Relative Position and Attitude Control for Drag-Free Satellite with Prescribed Performance and Actuator Saturation

An adaptive prescribed performance control scheme is proposed for the drag free satellite in the presence of actuator saturation and external disturbances.The relative translation and rotation dynamics between the test mass and outer satellite are firstly derived.To guarantee prescribed performance bounds on the transient and steady control errors of relative states,a performance constrained control law is formulated with an error transformed function.In addition,the requirements to know the system parameters and the upper bound of the external disturbance in advance have been eliminated by adaptive updating technique.A command filter is concurrently used to overcome the problem of explosion of complexity inherent in the backstepping control design.Subsequently,a novel auxiliary system is constructed to compensate the adverse effects of the actuator saturation constrains.It is proved that all signals in the closed?loop system are ultimately bounded and prescribed performance of relative position and attitude control errors are guaranteed.Finally,numerical simulation results are given to demonstrate the effectiveness of the proposed approach.

Integrated modeling of spacecraft relative motion dynamics using dual quaternion

To realize high accurate control of relative position and attitude between two spacecrafts, the coupling between position and attitude must be fully considered and a more precise model should be established. This paper breaks the traditional divide and conquer idea, and uses a mathematical tool, namely dual quaternion to establish the integrated 6 degree-of-freedom(6-DOF) model of relative position and attitude, which describes the coupled relative motion in a compact and efficient form and needs less information of the target. Considering the complex operation rules and the unclarity of the current relative motion model in dual quaternion, necessary mathematical foundations are given at first, followed by clear and detailed modeling process and analysis. Finally a generalized proportion-derivative(PD) controller law is designed. The simulation results show that based on the integrated model established by dual quaternion, this control law can achieve a high control accuracy of relative motion.

Monocular Vision-based Two-stage Iterative Algorithm for Relative Position and Attitude Estimation of Docking Spacecraft

Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range ren- dezvous phases. This article proposes a two-stage iterative algorithm based on an inverse projection ray approach to address the relative position and attitude estimation by using feature points and monocular vision. It consists of two stages： absolute orienta- tion and depth recovery. In the first stage, Umeyama＇s algorithm is used to fit the three-dimensional （3D） model set and estimate the 3D point set while in the second stage, the depths of the observed feature points are estimated. This procedure is repeated until the result converges. Moreover, the effectiveness and convergence of the proposed algorithm are verified through theoreti- cal analysis and mathematical simulation.

Coseismic gravity and displacement changes of Japan Tohoku earthquake(Mw 9.0)

The greatest earthquake in the modern history of Japan and probably the fourth greatest in the last 100 years in the world occurred on March 11, 2011 off the Pacific coast of Tohoku.Large tsunami and ground motions caused severe damage in wide areas, particularly many towns along the Pacific coast. So far, gravity change caused by such a great earthquake has been reported for the 1964 Alaska and the 2010 Maule events. However, the spatial-temporal resolution of the gravity data for these cases is insufficient to depict a co-seismic gravity field variation in a spatial scale of a plate subduction zone. Here, we report an unequivocal co-seismic gravity change over the Japanese Island, obtained from a hybrid gravity observation（combined absolute and relative gravity measurements）. The time interval of the observation before and after the earthquake is within 1 year at almost all the observed sites, including 13 absolute and 16 relative measurement sites, which deduced tectonic and environmental contributions to the gravity change. The observed gravity agrees well with the result calculated by a dislocation theory based on a self-gravitating and layered spherical earth model. In this computation, a co-seismic slip distribution is determined by an inversion of Global Positioning System（GPS） data. Of particular interest is that the observed gravity change in some area is negative where a remarkable subsidence is observed by GPS, which can not be explained by simple vertical movement of the crust. This indicated that the mass redistribution in the underground affects the gravity change. This result supports the result that Gravity Recovery and Climate Experiment（GRACE） satellites detected a crustal dilatation due to the 2004 Sumatra earthquake by the terrestrial observation with a higher spatial and temporal resolution.

