Radio/FADS/IMU integrated navigation for Mars entry

Supposing future orbiting and landing collaborative exploration mission as the potential project background, this paper addresses the issue of Mars entry integrated navigation using radio beacon, flush air data sensing system (FADS), and inertial measurement unit (IMU). The range and Doppler information sensed from an orbiting radio beacon, the dynamic pressure and heating data sensed from flush air data sensing system, and acceleration and attitude angular rate outputs from an inertial measurement unit are integrated in an unscented Kalman filter to perform state estimation and suppress the system and measurement noise. Computer simulations show that the proposed integrated navigation scheme can enhance the navigation accuracy, which enables precise entry guidance for the given Mars orbiting and landing collaborative exploration mission.     

MCAV/IMU integrated navigation for the powered descent phase of Mars EDL

Pin-point landing is considered as a key technology for future manned Mars landing and Mars base missions. The traditional inertial navigation system (INS) based guidance, navigation and control (GNC) mode used in the Mars entry, descent and landing (EDL) phase has no ability to achieve the precise and safe Mars landing, so novel EDL GNC methodologies should be investigated to meet this goal. This paper proposes the MCAV/IMU integrated navigation scheme for the powered descent phase of Mars EDL. The Miniature Coherent Altimeter and Velocimeter (MCAV) is adopted to correct the inertial bias and drift and improve the performance of integrated navigation. Altitude and velocity information derived from MCAV and the lander’s state information sensed by inertial measurement unit (IMU) are integrated in extended Kalman filter algorithm. The validity of the proposed navigation scheme is confirmed by computer simulation.     

火星精确定点着陆多信息融合自主导航与控制方法研究

针对火星定点采样、载人登陆和基地构建等任务的需求,提出了一种火星精确定点着陆多信息融合自主导航与控制(Guidance Navigation and Control,GNC)方案。针对大气进入前的高精度导航需求,提出了基于X射线脉冲星和火星表面陆标图像的融合自主导航方法;针对火星着陆探测进入、下降和着陆(Entry,Descent and Landing,EDL)过程的高精度绝对和相对导航需求,提出了基于陆标图像、IMU(Inertial Measurement Unit)和测距测速信息的多信息融合自主导航方法;针对精确定点着陆要求,设计了大气进入和动力下降过程的制导与控制算法。数学仿真结果表明,提出的方案能够实现高精度的定点着陆(精度100 m)和相对避障(精度为0.5 m),可满足任务需求。     

An innovative navigation scheme of powered descent phase for Mars pinpoint landing

Pinpoint landing (within 100 m from the target) is essential for future Mars exploration missions. This paper deals with one aspect of the pinpoint landing architecture—the navigation performance improvement during the powered descent phase, and proposes an innovative navigation scheme to obtain the vehicle complete and accurate states. On the basis of dead reckoning relying on the Inertial Measurement Unit, measurements of the Integrated Doppler Radar are adopted to correct the vehicle velocity and altitude. Distance between the vehicle and one Mars Orbiter as well as their line-of-sight relative velocity is measured by a radio sensor, and integrated in the filter to correct the vehicle horizontal position. The innovative navigation system is based on an Extend Kalman Filter. Two observation schemes are developed. One considers measurements of the Integrated Doppler Radar and radio range measurement. Another further considers radio velocity measurement. The performance of the innovative navigation scheme is greatly influenced by the position of the Mars Orbiter with respect to the target. Stochastic analyses are performed to obtain optimal locations of Mars Orbiter. Finally, the innovative navigation scheme performances are assessed through stochastic simulations. Its performance improvements are demonstrated by comparison with the Integrated Doppler Radar only navigation scheme.     

Deep reinforcement learning for six degree-of-freedom planetary landing

This work develops a deep reinforcement learning based approach for Six Degree-of-Freedom (DOF) planetary powered descent and landing. Future Mars missions will require advanced guidance, navigation, and control algorithms for the powered descent phase to target specific surface locations and achieve pinpoint accuracy (landing error ellipse <5 m radius). This requires both a navigation system capable of estimating the lander’s state in real-time and a guidance and control system that can map the estimated lander state to a commanded thrust for each lander engine. In this paper, we present a novel integrated guidance and control algorithm designed by applying the principles of reinforcement learning theory. The latter is used to learn a policy mapping the lander’s estimated state directly to a commanded thrust for each engine, resulting in accurate and almost fuel-optimal trajectories over a realistic deployment ellipse. Specifically, we use proximal policy optimization, a policy gradient method, to learn the policy. Another contribution of this paper is the use of different discount rates for terminal and shaping rewards, which significantly enhances optimization performance. We present simulation results demonstrating the guidance and control system’s performance in a 6-DOF simulation environment and demonstrate robustness to noise and system parameter uncertainty.     

