柔性电动帆的轨道-姿态-挠性变形耦合机理及稳定控制研究

The novel idea of electric sail (electric solar wind sail) is an innovative propulsion concept, where the solar wind dynamic pressure is adopted to produce a thrust on a spaceship, such that reaction mass is negligible. The service life of electric sail is not affected by the limitation of fuel in the spaceship, and it is especially suitable for long-term space missions, such as deep space exploration and non-Kepler orbits. The study of the electric sail propulsion technology is just emerging, and the researches on the dynamics and control of electric sails are still focused on the rigid-body assumption models. The dynamics and control of flexible electric sail have become a key issue, which restrict the applications of the electric sail. In order to resolve this issue, this proposal would like to focus on the coupling mechanism of orbit-attitude-deformation and the stability control of flexible electric sails. An electric sail endures large deformations and large rotations during its motion, and the absolute nodal coordinate method is proposed here to study the coupling mechanism of orbit-attitude-deformation of the flexible electric sail. In consideration of the dynamical characteristics of the system, the terminal sliding mode control, input molding method and active disturbance rejection controller etc. is chosen for the control purpose, in order to achieve sufficient robustness of the dynamics of electric sails. The methodologies and conclusions of this study are expected to provide theoretical basis for the engineering application of electric sail and, then, provide theoretical method and key technology for the development of ultra long-distance deep-space exploration.

电动帆(全称为电动太阳风帆)是一种利用太阳风动能冲力飞行的新兴无质损推进方式，其运行寿命不受有限燃料的约束，因此特别适用于长期的空间飞行任务，如深空探测及非开普勒轨道保持等。由于电动帆推进技术刚刚兴起，目前电动帆动力学及控制方面的研究还停留在刚体假设模型上，柔性电动帆的动力学及控制已成为制约电动帆实际应用的关键问题。本申请针对以上问题，以柔性电动帆为研究对象，对其轨道-姿态-挠性变形动力学耦合机理问题及稳定控制问题开展研究。针对电动帆具有大变形和大转动特性，采用绝对节点坐标方法进行建模，研究太阳风环境场下电动帆轨道-姿态-挠性变形动力学耦合机理。针对电动帆的动力学特性，采用终端滑模控制、输入成型法和自抗扰控制等对电动帆进行控制，在保证电动帆挠性振动小的同时提高控制系统鲁棒性。此方面的研究成果可为电动帆的工程化应用提供理论指导，为我国超远距离深空探测的发展提供可借鉴的理论方法和关键技术。

本项目针对目前柔性电动帆动力学建模与控制方面存在的问题，综合考虑了电动帆大尺寸、大挠性结构、低刚度、弱阻尼、低频率等强非线性动力学特性以及太阳风粒子速度、密度、温度、入射角度和金属链电压的因素，开展了对柔性电动帆的轨道-姿态-挠性变形动力学耦合机理及稳定控制方法研究。基于绝对节点坐标法开展了单根柔性带电金属链动力学建模研究，并以此为基础建立了柔性电动帆整体轨道-姿态-挠性变形耦合动力学模型，再结合太阳风动压广义外力，通过数值模拟手段对柔性电动帆动力学耦合机理开展了研究。同时，以柔性电动帆耦合动力学模型为支撑，针对电动帆飞行力学及日心悬浮轨道特性，对电动帆航天器的轨道-姿态耦合稳定控制进行了研究，提出了一套适用于电动帆轨道-姿态-挠性变形耦合稳定控制的控制策略。通过本项目研究，揭示了柔性电动帆轨道-姿态-挠性变形间的动力学耦合机理，部分解决了柔性电动帆轨道-姿态-挠性变形耦合动力学与控制方面的问题，为推进电动帆的实际应用奠定了一定的理论基础，可以促进我国深空探测研究领域的发展，特别在发展无燃料损耗推进及新型的深空探测飞行器方面具有重要的科学意义和现实意义。