The Satellite’s On-Orbit Attitude System Error Compensation Technique Based on Stereo Models

According to the problem that the low measurement accuracy of TH-1 satellite star sensor, the low frequency and “slow drift” error which cannot be ignored in the attitude determination system, resulting in obvious random error in the horizontal position and elevation direction, and the change of the error with time and latitude, cannot be calibrated by the ground field of the real problem. In this paper, a low frequency detection model is established by using the principle of relative orientation, and the low frequency error is obtained by parallax elimination. Finally, the satellite attitude is compensated and the more accurate exterior orientation elements are obtained, thus improving the positioning accuracy and stability. The experimental results show that: the proposed methods are feasible, and by using the model to dynamically calibrate the exterior orientation angle elements on orbit, the plane and elevation errors of the ground points can be basically eliminated. The global uncontrollable positioning accuracy and stability of the photogrammetry satellite are improved.

NOTES ON THE LOG-BRUNN-MINKOWSKI INEQUALITY

Böröczky-Lutwak-Yang-Zhang proved the log-Brunn-Minkowski inequality for two origin-symmetric convex bodies in the plane in a way that is stronger than for the classical Brunn-Minkowski inequality.In this paper,we investigate the relative positive center set of planar convex bodies.As an application of the relative positive center,we prove the log-Minkowski inequality and the log-Brunn-Minkowski inequality.

Attribute Reduction in Interval and Set-Valued Decision Information Systems

In many practical situation, some of the attribute values for an object may be interval and set-valued. This paper introduces the interval and set-valued information systems and decision systems. According to the semantic relation of attribute values, interval and set-valued information systems can be classified into two categories: disjunctive (Type 1) and conjunctive (Type 2) systems. In this paper, we mainly focus on semantic interpretation of Type 1. Then, we define a new fuzzy preference relation and construct a fuzzy rough set model for interval and set-valued information systems. Moreover, based on the new fuzzy preference relation, the concepts of the significance measure of condition attributes and the relative significance measure of condition attributes are given in interval and set-valued decision information systems by the introduction of fuzzy positive region and the dependency degree. And on this basis, a heuristic algorithm for calculating fuzzy positive region reduction in interval and set-valued decision information systems is given. Finally, we give an illustrative example to substantiate the theoretical arguments. The results will help us to gain much more insights into the meaning of fuzzy rough set theory. Furthermore, it has provided a new perspective to study the attribute reduction problem in decision systems.

飞机复合材料机身壁板装配技术分析与展望

复合材料以其优异的综合性能在航空航天领域得到了大量应用,其应用范围逐渐从次承力结构向主承力结构扩展,包括在机身结构的组成方面,传统的金属组装壁板逐渐被复合材料整体壁板所取代。由于复合材料壁板具有不同于传统金属材料壁板的装配工艺特点,因此对其装配方法和装配工艺提出了新的要求。针对圆筒状机身复合材料机身壁板的装配过程,分别介绍了复合材料机身壁板大尺寸测量技术、复合材料机身壁板装配定位调姿技术和复合材料机身壁板的先进制孔连接技术,系统总结了近年来国内外相关研究进展和应用情况,指出了飞机大尺寸复合材料结构装配技术未来的研究与应用方向。

旋转机构零位姿态传感器设计及测量方法

面向新型旋转成像载荷姿态角测量需求,针对现有传感器无法同时测量无接触旋转机构零位三轴姿态角的问题,提出了一种基于光电传感的旋转载荷零位姿态测量方法,并研制了零位姿态传感器,使用光电传感器获取过零波形,采用最小二乘法得到过零时的时间信息,通过时间和转速获得精确的旋转角和定转子相对位移。在此基础上,通过坐标变换求解出零位时的三轴姿态信息。分析平台舱和旋转舱平动、转动对传感器的测量精度的影响,建立传感器测量误差与光源组件轴安装误差、采样误差、传感器安装误差等的理论模型,仿真分析各因素对零位测量误差的影响。搭建了磁悬浮旋转支撑机构测试平台,对比所设计零位姿态传感器测量结果与电涡流位移传感器和旋变传感测量结果,分析所设计传感器的测量精度。结果表明,所设计传感器位移测量误差均值不大于2.4μm,转动角度测量误差均值不大于3.7"。所设计传感器能够准确检测出定转子间隙变化时的零位姿态信息,可为高精度的载荷舱姿态控制提供参考。

