains the coupling between rigid and elastic modes.Then the modal discretization is carried out, the eigenvalue problems of the constrained mode and unconstrained mode are discussed respectively, and the frequency and relevant modes of vibration are quantitatively compared.Finally, numerical simulation is carried out to solve the unconstrained mode eigenvalue problem of the spinning flexible spacecraft.The differences between the constrained mode and the unconstrained mode are compared and verified with the finite element method.The conclusion is that with the increase of the length of the beam, that is, with the decrease of the ratio of inertia and mass, the unconstrained mode is more accurate than the constrained mode.