太阳电池电路深空探测服役环境与关键技术分析

针对月球、火星、木星等不同的深空探测任务，本文通过在轨服役环境分析，说明了火星探测火星表面光谱计算方法、火星光谱太阳电池设计思路、火星表面除尘技术路线及木星探测低温低光强技术风险。结合工程技术经验，给出了特殊任务应用条件下单片太阳电池推算整板输出功率的计算方法，解决了我国尚无特殊条件的瞬态大太阳模拟器作为整板输出功率测试地面模拟光源的工程难题，为相关科研人员提供参考。     

基于IMU/FADS/无线电的火星上升器组合导航方案

以火星采样返回任务中火星表面上升为背景，研究了基于惯性测量单元（Inertial Measurement Unit, IMU）、嵌入式大气数据传感系统（Flush Air Data Sensing System, FADS）和无线电信标的组合导航方法。首先，在传统的IMU导航框架中加入由无线电测量获得的相对距离、速度信息，以及由FADS获取的动压、温度数据，建立了基于IMU、无线电和FADS的导航观测模型；然后，基于无迹卡尔曼滤波（Unscented Kalman Filter, UKF）技术对测量信息进行了融合，并压制了过程噪声和测量噪声，从而对上升器的状态进行了联合估计；最后，在数值仿真中，将UKF与自适应无迹卡尔曼滤波（Adaptive Unscented Kalman Filter, AUKF）技术进行了对比，在比较不同滤波器性能的同时，验证了组合导航方法的有效性。     

月球软着陆过程高精度自主导航避障方法

针对未知地形和障碍会危及着陆安全的问题,给出了一种月球软着陆过程高精度自主导航避障方法,主要包括基于IMU配以测距测速修正的自主绝对导航、障碍识别与目标着陆点选取、针对目标着陆点的相对导航与相对避障控制等算法。该方法在保证着陆精度的同时也大大降低了着陆过程遇到障碍的风险,提高了系统的安全性,已成功应用于实际工程任务。     

On the observability of Mars entry navigation using radiometric measurements

A thorough observability analysis of the Mars entry navigation using radiometric measurements from ground based beacons is performed. This analysis involves the evaluation of the Fisher information matrix which is derived from the maximum likelihood estimation. A series of navigation cases with multiple beacons are investigated, and both range and range-rate measurements are considered. The determinant of Fisher information matrix is used to quantify the observability of navigation system, while the trace of Fisher information matrix is used to determine the lower-bound of estimation errors. For one and two beacon cases, the navigation system is unobservable. However, the eigenvectors of Fisher information matrix give the observable and unobservable component. When three or more beacon measurements are employed, the states of entry vehicle become observable. Some valuable analytic conclusions on the relationship between the geometric configuration of beacons and observability are obtained consequently. Finally, simulation results from two navigation examples indicate that our effort is useful for understanding and assessing the observability of the Mars entry navigation using radiometric measurements.     

月球软着陆的高精度自主导航与控制方法研究

提出了一种月球软着陆的高精度自主导航和控制方法.根据测距波束视线相对月面的几何关系,确定本体系的月心方向,组合利用测速仪获取的本体系三维速度确定本体系相对轨道系的姿态、速度及高度,并根据确定的参数性质选取适应的制导和控制方法.算法基于直接测量数据确定和控制姿态、高度和速度,不受惯性导航误差的影响,可以有效地提高姿态、速度与高度的确定精度和控制精度.数学仿真表明了算法的有效性.     

捷联惯导/里程计组合导航方法

针对车载自主导航需求,基于卡尔曼滤波器,实现捷联惯导与里程计量测信息的组合导航.推导了里程计误差模型,结合捷联惯组误差模型与捷联系统误差模型,建立了捷联惯导/里程计自主组合导航系统误差状态模型.建立了捷联惯导/里程计组合导航量测模型,阐述了估计误差修正方法.采用仿真计算对此方法进行了验证,仿真结果表明:组合导航过程中,初始姿态误差能得到有效估计,姿态误差和位置误差均能控制在一定精度范围内,应用此组合导航方法相对于传统的航位推算方法能得到更高的导航精度,能有效实现自主高精度定位定向.     

China's Lunar and Deep Space Exploration Program for the Next Decade (2020-2030)

China has carried out four unmanned missions to the Moon since it launched Chang'E-1, the first lunar orbiter in 2007. With the implementation of the Chang'E-5 mission this year, the three phases of the lunar exploration program, namely orbiting, landing and returning, have been completed. In the plan of follow-up unmanned lunar exploration missions, it is planned to establish an experimental lunar research station at the lunar south pole by 2030 through the implementation of several missions, laying a foundation for the establishment of practical lunar research station in the future. China successfully launched its first Mars probe on 23 July 2020, followed in future by an asteroid mission, second Mars mission, and a mission to explore Jupiter and its moons.      

