基于足间距信息辅助的行人三维惯性定位算法

针对行人惯性导航系统误差随时间累积致使定位精度严重下降的问题,提出了一种基于足间距信息辅助的行人三维惯性定位算法。该算法在零速修正算法的基础上,利用足部安装的超声波测距模块实时测量行人双足相对距离,构建了基于超声测距的足间距约束模型,通过随机森林算法实现行人运动模式识别,并针对上下楼梯场景,利用台阶高度和足间距信息进行高度解算,最终实现行人三维惯性定位。在实际路线上开展了三维定位实验,数据显示,所提算法平面闭环误差为总路程的0.64%,与零速修正算法相比下降了55.56%,高度误差为0.06 m,与零速修正和气压计联合算法相比下降了64.70%,能够实现导航误差在总路程的0.50%以内的三维定位。实验结果表明,所提算法具有良好的工程应用价值。     

基于足部安装MIMU的行人导航系统设计

针对无卫星环境中行人导航定位需求,设计了一种基于足部安装MIMU的行人导航系统,重点研究了行人导航鞋传感器选型及样机设计流程;并在此基础上设计了基于零速修正和航向修正的行人导航算法,研究了零速区间内最优航向角的提取方法,实现了对瞬时磁干扰产生的磁航向角的有效判断。最后,利用设计的行人导航系统开展了三维空间航迹测试实验,实验结果表明,在不增加高度约束的条件下,该行人导航系统定位精度为0.33%,能够满足坡路环境中行人的定位需求。     

基于自包含传感器的单兵导航系统设计

针对无卫星信号环境中单兵人员导航定位需求,设计了一种基于自包含传感器的单兵导航系统,重点研究了惯性传感器和压力传感器组合的零速区间检测算法,并通过对单兵导航系统背景磁场误差进行补偿来计算航向角,实现了速度观测量和航向观测量的准确提取。在此基础上,采用Kalman滤波器对系统状态误差进行估计,并对惯性导航解算结果中的累积误差进行修正。最后,在实际路线上开展了单兵导航系统定位实验,实验结果表明,行人在矩形路线终点位置处的位置误差为0.42m,占行走总路程的0.33%,从而证明了零速修正和航向修正能有效提高单兵导航系统的定位精度。     

一种优化的零速检测行人导航算法

针对军事上对单兵定位和民用领域为行人提供位置服务的需求,提出了足部固定MIMU的行人导航算法.利用人体行走过程中脚部与地面相接触的静止时间段,采用零速更新(ZeroVelocity Update,ZVU)对INS继续对准或标定,而零速检测又是实现零速修正的基础.研究对比了在足部固定MIMU进行零速检测的常用方法,针对常用算法阈值自适应性差,无法检测步速变化转弯等一些异常情况对行人零速检测产生误判等问题,提出优化的零速判断算法,使得加速度计信号和陀螺仪信号综合应用到零速检测.最后,利用改进算法设计行人室内平地正常行走(大约5km/h)包含步速变化和转弯过程的实验.实验结果表明,优化的零速检测算法相比之前的常用算法,能更准确地检测零速并进行修正,对导航轨迹和导航误差有更好的修正效果.     

基于零速修正的行人导航关键技术及研究进展

在室内等卫星导航受限场景下，可采用MEMS惯性传感器对行人进行自主导航定位。采用MEMS惯性传感器的行人自主导航技术主要包括基于步长估计的行人航位推算和基于零速修正的行人导航算法两种方式。首先介绍了两种方式的基本原理，然后重点分析了零速修正的行人导航算法，阐述了相关的关键技术和研究进展。最后，对行人自主导航未来的发展趋势进行了展望，并指出了需要重点关注的技术难点。     

