Highly reliable relative navigation for multi-UAV formation flight in urban environments

Formation flight of multiple Unmanned Aerial Vehicles (UAVs) is expected to bring significant benefits to a wide range of applications. Accurate and reliable relative position information is a prerequisite to safely maintain a fairly close distance between UAVs and to achieve inner-system collision avoidance. However, Global Navigation Satellite System (GNSS) measurements are vulnerable to erroneous signals in urban canyons, which could potentially lead to catastrophic consequences. Accordingly, on the basis of performing relative positioning with double differenced pseudoranges, this paper develops an integrity monitoring framework to improve navigation integrity (a measure of reliability) in urban environments. On the one hand, this framework includes a fault detection and exclusion scheme to protect against measurement faults. To accommodate urban scenarios, spatial dependence in the faults are taken into consideration by this scheme. On the other hand, relative protection level is rigorously derived to describe the probabilistic error bound of the navigation output. This indicator can be used to evaluate collision risk and to warn collision danger in real time. The proposed algorithms are validated by both simulations and flight experiments. Simulation results quantitatively reveal the sensitivity of navigation performance to receiver configurations and environmental conditions. And experimental results suggest high efficiency and effectiveness of the new integrity monitoring framework.     

一种基于相干叠加的复合载波导航信号捕获方法

针对复合载波导航信号多载波结构特征,基于检测性能、运算复杂度、硬件资源占用情况三方面的综合考虑,提出了一套适用于该信号的捕获架构和处理方法。该架构采用PMF-FFT算法对复合载波各子载波进行分别或统一处理,然后利用各子载波频点间隔信息,对信号进行循环移位并相干叠加,以充分利用信号能量进行检测判决。理论分析和仿真实验表明,与传统的卫星导航信号单载波捕获架构相比,该架构在有限的硬件资源和计算能力的情况下获得了较好的检测性能。     

导航卫星高精度太阳光压摄动分析建模及验证

为提高导航卫星精密定轨与轨道预报精度,提出了一种导航卫星太阳光压摄动的分析建模方法.相较于其他摄动因素模型完善且精度较高,光压摄动由于太阳活动导致太阳能量误差、卫星姿态控制误差和表面材料老化等问题,是最难以精确建模的摄动源,也是动力学模型最大的误差源.基于此,提出了一种基于卫星的姿态控制规律,通过分析法建立卫星太阳光压摄动模型,给出了光压摄动加速度在星体坐标系中的模型,并以GPSBlock IIR为例进行了验证.计算结果表明,该仿真分析法所建立的摄动模型与T30模型、ECOM模型精度接近,达到了光压建模研究的初步计算要求.     

X射线脉冲星自主导航的光子到达时间转换

根据广义相对论的后牛顿近似时空理论, 在忽略太阳系天体自转和扁率的情况下, 详细推导出X射线脉冲星自主导航中, 光子到达观测航天器和太阳系质心的时间差值, 它是对现行公式的修正．导出了质心坐标时与航天器固有时的变换关系, 根据这一关系, 建议在脉冲星导航的工程设计中可以仿照GPS, 将航天器携带时钟作频率调整, 从而有利于工程计算.      

移动工业机器人在飞机装配生产线中的应用研究

在总结移动工业机器人在飞机装配生产线等航空制造场景典型应用的基础上,重点分析了移动工业机器人多传感器融合的同步定位和建图、移动机器人导航控制、机械臂精度控制和数字化测量等关键技术,并对未来航空领域移动机器人的人机协作、多传感器数据融合、智能规划与决策、数字孪生体系等发展趋势进行了阐述。     