Optical/radio/pulsars integrated navigation for Mars orbiter

In this paper, we address the issue of the integrated navigation algorithm with different combination of measurements for Mars orbiter. First, system dynamic model and navigation measurement models using optical measurement information, radio measurement information and X-ray pulsars measurement information are respectively established. Second, optical/radio/pulsars integrated navigation algorithm is proposed, and observability analysis of the integrated navigation system is also conducted. Third, adaptive extended Kalman filter is adopted to fuse measurement information and suppress measurement and process noise to optimally estimate the state of Mars orbiter. Monte Carlo simulation results show that optical/radio/pulsars integrated navigation can effectively improve the navigation accuracy and satisfy the navigation requirements of Mars orbiter.     

伪卫星/惯性组合导航的非线性补偿

伪卫星具有抗干扰能力强和布置灵活机动的特点,在增强卫星系统和独立组网为用户提供更高精度导航定位信息方面具有广阔的应用前景.研究了一种伪卫星/惯性组合导航的非线性补偿算法.由于伪卫星与用户的距离比卫星近得多,其非线性量测的影响也严重得多.采用二次项修正一定程度上弥补了传统线性化方法存在的模型误差大、滤波效果差甚至发散的问题.为避免求解非线性方程的困难使用了两步估计方法,大大降低了算法的复杂度.仿真结果表明,该算法可以显著提高伪卫星/惯性组合导航系统的性能,具有很高的实用性.     

火星大气进入下降着陆段测控通信关键技术研究

着眼于我国首次火星探测任务着陆器EDL(Entry Descent and Landing)飞行段高风险特性,结合火星大气和地表环境分析了这一飞行阶段的主要特点和难点,系统地回顾了国外历次火星着陆任务的基本概况和任务失败的经验教训,并以美国"好奇号"着陆任务为例介绍了EDL期间可采用的主要通信手段,详细梳理了火星大气黑障段通信策略、调制体制选择以及高动态弱信号检测处理方案等测控通信需要解决的关键技术。最后对我国首次火星探测任务的关键技术攻关,任务准备和实施提出了建议。     

基于空中对准过程的在线标定及优化设计

光纤陀螺惯组输出误差影响武器系统导航精度,为了弥补地面标定的不足,利用机载制导武器发射前空中对准过程进行光纤捷联系统在线标定.介绍了光纤捷联系统空中对准/在线标定系统模型,基于此设计卡尔曼滤波器;针对某机载航空制导炸弹工作过程进行了对准过程中误差激发与对导航精度影响的仿真分析,并基于此进行了滤波器优化设计;最后进行了优化设计前后导航精度仿真比较,仿真结果显示:完成空中对准/在线标定优化设计后,光纤捷联系统纯惯性导航精度得到提高.      

Active disturbance rejection control for drag tracking in mars entry guidance

Future Mars missions will require precision landing capability, which motivates the need for entry closed-loop guidance schemes. A new tracking law – active disturbance rejection control (ADRC) – is presented in this paper. The ability of the ADRC tracking law to handle the atmospheric models and the vehicle’s aerodynamic errors is investigated. Monte Carlo simulations with dispersions in entry state variables, drag and lift coefficients, and atmospheric density show effectiveness of the proposed algorithm.     

火星探测接近段的光学自主导航研究

目前光学自主导航技术已成为深空探测计划中的重点研究对象. 已有研究, 多侧重于光学自主导航技术在深空探测巡航段或是对小行星探测接近段中的应用, 而关于大行星探测接近段光学自主导航技术的研究比较少. 结合中国即将开展的火星探测计划, 研究了探测器在火星探测接近段中利用火星进行光学自主导航的整个过程, 提出了适用于接近段的动力学模型、光学观测模型及自主导航滤波算法. 通过对自主导航系统的可观测性分析, 证明了仅利用火星光学信息进行自主导航的可行性. 仿真计算结果表明, 在接近段, 整个光学自主导航的持续时间约为40h. 在自主导航的最后5h内, 滤波结果稳定, 探测器的总体位置误差在40km以内, 速度误差在0.25m·s-1以内. 计算结果的精度满足实际任务需求, 对中国火星探测计划具有直接的参考价值.      

基于视觉的无人作战飞机自主着陆导航方案

提出了基于视觉的无人作战飞机自主着陆组合导航方案.基于视觉的自主着陆 组合导航系统,可以根据视觉、惯导、高度表等传感器系统的特点,融合各机载传感器的测 量信息,在不依赖外部导航信息的情况下,得到无人作战飞机(UCAV)相对于跑道的着陆导 航信息.由于视觉信息在导航系统中的重要作用,对计算机视觉算法及其实时性进行了讨论 .对如何将视觉信息与惯导、高度表信息融合,构造多速率扩展Kalman滤波器进行了阐述. 通过自主开发的"UCAV自主着陆实时仿真验证平台"对该方案进行仿真,得到了满意的结果.