【作者】 杜宁；

【导师】 崔祜涛；

【作者基本信息】 哈尔滨工业大学 ， 飞行器设计， 2008， 硕士

【摘要】 小天体撞击探测任务具有很大的科学意义和价值。在撞击器接近目标天体过程中,自主导航精度与撞击制导律的选取将直接决定撞击探测任务的成功与否以及最终的撞击性能。本课题进行了高精度小天体撞击探测自主导航与制导方法研究。首先,为避免星历误差的影响,采用对目标天体的直接观测方案,建立了简化的相对轨道动力学模型和以目标天体图像信息为观测量的观测模型。根据小天体撞击任务的特殊条件,采用B平面参数描述撞击器导航系统的方法,避免了撞击器与目标天体径向距离不可观测带来的问题。在对导航系统可观测性分析的基础上,设计了基于扩展卡尔曼滤波的自主导航算法。其次,在自主导航基础上,基于预测制导思想,进行了小天体撞击探测的精确制导律设计。引入动力学模型预测末端状态,通过优化机动脉冲使预测与期望的撞击点偏差最小。结合任务周期设计了时刻固定的三次点火机动方案,并给出了小推力发动机点火控制的修正方法。最后,设计了小天体撞击探测导航制导数学仿真平台,对影响导航与制导系统精度的各误差源进行分析,并建立了其数学模型,在此基础上进行蒙特卡罗仿真。仿真结果验证了所提出的导航制导方法是可行的,撞击精度达到了148.8m。更多还原

【Abstract】 The deep impact mission has great scientific values and implications. The autonomous navigation accuracies and the guidance laws of the impactor during the approach phase are key elements for the impact mission. This dissertation studied a high precision autonomous navigation and guidance strategy for small body impact missions.Firstly, in order to overcome ephemeris uncertainty effects, a reduced orbit dynamics model and an observation model using the target image information as navigation measurement are constructed. Considering the special conditions of small body impact missions, the B-plane reference frame is imported to solve unobservable problems of a radial position between an impactor and the target. Afterwards, basing on the observability analysis of the navigation system, an autonomous navigation method based on extended Kalman filtering is presented in this paper.Secondly, a predictive guidance and control law is presented based on the autonomous navigation system proposed. The algorithm uses dynamic model to predict the terminal states, and minimize maneuver computation errors by optimizing the impulsive maneuvers. The paper also presents a conceptual design of the impactor targeting maneuver method which consists of three discrete magnitude burns for small-body-impact missions, and describes the fine trajectory correction methods in the case of low thrust engineFinally, a mathematical simulation platform for the guidance and navigation system for small body impact missions is built. Monte Carlo simulations are provided to validate the feasibility of the algorithms, and effects of the major errors sources on navigation and guidance accuracies are presented. The simulation results show that the guidance and navigation methods presented in this paper are effective with final impact site error is about 148.8m.更多还原