【作者】 龚胜平；

【导师】 李俊峰；

【作者基本信息】 清华大学 ， 力学， 2009， 博士

【摘要】 深空探测贯穿人类发展史,在科学、技术、政治和文化方面都有重要意义。随着深空探测任务距地球越来越远,燃料成为限制深空探测发展的一个重要因素。于是,人们提出了多种新型的推进方式,其中太阳帆可以提供连续小推力且比冲无限大,被认为是最实际的方法之一。NASA和ESA有多项相关飞行任务正在研制之中。太阳帆航天器的动力学与控制问题是理论研究的重点,对飞行任务的实现具有重要意义。太阳帆航天器不同于传统航天器,轨道和姿态是强耦合的。本文给出了耦合系统在周期轨道上稳定的条件;在轨道不影响姿态的情况下,推导了耦合系统的稳定性与轨道稳定性、姿态稳定性的关系。在只考虑轨道动力学的情况下,分析了太阳帆的被动控制。被动控制要求太阳帆的法线方向与太阳光之间的夹角保持不变,此时太阳帆的轨道总是稳定的且其轨道参数由太阳帆的初始角动量唯一确定。根据被动分析结果和耦合系统稳定的条件,设计了能在日心悬浮轨道和人工拉格朗日点被动稳定飞行的太阳帆结构。太阳帆技术在未来很长时间内无法达到多个任务提出的太阳帆尺寸要求。本文提出了太阳帆航天器编队飞行的概念,研究了几种简单姿态控制律下,各种悬浮轨道附近相对运动的稳定性。定义了一套描述椭圆相对轨道的相对轨道根数,分析了简单控制律下稳定相对轨道的特征,结果表明相对轨道的形状和空间指向都受到限制。为了得到更丰富的相对轨道,同时考虑到相对速度测量困难,研究了仅利用位置反馈进行相对轨道设计的方法。并利用数值算例验证了该设计方法的有效性。拉格朗日点附近编队研究中很重要的一个领域为编队控制。研究结果表明:利用脉冲控制很难实现高精度编队,太阳帆能提供微牛以下的连续小推力可以满足小尺度高精度编队需求。由于太阳光压力的方向受到限制,并非所有编队控制都能利用太阳帆。本文给出了太阳帆控制能力范围内的直线编队和圆形编队,利用数值算例验证了太阳帆实现编队控制的可行性。在小行星牵引任务中,引力拖车方法的优点是不依赖小行星特性、可靠性高,缺点是偏移能力有限。本文将太阳帆控制在小行星附近的悬浮轨道,实现对小行星轨道的偏移;进一步利用引力拖车编队提高偏移能力,研究了悬浮轨道上引力拖车编队的控制策略。最后,比较了普通引力拖车和太阳帆引力拖车的偏移能力。更多还原

【Abstract】 Deep space exploration throughout the history of human being is very important in science, technology, politics and culture. Fuel becomes a bottleneck of the development of deep space explorations as the missions are far from the earth. Many new types of propulsion are proposed, where solar sail that can provide low thrust with infinite impulse is considered to be one of the most practical methods. There are several missions related to solar sail being studied by NASA and ESA. The dynamics and control of sailcraft is the key point of theoretical research, which is also very important for the achievement of solar sail missions.Different from traditional spacecraft, the orbit and attitude of solar sail are coupled strongly. Firstly, this thesis gives the conditions of solar sail being stable on periodic orbits and investigates the dependence of the coupled system stability on the orbit and attitude stability when only the attitude influences the orbit. Then, the passive control of solar sail is analyzed with only orbit dynamics considered. Passive control requires the angle between the normal vector of solar sail and the solar light direction to be constant. With passive control, the solar sail orbit is stable and its initial momentum determines the orbit parameters. Based on the conclusions of passive control and stable conditions of the coupled system, the passive stability configurations of solar sail on displaced solar orbit and at artificial Lagrange point are designed.Solar sail technology will not meet the solar sail size requirements in a long time. This thesis proposes the concept of solar sail formation flying and investigates the stability of relative motion near displaced orbits with several attitude control laws. A set of relative orbit elements are defined to describe the elliptic relative orbits. The shape and normal of the relative orbit are restricted to certain ranges. With the difficulty of measuring relative velocity considered, a relative orbit design method is proposed to obtain diverse relative orbits with only position feedback. Numerical simulations are employed to validate the design method.Formation control is one of the important research fields in formation flying around Lagrange point. The research results show that the impulse control can not achieve high-precision formation and the solar sail that can provide low thrust of micro-newton is able to achieve small-size high-precision formation. However, solar sail cannot realize all formation control because the direction of the solar sail radiation pressure force is restricted to certain range. This thesis gives the linear and circular formations that require the control forces within the capability of solar sail and numerical simulations are employed to test the validation of the solar sail control.The merits of gravitational tractor in asteroid deflections are its high reliability and independence of asteroid characteristics, and the demerit is its low deflection efficiency. In this thesis, the asteroid deflection is realized by controlling the gravitational tractor on a displaced orbit above the asteroid. The gravitational tractor formation flying is proposed to enhance the deflection ability and two formation control strategies are investigated. Lastly, the deflection capabilities of traditional gravitational tractor and solar sail gravitational tractor are compared.更多还原