X射线脉冲星信号检测及位相测量技术研究
发布时间：2018-07-15 13:27
【摘要】：脉冲星导航概念自提出以来,已经经过了近半个世纪,但直到十多年前利用X射线脉冲星导航定位可行性得到论证后,才逐渐受到重视。得益于其独特的信号辐射方式以及脉冲周期的稳定性,X射线脉冲星已成为目前人们所认识的十分理想的天文导航信源,并在空间航天器自主导航领域表现出了良好的应用前景。目前,国际上已经开展了利用X射线脉冲星的自主导航技术的空间试验研究,但这项新型技术仍处在基础理论研究和可行性验证阶段。特别是在国内,有关脉冲星导航的实质性的研究才刚刚起步,诸如极弱X射线脉冲星信号高精度计时观测、高效高性能位相测量、时间传递误差修正等制约X射线脉冲星导航(XPNAV)精度提高的关键问题仍没有得到很好的解决。本文主要围绕XPNAV中的信号检测、累积轮廓建立和位相测量等问题展开研究,主要工作内容包括： (1)分析了可用于脉冲星信号检测的多个特征参量,如周期、轮廓和流量强度等。单独利用周期或轮廓频域特征检测和辨识脉冲星信号的方法可行,但对于强度极弱、探测技术较为复杂的X射线脉冲星信号,这些方法并不令人满意。已有研究表明,由于频域方法存在谐波和色噪声等因素的影响,在对X射线脉冲星信号的检测中存在失效的情况,而时域方法有时表现的更好。将累积轮廓、流量和周期三个重要特征应用于X射线脉冲星信号检测中,提出基于Bayesian估计的时域检测方法。利用仿真数据和(?)XTE卫星的实测数据进行实验验证显示,该法性能优于同类的基于高斯分布模型的检测方法,在检测信号的同时能在一定精度下给出信号位相偏移值。 (2)利用累积轮廓进行位相测量是XPNAV导航信息获取的基本途径,轮廓累积的重要性不言而喻。对转化到SSB原点处的X射线脉冲星光子序列,传统的轮廓累积方法是先识别信号周期,然后再按周期折叠累加得到脉冲轮廓。这种方法依赖于周期识别的准确性,对累积轮廓质量也无评价标准。本文分析了脉冲星累积轮廓和周期的强相关性,提出了周期未知时直接进行轮廓累积的最小熵方法,并对其进行证明,在此基础上,讨论了该方法在周期识别中的作用。利用仿真数据和RXTE卫星的实测数据实验验证了该方法的有效性。脉冲星累积轮廓通常被认为是脉冲星辐射区结构一维分布的反映,人们在对大量累积轮廓统计分析中发现这些轮廓均具有核成分,进而提出利用累积轮廓的高斯成分分离方法分析脉冲星辐射区结构。我们将高斯成分分离方法用于脉冲星累积轮廓建模,发现该模型可以很好地逼近标准轮廓,并将该模型用于累积轮廓位相测量的CRLB分析中,以评价累积轮廓成分对位相测量的影响。结果显示轮廓成分间的相关性和轮廓成分宽度是影响测相精度的两个重要因素。 (3)考虑到Taylor FFT等频域位相测量的实质是在投影定理下用各次谐波的线性叠加对原函数拟合,提出了基于最小熵准则的位相测量高斯拟合方法。实验说明,所提方法在相对较低信噪比条件下,性能优于Taylor FFT方法。鉴于该方法对轮廓质量要求较高,在实际应用中可能造成困难,本文建立了一种新的脉冲星信号概率模型,用于描述在观测时间内光子到达频度随采样时间的分布。分析表明该模型可以很好的刻画轮廓形变与周期误差间的关系。进而本文提出基于该模型的位相和位相速率联合测量方法,将多普勒效应视为参量,利用所提概率模型描述信号的直接累积轮廓,然后利用优化方法求解。仿真实验说明该方法对累积轮廓质量要求较低,能进行位相和位相速率联合测量,且位相测量精度优于Taylor FFT方法。 (4)从XPNAV的性能来看,其定位误差不到最小模糊距离的十分之一,因此连续正常工作时,可以不考虑整周期模糊问题。而对于初始位置未知或者因系统故障导致位置记忆丧失的情况,模糊问题是不可避免的。穷举搜索法是XPNAV常用且有效的解模糊方法,其不足之处在于复杂度高。本文提出一种快速空间搜索方法。该方法依据脉冲星的特征周期将搜索空间划分为多个子空间,利用相位投影增量建立基于满二叉树的快速搜索算法遍历子空间解模糊。仿真实验说明,得益于搜索空间约束和快速二叉树搜索,该方法能有效提高模糊空间搜索速率。 (5)尽管XPNAV相对于其它天文导航方法优势明显,但目前为止,它并不算一个成熟的导航方法。传统的天文自主导航方法利用地球等对星光掩蔽作用进行轨道航天器定轨,利用星敏感器观测恒星和地球问的角距等作为信息输入,与XPNAV机理完全不同。为提高导航精度,增强自主性,提出一种将脉冲星位相测量和星敏感器星光角距测量结合的信息融合天文自主导航方法,并基于UKF (Unscented Kalman Filter)使用真轨道参数做了仿真实验,结果表明组合两种导航方法能有效提高位置和速度估计精度。进而我们也对XPNAV与其它导航系统组合的可能性和有效性做了分析讨论。 (6)地面仿真系统研制在导航系统研究中具有重要意义,由于在地面上无法接收脉冲星的空间辐射X射线信号,对XPNAV而言地面仿真尤其重要。本文设计了一种X射线脉冲星导航信号仿真方案,重点讨论了虚拟参考系建立、信号建模以及硬件系统构成。
[Abstract]:Since the concept of pulsar navigation has been proposed for nearly half a century, it has been gradually paid more attention to the feasibility of using X ray pulsar navigation and positioning until more than 10 years ago. Thanks to its unique mode of signal radiation and the stability of the pulse cycle, the X ray pulsar has become a great reason that people have known at present. In the field of autonomous navigation of space spacecraft, space experiments have been carried out by X ray pulsar autonomous navigation technology, but the new technology is still in the stage of basic theoretical research and feasibility verification. The substantial research of star navigation has just started, such as the high precision time observation of the extremely weak X ray pulsar signal, high performance and high performance phase measurement, time transfer error correction and other key problems that restrict the improvement of the precision of the X ray pulsar navigation (XPNAV). This paper mainly focuses on the signal detection in the XPNAV. Research on contour establishment and phase measurement has been carried out.
