电动帆航天器姿态动力学与控制研究

An electric sail is an innovative propulsion concept that uses the ambient solar wind momentum for spacecraft thrust. The momentum exchange between the electric sail and the solar wind is achieved by establishing a huge positive electric filed around the spacecraft, and repelling the particles with positive charge, thus the thrust is extracted from the solar wind. The major component of an electric sail is a number (on the order of 100) of long conducting main tethers. They are connected to a solar-powered election gun for which the aim is to maintain the tethers at a high (up to 20kV) positive potential. On the tips of the main tethers, auxiliary terms are attached for the attitude control. The whole system is spinning around an axis to deploy and stretch the tethers. It can be viewed as a typical multibody system. The electric sail has infinite specific impulse and an ultralow mass. It is rather suitable for interstellar flight. There have been many studies about the orbit design of the electric sail, but few studies focus on its attitude dynamics and control issue, which involves many difficult theoretical and technical problems: the tethers of the electric sail are prone to have large deformation and coupled with the solar wind through Coulomb forces; the deployment of the sail is rather complicated; the spin rate and the spin direction of the electric sail are also coupled; the number of the actuators (the auxiliary tethers) for the attitude control is enormous, which makes the steering law design difficult. To settle the above problems, this study will focus on: dynamic modeling of a single tether with high positive potential in the solar wind; the detailed dynamics of the deployment of the electric sail; the equivalent simplified model of the system; design the control law for the system spin motion; designing the steering law of the controllable potential on the tethers for the attitude control. This study will complete the theory of the electric sail, and provide the foundations for the practical applications of the electric sail, moreover, the developed theories and methods will further enrich the theories of dynamics and control of multibody systems.

电动帆是一种新兴的不消耗工质的推进方式，其通过建立巨大的正电势电场改变太阳风中正电荷粒子的运动方向，从而与太阳风发生动量交换，获得推力。电动帆的主要组件是约100根15~20km长的绕中心体均匀分布的高电势导线，导线端部带有辅助导线用于姿态控制，整个系统通过自旋维持展开，属于典型的大尺度柔性多体系统。电动帆能够实现低成本的航天任务，目前已有众多基于电动帆的轨道设计；但是鲜见系统姿态动力学和控制研究，该问题涉及到多个理论和技术难点：电动帆导线易发生大范围变形、与太阳风通过库仑力耦合，系统释放展开过程复杂，自旋速率与自旋面方向存在耦合，导线数量众多且作用机理复杂。针对以上问题，本项目将分别研究：单根高电势导线在太阳风环境中的动力学建模；电动帆展开过程精细建模与分析；电动帆等效简化模型；分别设计系统自旋控制律，导线电势操纵律。本研究将完善现有电动帆理论，也将丰富多体系统动力学和控制领域的成果。

电动帆是一种新兴的不消耗工质的推进方式，其通过建立巨大的正电势电场改变太阳风中正电荷粒子的运动方向，从而与太阳风发生动量交换，获得推力。电动帆的主要组件是约100根15~20km长的绕中心体均匀分布的高电势导线，导线端部带有辅助导线用于姿态控制，属于典型的大尺度柔性多体系统。本项目针对该系统的姿态动力学与控制问题所涉及到的多个理论和技术难点，开展了深入的研究，主要研究内容与进展如下：.建立了多种电动帆导线运动模型与电动帆整体姿态动力学模型，并对导线运动和电动帆姿态运动模式进行分析。研究表明：电动帆自旋速率处于规定的上下界间时导线形变为慢变量，且导线形变造成的其两端的相对运动可分解为自旋面面内的运动及面外摆动分别考虑；当帆面垂直于太阳风时帆面面外摆动周期与自旋角速率成反比、摆动幅值与自旋角速率的平方成反比。.研究了基于辅助执行机构的电动帆姿态控制问题，验证了采用辅助绳系对主导线和电动帆构型实现被动控制的可行性，设计了电动帆的姿态控制律、执行机构配置方案和操纵律。研究表明：通过导线末端小推力器与主导线电势变化结合，以及导线末端小推力器与小型太阳帆结合，这两种执行机构配置方案可以实现电动帆姿态跟踪控制即自旋面指向及自旋速率控制。.综上，本项目研究了电动帆这类复杂多体航天器的姿态运动机理、验证了通过辅助执行机构对电动帆姿态进行控制的可能，完善了电动帆理论体系，为这一新兴无工质推进方式的实际应用提供理论基础。在本项目的支持下，共计发表SCI期刊论文8篇，国际学术会议论文4篇，国内学术会议论文1篇；培养硕士生1人，博士生1人。