光纤惯导角度随机游走误差传播特性研究

角度随机游走是光纤陀螺的一个重要技术指标,也是高精度光纤惯导系统的一项重要误差源。为了深入了解角度随机游走误差对系统精度的影响,从统计角度研究了该误差在导航过程中的传播特性。通过将角度随机游走对系统的影响等效为不相关的随机脉冲序列激励下的系统输出,推导了角度随机游走作用下导航误差的理论公式并进行了仿真验证。结果表明,所给出的理论表达式能够很好地描述角度随机游走误差的传播规律。通过解析表达式,可以在任意时间段对任何一只陀螺角度随机游走造成的系统误差进行定量分析,这对于系统性能评估、误差分析和设计工作都具有重要意义。     

Compressive properties of homemade carbon fiber composite laminates with delamination defect

Large numbers of aircraft composite structures were researched, and the distribution of delamination sizes and though thickness positions in the composite laminates were investigated. An experiment was conducted to probe into the effect of delamination sizes and through thickness positions on the compressive strengths of laminates with single embedded circular delamination with the most dangerous delamination sizes and positions defined from the distribution. A shell model was established for compressive strength prediction, and the virtual crack closure technique (VCCT) was employed for the strain energy release rate calculation. The finite element (FE) prediction was in good agreement with the experimental measurements, for the predicted compressive strengths stood within 10% error of experimental results. It was observed that the compressive strength was highly effected by the delamination size, while the though thickness position of delamination did not have significant effect on the compressive strength.      

电动舵机减速器传动特性误差分析与补偿研究

在电动舵机减速器的传动特性测试实验中,由于机械安装,轴承摩擦和电机驱动器非线性等原因造成的测量误差会折算到传动比测量误差中并降低精度。本文以减速器为研究对象,通过动力学方程建立了该系统的数学模型,通过理论分析将机械安装与轴承摩擦作为已知的系统误差,提出一种根据仿真结果获得补偿量,对实测数据进行预处理从而提高传动比测量精度的新方法。计算结果说明此方法能在一定程度上补偿电机驱动器非线性带来的测量误差。     

Numerical simulation of viscous flows with adaptively refined Cartesian grid

Quadtree-based Cartesian grid was automatically generated from specified geometry.Adaptive refinements were performed according to geometric parameters and solution of flow field.An altered CCST (curvature corrected symmetry technique) approach was proposed to apply solid wall boundary conditions.Driven flows in a square cavity and flows around NACA0012 airfoil were simulated and compared with the result of published structured grid and stretched Cartesian grid.The results show that solid wall boundary condition are accurately applied by current altered CCST approach,while incompressible/compressible subsonic,transonic and supersonic viscous flows are adequately simulated with adaptively refined Cartesian grid.      

V肋对尾缘劈缝气膜冷却特性的影响

采用压敏漆技术和瞬态热色液晶技术研究了V肋对尾缘劈缝表面气膜冷却特性的影响,获得了不同吹风比及V肋宽度下2种不同尾缘劈缝表面形状的气膜冷却效率和对流换热系数分布的试验数据,并采用净热流密度值评估对比了带有V肋的劈缝结构的综合冷却性能。试验结果表明：V肋的加入对未扩张型劈缝表面的气膜覆盖产生了不利影响,在小吹风比工况下,V肋宽度对面积平均气膜冷却效率无明显影响,相同V肋宽度结构下,未扩张型劈缝表面的气膜冷却效率始终高于扩张型劈缝表面的;V肋宽度对劈缝表面换热强度的影响不明显,V肋在未扩张劈缝表面结构上展现出的强换热性优于扩张型劈缝表面结构;带有V肋的尾缘劈缝冷却结构可有效增大6.9%~26.6%的净热流密度值,V肋宽度对其无明显影响,小吹风比工况下宜将V肋应用于未扩张的劈缝表面结构,大吹风比工况下无需考虑劈缝表面形状。     

Orbit determination by genetic algorithm and application to GEO observation

This paper demonstrates an initial orbit determination method that solves the problem by a genetic algorithm using two well-known solutions for the Lambert’s problem: universal variable method and Battin method. This paper also suggests an intuitive error evaluation method in terms of rotational angle and orbit shape by separating orbit elements into two groups. As reference orbit, mean orbit elements (original two-lines elements) and osculating orbit elements considering the J2 effect are adopted and compared. Our proposed orbit determination method has been tested with actual optical observations of a geosynchronous spacecraft. It should be noted that this demonstration of the orbit determination is limited to one test case. This observation was conducted during approximately 70 min on 2013/05/15 UT. Our method was compared with the orbit elements propagated by SGP4 using the TLE of the spacecraft. The result indicates that our proposed method had a slightly better performance on estimating orbit shape than Gauss’s methods and Escobal’s method by 120 km. In addition, the result of the rotational angle is closer to the osculating orbit elements than the mean orbit elements by 0.02°, which supports that the estimated orbit is valid.     

基于可不断电维修的双机容错系统

对单个单片机控制系统可靠性不高的问题,提出了一种由双单片机构成容错系统的实现方法.在该系统中,用串行通讯技术,通过采集对方I/O输出,与自身的I/O输出值作比较,实现双单片机的故障互检;利用地址译码技术,设计仲裁切换模块,完成故障隔离;故障机修复后,通过回读对方执行程序的任务编号,达到双机同步控制,完成系统重构,实现对故障单元的不断电维修.通过对模拟机的实验表明,此控制系统能对运行中的错误实现实时的双机互检,且具有在线热插拔功能.     

航天器近距离相对运动的轨迹偏差分析

利用相对可达区(RRD)的概念对航天器在脉冲闭环控制方式下相对运动的轨迹偏差进行了分析。相对可达区是对航天器可能出现位置集合的一种几何描述。当航天器的状态误差服从高斯分布时,相对可达区可表示为随时间变化的误差椭球的集合。考虑航天器飞行过程中存在的不确定性因素,基于闭环控制系统下线性化的相对运动动力学模型,采用协方差分析描述函数法(CADET)对定义航天器误差椭球的协方差矩阵进行了分析,给出了根据协方差矩阵求解相对可达区包络的计算方法。通过将开环和闭环控制系统下的相对可达区包络与1 000次的Monte Carlo仿真结果进行比较,证明了偏差分析方法的适用性与有效性。     

捷联惯导系统在线标定综述

捷联惯导系统的部件直接固联在载体上,承受着载体工作过程中的恶劣环境,因此系统参数容易受到影响而变化,需要通过标定过程获得参数变化并进行补偿,从而修正捷联惯导系统精度。针对捷联惯导系统在线标定问题,阐述了国内外在线标定技术的发展,对在线标定问题中的重点技术如误差方程分析、可观测性分析和滤波技术进行了详细的介绍,最后,初步分析了捷联惯导系统在线标定技术的研究方向。     

数字音频技术(MP3)的压缩编码原理与制作方法

本文从音频压缩理论的角度,阐述MP3音频格式、压缩编码原理,同时介绍专业制作MP3的方法.