基于UWB/SINS组合的行人导航研究

在特殊环境下全球定位系统(GPS)信号强度被严重削弱,此时基于GPS技术的导航设备将受到严重影响。针对不依赖GPS的行人导航定位需求,提出了一种基于微机电捷联惯导系统(SINS)与超宽带(UWB)定位系统相结合的行人导航方法。该系统由捷联惯导系统与超宽带定位系统组成,行人导航算法在传统的捷联算法的基础上引入了零速修正技术用于检测零速时刻,并使用阈值法剔除了超宽带错误信息,通过联邦Kalman滤波融合了零速、位置和航向信息,并对系统速度、位置、航向进行了校正。行人导航实验表明,该方法能够提升系统定位精度,并进一步加强系统的稳定性与可靠性。     

基于MIMU的适应多步态的步行导航算法

针对目前国内外步态导航算法中引入的零速检测大都不能很好的对多种步态的行走进行辨识的问题,提出了基于低成本MIMU（微惯性测量单元）、且能兼容多种步态的步行导航算法。算法通过采集安置在行人脚部MIMU输出的测量信息,用捷联惯性积分算法进行导航解算。其间,提出一种新的零速检测方法对行走时变化的步速和步型进行准确辨识,进而找到脚步的零速时刻点,并通过设计的扩展卡尔曼滤波（EKF）对导航解算结果进行零速修正（ZUPT）,实现系统的反馈。最后进行两组实验对算法验证。结果表明,该步态导航算法能对行走时的多步态问题有很好的兼容性,零速修正时刻辨识准确度高,两组实验的导航解算误差均达到0.6%以内,进一步提高了步态导航算法的精度和实用性。     

基于人体运动学辅助的可穿戴式行人导航系统

针对行人导航定位问题,研究了基于人体运动学辅助的可穿戴式行人导航系统实现的关键技术。首先基于人体运动学原理构建了零速检测模型,使用最优综合判断条件有效检测出对应的零速时刻,实时进行速度和姿态的更新修正。在检测到零速时刻时,将速度误差、位置误差作为观测量,经Kalman滤波估计惯导系统误差并进行反馈校正,抑制惯导系统的误差,提高导航定位精度。研制了集信息采集、数据传输、导航解算与监控显示于一体的可穿戴式行人导航系统,可对行人的运动状态进行实时监控。所设计的基于人体运动学辅助的可穿戴式行人导航系统,平均定位误差小于行走距离的1.1%,最大不超过1.7%,验证了本系统的可靠性和适用性。     

基于室内合作场景智能识别的行人导航算法

基于足绑式惯性测量单元(IMU)的惯性导航系统被广泛应用于行人导航中,其通过零速修正(ZUPT)算法可对速度估计误差进行较好的补偿,然而其位置误差会随时间发散。针对于此,提出了一种基于室内合作场景智能识别的行人导航算法。通过随机森林算法,对行人在室内平地步行、上楼梯、下楼梯等不同步态进行训练与辨识,并结合室内先验地图对行人导航的结果进行校正。通过实验表明,行人在室内行走1100m时最大定位误差为1.85m(总行程0.17%),相对无场景识别的方法精度提高了6倍,可以有效提高行人导航精度。     

足绑式PNS自适应滑动平均零速区间检测方法

针对足绑式个人导航系统（PNS）中,传统的滑动平均算法对零速区间检测的延迟问题,设计了一种基于自适应滑动平均算法,对零速区间进行检测。首先对比力模值和角速率模值进行滑动平均,根据平均后数据的变化趋势,通过比较样本方差,设置一个自适应的滑动时间窗口来判断行人是否静止。该方法既能避免由于平滑算法带来的延时问题,又能够消除抖动干扰造成的误检,从而得到准确的零速区间。行走实验验证了本文方法的有效性,自适应滑动平均算法的导航精度提高了50%。     

绕飞慢自旋小天体的航天器运动分析

针对可以用三轴椭球体近似建模的小天体,给出了非球形引力势函数,建立了航天器绕飞小天体的轨道动力学方程。利用Jacobi积分常数绘制了探测器在小天体周围的零速度曲线,并分析了探测器的可能运动区域,给出了航天器不碰撞小天体的边界条件。针对绕飞慢自旋小天体的情况,基于平均轨道根数的近似解分析了小天体扁率和椭率的摄动影响,并给出了几条冻结轨道及其稳定条件。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.