基于纯加速度计的弹载GFIMU配置方案研究

为提高火炮弹丸远程精确打击所需姿态测量精度,考虑低成本小型化高过载需求,研究了基于纯加速度计的弹载无陀螺惯性测量单元(GFIMU)方案。针对加速度计偏心产生臂杆效应的机理,分析并选择基于9通道加速度计与12通道加速度计的GFIMU方案;以输出误差为优化目标,利用有约束多目标粒子群算法分别对9/12通道加速度计GFIMU位置配置进行寻优,随后建立了角加速度与角速度二次项的非线性状态空间方程,修正过程方程与量测方程的噪声相关性,设计了噪声相关条件下的角速度扩展卡尔曼滤波(EKF)估计方法。通过建立外弹道模型并加入典型的MEMS加速度传感器噪声进行仿真求解,结果显示建立的GFIMU理论上是有效的,能达到弹丸短时航姿解算所需精度需求。

基于双PSD的三维测角传感器精度分析

在机载光电转台、多自由度摇摆台等系统中,对于一些运动体与基座间没有确定的回转轴的柔性支撑、并联支撑平台,需要考虑非接触三轴角度测量方法,目前大部分的光电非接触三轴角度测量方案系统复杂,占用空间大,无法适用于如机载、星载等载荷对体积、质量敏感的场景。为此,文中提出了基于双位置敏感探测器(PSD)的非接触三轴角度测量方案,使用准直镜头汇聚、双面反射光楔反射,将光源在两片PSD上汇聚成像,利用PSD上的光斑位置坐标反解出三轴角度。描述了其工作原理以及传感器构成,分析了因两片PSD的相对位置偏移产生的误差,提出了对应补偿方法以减少焊装产生的PSD位置偏移对测量精度的影响。主要对采集的PSD模拟信号值的抖动噪声进行FIR滤波处理,分析了滤波器的相频响应特性,并在MCU中测量相位滞后时间以及滤波器的响应带宽,验证了该数字滤波器在系统内拥有较好的实时传输特性。自准直测量单元总质量为230 g,尺寸为50 mm×50 mm×50 mm。实验结果表明,34阶FIR滤波器将角度测量的误差减小至60%,在±2°测量范围内单轴测量时,方位角、俯仰角、横滚角的误差均方根分别为0.003°、0.007°、0.017°,组合测量时分别为0.006°、0.009°、0.021°,文中所提出的三维测角传感器精度较高,满足机载等场景的使用要求。

基于多传感器融合的轨检车构架位姿测量方法

针对轨道检查车构架运动会影响轨道几何检测系统测量精度的问题,提出一种基于多传感器融合的构架位姿测量方法。该方法利用加速度传感器和双轴倾角传感器采集构架位姿原始信号,通过构架中心位姿解算方法将多个传感器采集的原始信号进行融合解算,获取构架几何中心位姿。为了验证其准确性和适应性,利用该方法分别在实验室和国家铁道试验中心标定试验线上进行了验证试验和在轨试验,结果表明,以第95%分位数作为评估标准,该方法测量的构架中心横向、垂向位移、侧滚角和摇头角与标准值的误差分别小于0.88 mm、0.44 mm、0.07°、0.04°,该方法与轨检系统测得数据的差异分别小于0.99 mm、0.73 mm、0.08°。构架位姿测量方法可以准确测量轨检车构架位姿,运用于运营车辆,可辅助判别轨道病害,提高轨道检测效率。

基于高速综合检测列车的构架运动位姿分析

综合检测列车构架的运动位姿会影响检测系统测量的准确性,为获取检测系统所在构架运动位姿,提出一种基于多加速度计组合的位姿解算算法。对综合检测列车检测系统所在构架中心运动位姿进行测试分析,结果显示,在相同速度条件下,列车构架中心位姿结果具有较强的相关性;同时针对多加速度计组合位姿测量方法无法感知线路线形造成的姿态角变化问题,提出位姿补偿方案,并搭建试验模型进行验证。结果表明补偿后横向位移、垂向位移、侧滚角度、摇头角度、俯仰角度的位姿解算结果与试验台反馈结果具有很好的一致性。上述结果可为综合检测列车上搭载的检测系统运动状态下的测量精度分析提供支撑。

柱塞气举工艺下基于重力观测的MEMS全姿态位姿测量系统

为解决柱塞小体积自主高精度位姿测量的难题,针对柱塞气举工艺,设计了一种基于重力观测的微机电系统(MEMS)全姿态位姿测量系统。首先,利用柱塞工作过程中大部分时间不存在非重力运动加速度的特性,设计了基于重力观测的自主导航算法提高位姿测量精度;其次,考虑到柱塞垂直运动过程中俯仰翻转时无解的问题,设计了全姿态解算算法。最后,对所设计的位姿测量系统进行了实物实验。实验结果表明:所设计的位姿测量系统进行作业时,水平姿态精度不大于0.05°、航向漂移小于0.5°/h、短时位置精度不大于0.8 m,验证了该系统可解决柱塞目前存在的小体积自主高精度位姿测量难题。