(1) several characteristic parameters, such as cycle, contour and flow intensity, which can be used for pulsar signal detection, are analyzed. The method of detecting and identifying pulsar signals using the characteristics of periodic or contour frequency domain alone is feasible. However, these methods are not satisfactory for X ray pulse star signals with very weak intensity and more complex detection technology. It is shown that, due to the influence of harmonic and color noise in the frequency domain, the detection of the X ray pulsar signal is invalid, and the time domain method sometimes performs better. The three important features of the cumulative contour, flow and period are applied to the X ray pulsar signal detection, and the time domain detection based on the Bayesian estimation is proposed. Method. The simulation data and the measured data of (?) XTE satellite show that the performance of the method is better than that of the same kind of detection method based on Gauss distribution model, and the phase shift of signal can be given at a certain precision while the signal is detected.
(2) phase measurement using cumulative contour is the basic way for XPNAV navigation information acquisition. The importance of contour accumulation is self-evident. For the X ray pulsar photon sequence converted to the origin of SSB, the traditional method of contour accumulation is to identify the signal cycle first and then fold and accumulate the pulse contour according to the cycle. This method depends on the week. In this paper, we analyze the strong correlation between the accumulative contour and the period of the pulsars, and put forward the minimum entropy method for the direct contour accumulation when the period is unknown. On this basis, the function of the method in the periodic recognition is discussed. The simulation data and the RXTE are used. The experimental data test of the satellite shows the effectiveness of the method. The accumulative contour of pulsar is usually considered as a reflection of the one-dimensional distribution of the structure of the pulsar radiation area. People find that these outlines have nuclear components in the statistical analysis of a large number of cumulative outlines, and then the Gauss component separation method of cumulative contour is proposed to analyze pulsars. The structure of the radiation area. We use the Gauss component separation method to model the cumulative contour of pulsars. It is found that the model can be well approximated to the standard contour, and the model is used in the CRLB analysis of the cumulative profile phase measurement to evaluate the influence of the cumulative contour components on the phase measurement. The results show the correlation and contour between the contour components. The width is the two important factor affecting the accuracy of phase measurement.
