【作者】 兰盛昌；

【导师】 徐国栋；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2011， 博士

【摘要】 新世纪的太空资源争夺日趋激烈,世界各国开展了针对未来空间的应用研究,其间脉冲星导航作为传统导航技术的挑战者和有益补充,成为今后研究和探讨的焦点。采用脉冲星信号作为导航信息的来源,能够避免近地导航系统作用范围小的缺点,又完全独立,不受使用权限的限制,同时还能提供时间、姿态、位置等多方面的导航信息。对脉冲星的导航前景进行分析,同时对关键性技术进行攻关和突破,有利于在激烈的竞争中占据主导地位。本文结合“十一五”预研背景项目和国家高技术研究发展计划(863)项目,对脉冲星信号处理进行深入研究,重点解决导航信号的获取、识别问题以及基于脉冲星观测的姿态测量问题、航天器间相对距离测量问题,具体工作如下:首先在分析课题的目的和意义,广泛地总结和分析现有导航系统的发展概况的基础上,通过与现有的导航系统进行对比,结合航天器编队飞行的特点,详细地阐述并分析了脉冲星信号获取、识别及其在空间应用等方面的研究现状。其次针对脉冲星的信号特性讨论了脉冲星的基本分类,对现有的脉冲星辐射机制、信号特性以及谱特性进行分析;对脉冲星特性进行研究,为后续脉冲星信号的识别以及测量奠定理论基础。针对脉冲星信号的获取技术,提出采用多谱段时频相干接收的方法,通过扩大探测器对脉冲星光子的频率响应范围,降低对单一时间相干累积的依赖,同时利用EMD分解等多种手段用于对脉冲星信号进行去噪声处理,采用近似熵作为EMD信号复原所需测量的后向叠加算法判断阈值,并且在此基础上,提出无阈值的塔式EMD分解的噪声处理方法。其后针对脉冲星的信号特点,提出了以脉冲星的瞬时频率和瞬时幅度作为不同脉冲星辨识的特征,并采用能量中心频率以及奇异值特征优化降维处理方法对数据进行压缩,再利用BP神经网络算法等方法对脉冲星信号进行自适应识别。第三章的研究方法涉及非平稳信号处理、神经网络以及模式识别方法等。针对基于X射线脉冲星的姿态测量问题,提出了一种基于X射线脉冲星平行光线多平面观测的姿态测量方法,该方法引入了平行光线观测的设计方法,通过测量不同平面内接收的X射线脉冲星光子能量,以及测量值和各平面之间的相对几何关系,计算出脉冲星矢量的幅值和空间角,从而实现了脉冲星矢量的测量。通过对多颗脉冲星的观测,可以获得多个脉冲星矢量,利用多个矢量能够完成姿态的测量。最后研究利用脉冲星观测确定航天器编队间相对距离确定的方法,针对脉冲星信号的特性以及编队卫星系统的特点,采用相关处理的方法实现编队航天器系统中相对距离的估计,并对相对距离测量观测所需的脉冲星类型及其频谱特性进行分析,同时针对脉冲星信号的周期特性以及目前星间相对距离估计方法的局限性提出了基于信号子空间旋转实现编队航天器系统中相对距离估计的方法,利用多个脉冲星敏感器的接收数据估计星间相对距离,同时结合脉冲星信号的特征,分析估计的精度,并且利用了实际脉冲星的观测数据进行了数学仿真,仿真结果表明基于子空间旋转的星间相对距离估计能够有效的提高测量的精度。更多还原

【Abstract】 The competition of space resource in new epoch has undertaken among the countries worldwide and pulsar navigation as the effective substitute and challenge to the traditional counterpart becomes the focus of the research and exploration. Pulsar signal as the source of navigation information is beneficial in the navigation range and on the other hand independent from the usage license limitation. Meanwhile it supplies synchronization, vehicle attitude and position information for spacecraft navigation. Analysis towards pulsar navigation perspectives and key technology breakthrough leads to a predominant position in competition. This thesis combined with the eleventh five years project background and national high technology research development project explores the pulsar processing technology for its application in the navigation of formation flying spacecraft, mainly focus on pulsar signal denoising, identification, and attitude measurement as well as relative ranging based on pulsar navigation, the details as follows.First of all, on the basis of current research statement, this thesis summarizes the research method and development of pulsars navigation for distributed satellite system, and then by analyzing the research method, this paper indicates the research direction of pulsars navigation for distributed satellite system in future researches.Secondly the thesis discusses the pulsar classification according to the signal characeristic and the analysis covers the pulsar emission signals and spectrum characteristic which is the theoretical foundation of the pulsar identification and measurements.Then considering the extraction of pulsar signals, the thesis presents a method of pulsar signal denoising based on empirical mode docomposition. Meawhile entropy is selected as the threshold to decide the operation of postfitting of the signal. Furthermore, a tower-like multiple EMD is derived later.Considering the pulsar signal’s characteristic it is proposed that the identification of pulsars is implemented via instantaneous amplitude and frequency extracted via Hilbert-huang Transformation; Then BP neural network algorithm are respectively applied to identify the different pulsarsMoreover, this paper describes the design, tests and preliminary results of a multiple-plane sensor detecting the X-ray pulsars vectors to acquire the spacecraft attitude. Comparing to the star sensors or other traditional attitude measuring, the multiple-plane sensor has made an adversary and new effort by inventing a multiple-plane structure, with the orthogonal vectors pointing towards the different directions. By measuring the power received by each plane and considering the geometry relationship of the planes, the sensor computes the pulsars vector from a certain pulsar. Therefore, the attitude of the spacecraft can be acquired if vectors from several different pulsars is recognized and specified. Accordingly the simulation is established and the result proves its charming feasibility in future spacecraft missions.Finally, a novel method of intersatellite ranging calibration is presented based on the observation of pulsars. According to the method intersatellite range projected in the direction of pulsars can be directly determined by correlating the pulsar signals detected on different spacecrafts in a distributed satellite system. Meanwhile accuracy of the method is derived based on the analysis of the celestial sources and their spectras. The method is evaluated using the realistic simulation of the pulsars and orbit information of distributes spacecraft. The result verifies the feasibility of in the application of the future distributed satellite system. Then according to the method intersatellite range projected in the direction of pulsars can be directly determined by using the rotational invariance of the pulsar signals detected on different spacecrafts in a distributed satellite system. Meanwhile accuracy of the method is derived based on the analysis of the celestial sources and their spectrums. The method is evaluated using the realistic simulation of the pulsars and orbit information of distributed spacecraft. The result verifies the feasibility of in the application of the future distributed satellite system.更多还原