基于改进April Tag技术的吊件空间位置与姿态监测方法

为了解决吊件位置与姿态的监测难题,基于改进的April Tag技术提出了一种吊件位姿视觉测量方法。该方法采用专用磁吸式标签固定方式,降低标签安装难度和要求;通过视觉测量吊件上的April Tag标签位置,结合吊件关键尺寸信息,基于空间坐标变换理论实现了吊件位置和姿态的测量;同时根据标签间的相对关系对测量结果进行数据校验,提高测量精度。对架空输电线路双平臂落地抱杆组塔吊装施工的吊件进行了位置与姿态测量试验。结果表明:本文方法能够有效准确实现吊件空间位置与姿态的测量。

复杂环境下GPS+BDS-3 PPP/INS紧组合算法性能分析

针对城市复杂环境下精密单点定位(PPP)连续高精度定位受限的问题,本文基于北斗三号全球卫星导航系统(BDS-3)与全球定位系统(GPS)双系统,利用PPP与惯性导航系统(INS)紧组合算法来改善城市复杂环境下定位性能。通过构建GPS+BDS-3双系统PPP/INS紧组合滤波模型,分别对GPS PPP、GPS+BDS-3 PPP、GPS PPP/INS紧组合、GPS+BDS-3PPP/INS紧组合4种方案在城区开阔、复杂环境下的定位、测速、定姿性能进行了分析和评估。实验结果表明,开阔环境下PPP/INS紧组合相比PPP定位精度略有提升;而在复杂环境下PPP/INS紧组合可显著解决PPP定位结果连续性和有效性较差的问题;引入BDS-3后,PPP/INS紧组合导航性能进一步提升,GPS+BDS-3 PPP/INS紧组合相比GPS PPP/INS紧组合,在东、北、天方向上,开阔环境下定位精度分别提升18.5%、32.7%、43.2%,复杂环境下定位精度分别提升35.9%、49.1%、56.5%。

煤矿井下全站仪定位与设备姿态角测量技术分析

以井下单棱镜智能掘进机器人系统为研究对象,介绍一种全站仪定位与设备姿态角测量技术。此技术主要采用全站仪实施设备定位和姿态角测量,可实现不同影响因素情况下单棱镜智能掘进机器人系统姿态角的快速测量分析。为检验全站仪定位与设备姿态角测量技术的应用可行性,采用工程应用试验进行测量分析,最终验证此技术可满足设备定位及姿态角测量控制需求。

基于振型邓氏相关系数组合指标的桥梁支座脱空检测研究

桥梁支座作为连接梁式桥上下部结构的纽带,发挥着传递力与位移的作用。桥梁支座脱空会给桥梁运营带来安全隐患。研究通过激光多普勒仪,在多种桥梁支座脱空工况下,对室内简支梁板桥进行模态测试,获取了梁板在不同工况下的自振频率和振型信息,引入灰度系统关联度理论,检验了振型邓氏相关系数组合指标在桥梁支座脱空检测中的有效性。结果显示该指标能较好地识别出外侧的支座脱空,为现场桥梁支座脱空检测提供理论支撑,结果以期为类似工程提供参考。

基于视觉/惯导的掘进机实时位姿测量方法研究

针对煤矿井下掘进机实时位姿自动检测的难题,通过分析比较现有几种位姿测量方法的优缺点,提出了一种基于视觉/惯导的掘进机位姿组合测量方法。该方法通过激光捷联式惯导系统得到掘进机的姿态信息、单目视觉测量掘进机的位置信息,从而实现掘进机实时位姿的5自由度测量。依托大柳塔煤矿的快掘设备对该方法进行了实验验证。结果表明,姿态测量精度为0.1°,静态漂移的标准差不大于0.25°,位置定位精度优于1cm。该方法能够用于掘进机实时位姿测量,具有广阔的工程应用前景。

目标飞行器位置姿态的光学测量

本文回顾了航天器交会对接过程中,用光学方法测量目标飞行器位置姿态的已有工作,提出一种更优算法,给出了相应数学仿真结果。