(3) considering the essence of the phase measurement of Taylor FFT and other frequency domain phase measurements is to fit the original function with the linear superposition of every harmonic in the projection theorem, a phase measurement Gauss fitting method based on the minimum entropy criterion is proposed. The experiment shows that the proposed method is superior to the Taylor FFT method under the relatively low SNR condition. A new probability model of pulsar signal is established in this paper to describe the distribution of photon arrival frequency within the observation time. The analysis shows that the model can well describe the relationship between the contour deformation and the periodic error. The Doppler effect is considered as a parameter, and the proposed probability model is used to describe the direct cumulative contour of the signal, and then the optimization method is used to solve the problem. The simulation experiment shows that the method is low in the quality of the cumulative contour, and can be combined to measure the phase and phase velocity, and the phase measurement accuracy is better than Taylo. R FFT method.
(4) from the performance of XPNAV, the positioning error is less than 1/10 of the minimum fuzzy distance, so the fuzzy problem is unavoidable when the initial position is unknown or the position memory loss caused by the system failure. The exhaustive search method is commonly used and effective for the XPNAV. In this paper, a fast spatial search method is proposed. This method divides the search space into multiple subspaces based on the characteristic period of the pulsar, and builds a fast search algorithm based on the full two forked tree by the phase projection increment. Search space constraint and fast two binary tree search method can effectively improve the search speed of fuzzy space.
(5) although XPNAV has obvious advantages over other astronomical navigation methods, it is not a mature navigation method so far. The traditional astronomical autonomous navigation method uses the earth and so on to track the orbit of the orbital spacecraft, and uses the star sensor to observe the angle of the star and the earth as the information input, and the XPNAV machine. In order to improve the navigation accuracy and enhance the autonomy, an information fusion method for astronomical autonomous navigation is proposed, which combines the pulse star phase measurement with the star sensor star angle measurement, and based on the real orbit parameters of the UKF (Unscented Kalman Filter), the results show that the combined two navigation methods can be effectively improved. We also analyze and discuss the possibility and effectiveness of combining XPNAV with other navigation systems.
(6) the development of the ground simulation system is of great significance in the study of the navigation system. Because of the inability to receive the space radiated X ray signals of the pulsar on the ground, the ground simulation is especially important for the XPNAV. This paper designs a simulation scheme of the X ray pulsar navigation signal, focusing on the establishment of the virtual reference system, the signal modeling and the hard work. Component system composition.
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：P145.6
[Abstract]:Since the concept of pulsar navigation has been proposed for nearly half a century, it has been gradually paid more attention to the feasibility of using X ray pulsar navigation and positioning until more than 10 years ago. Thanks to its unique mode of signal radiation and the stability of the pulse cycle, the X ray pulsar has become a great reason that people have known at present. In the field of autonomous navigation of space spacecraft, space experiments have been carried out by X ray pulsar autonomous navigation technology, but the new technology is still in the stage of basic theoretical research and feasibility verification. The substantial research of star navigation has just started, such as the high precision time observation of the extremely weak X ray pulsar signal, high performance and high performance phase measurement, time transfer error correction and other key problems that restrict the improvement of the precision of the X ray pulsar navigation (XPNAV). This paper mainly focuses on the signal detection in the XPNAV. Research on contour establishment and phase measurement has been carried out.
(1) several characteristic parameters, such as cycle, contour and flow intensity, which can be used for pulsar signal detection, are analyzed. The method of detecting and identifying pulsar signals using the characteristics of periodic or contour frequency domain alone is feasible. However, these methods are not satisfactory for X ray pulse star signals with very weak intensity and more complex detection technology. It is shown that, due to the influence of harmonic and color noise in the frequency domain, the detection of the X ray pulsar signal is invalid, and the time domain method sometimes performs better. The three important features of the cumulative contour, flow and period are applied to the X ray pulsar signal detection, and the time domain detection based on the Bayesian estimation is proposed. Method. The simulation data and the measured data of (?) XTE satellite show that the performance of the method is better than that of the same kind of detection method based on Gauss distribution model, and the phase shift of signal can be given at a certain precision while the signal is detected.