一种利用地球敏感器的星光导航方法

针对直接敏感地平的红外地平仪-星光导航系统精度低的问题,提出通过建立扁率误差补偿函数,研究扁率引起的姿态角测量误差;建立地心矢量的姿态角误差模型,通过修正地球扁率误差来补偿姿态角,对卫星施加姿态偏转指令调整地心矢量偏移。同时基于SODERN地球红外辐射模型,考虑红外辐射强度随纬度和季节的变化建立真实红外辐射曲线,通过滤波算法获得精确的地球切线边缘的量测信息,提高红外地平仪测量精度。仿真结果表明,该方法有效提高了基于红外地平仪的星光导航定位方法的可靠性和精度,导航位置误差能达到500m左右,较原有系统提高3倍以上。     

Feasibility study of autonomous orbit determination using only the crosslink range measurement for a combined navigation constellation

In order to expand the coverage area of satellite navigation systems, a combined navigation constellation which is formed by a global navigation constellation and a Lagrangian navigation constellation was studied. Only the crosslink range measurement was used to achieve long-term precise autonomous orbit determination for the combined navigation constellation, and the measurement model was derived. Simulations of 180 days based on the international global navigation satellite system(GNSS) service(IGS) ephemeris showed that the mentioned autonomous orbit determination method worked well in the Earth–Moon system. Statistical results were used to analyze the accuracy of autonomous orbit determination under the influences of different Lagrangian satellite constellations.     

嫦娥三号巡视器的惯导与视觉组合定姿定位

针对“嫦娥三号”的“玉兔号”巡视器在月面未知环境中避障与安全行进的要求,分析和阐述了“玉兔号”巡视器在地面遥操作中心的控制下利用惯导和视觉组合进行月面导航与精确定位的实现方法,并结合现有的导航定位研究对“玉兔号”巡视器导航与定位的工程创新性进行了总结,阐明了惯导定位和视觉定位技术在“玉兔号”巡视器月面探测过程中的工程应用特点.最后,通过“玉兔号”巡视器着月点的精确定位实验,验证惯导和视觉相结合的定位方法的有效性,定位精度近似达到总行驶里程的1％,这对“玉兔号”巡视器开展月面探索和准确抵达科学目标位置具有重要作用.     

Analytical long-term evolution and perturbation compensation models for BeiDou MEO satellites

The current paper establishes the analytical models of the long-term evolution and perturbation compensation strategy for Medium Earth Orbits(MEO)shallow-resonant navigation constellation,with application to the Chinese Bei Dou Navigation Satellite System(BDS).The long-term perturbation model for the relative motion is developed based on the Hamiltonian model,and the long-term evolution law is analyzed.The relationship between the control boundary of the constellation and the offset of the orbital elements is analyzed,and a general analytical method for calculating the offset of the orbit elements is proposed.The analytical model is further improved when the luni-solar perturbations are included.The long-term evolutions of the BDS MEO constellation within 10 years are illustrated,and the effectiveness of the proposed analytical perturbation compensation calculation approach is compared with the traditional numerical results.We found the fundamental reason for the nonlinear variations of the relative longitude of ascending node and the mean argument of latitude is the long-periodic variations of the orbital inclination due to the luni-solar perturbations.The proposed analytical approach can avoid the numerical iterations,and reveal the essential relationship between the orbital element offsets and the secular drifts of the constellation configuration.Moreover,there is no need for maintaining the BDS MEO constellation within 10 years while using the perturbation compensation method.     

北斗卫星导航系统空间信号用户测距误差计算方法研究

按照空间信号用户测距误差（UserRangeError,URE）定义,参考GPS标准定位服务性能规范中URE的计算方法,结合北斗卫星导航系统（BDS）多星混合星座类型,在考虑仰角限制情况下,详细推导了适用于BDS的瞬时URE和均方根URE计算公式。利用广播星历和精密星历计算的卫星轨道误差和卫星钟钟差,带入所推导的公式,对BDSURE进行分析评估;并使用GNSS接收机原始观测量和伪距观测方程计算BDSURE,最后将两种计算结果进行对比分析。研究结果表明,两种方法BDSURE的计算结果基本一致,在95%置信度情况下均小于2.5m,满足北斗公开服务性能规范中对空间信号URE的基本要求。