(2) phase measurement using cumulative contour is the basic way for XPNAV navigation information acquisition. The importance of contour accumulation is self-evident. For the X ray pulsar photon sequence converted to the origin of SSB, the traditional method of contour accumulation is to identify the signal cycle first and then fold and accumulate the pulse contour according to the cycle. This method depends on the week. In this paper, we analyze the strong correlation between the accumulative contour and the period of the pulsars, and put forward the minimum entropy method for the direct contour accumulation when the period is unknown. On this basis, the function of the method in the periodic recognition is discussed. The simulation data and the RXTE are used. The experimental data test of the satellite shows the effectiveness of the method. The accumulative contour of pulsar is usually considered as a reflection of the one-dimensional distribution of the structure of the pulsar radiation area. People find that these outlines have nuclear components in the statistical analysis of a large number of cumulative outlines, and then the Gauss component separation method of cumulative contour is proposed to analyze pulsars. The structure of the radiation area. We use the Gauss component separation method to model the cumulative contour of pulsars. It is found that the model can be well approximated to the standard contour, and the model is used in the CRLB analysis of the cumulative profile phase measurement to evaluate the influence of the cumulative contour components on the phase measurement. The results show the correlation and contour between the contour components. The width is the two important factor affecting the accuracy of phase measurement.
(3) considering the essence of the phase measurement of Taylor FFT and other frequency domain phase measurements is to fit the original function with the linear superposition of every harmonic in the projection theorem, a phase measurement Gauss fitting method based on the minimum entropy criterion is proposed. The experiment shows that the proposed method is superior to the Taylor FFT method under the relatively low SNR condition. A new probability model of pulsar signal is established in this paper to describe the distribution of photon arrival frequency within the observation time. The analysis shows that the model can well describe the relationship between the contour deformation and the periodic error. The Doppler effect is considered as a parameter, and the proposed probability model is used to describe the direct cumulative contour of the signal, and then the optimization method is used to solve the problem. The simulation experiment shows that the method is low in the quality of the cumulative contour, and can be combined to measure the phase and phase velocity, and the phase measurement accuracy is better than Taylo. R FFT method.
(4) from the performance of XPNAV, the positioning error is less than 1/10 of the minimum fuzzy distance, so the fuzzy problem is unavoidable when the initial position is unknown or the position memory loss caused by the system failure. The exhaustive search method is commonly used and effective for the XPNAV. In this paper, a fast spatial search method is proposed. This method divides the search space into multiple subspaces based on the characteristic period of the pulsar, and builds a fast search algorithm based on the full two forked tree by the phase projection increment. Search space constraint and fast two binary tree search method can effectively improve the search speed of fuzzy space.
(5) although XPNAV has obvious advantages over other astronomical navigation methods, it is not a mature navigation method so far. The traditional astronomical autonomous navigation method uses the earth and so on to track the orbit of the orbital spacecraft, and uses the star sensor to observe the angle of the star and the earth as the information input, and the XPNAV machine. In order to improve the navigation accuracy and enhance the autonomy, an information fusion method for astronomical autonomous navigation is proposed, which combines the pulse star phase measurement with the star sensor star angle measurement, and based on the real orbit parameters of the UKF (Unscented Kalman Filter), the results show that the combined two navigation methods can be effectively improved. We also analyze and discuss the possibility and effectiveness of combining XPNAV with other navigation systems.
(6) the development of the ground simulation system is of great significance in the study of the navigation system. Because of the inability to receive the space radiated X ray signals of the pulsar on the ground, the ground simulation is especially important for the XPNAV. This paper designs a simulation scheme of the X ray pulsar navigation signal, focusing on the establishment of the virtual reference system, the signal modeling and the hard work. Component system composition.
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：P145.6
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