缺口件振动疲劳寿命预测的频域法和时域法的比较与分析

以缺口件为研究对象,在窄带信号下分别采用频域法和时域法预测缺口件的振动疲劳寿命。频域法选用Rayleigh模型和Dirlik模型作为应力变程概率密度p(S)模型,采用Miner累积损伤准则计算振动疲劳寿命。时域法通过傅里叶逆变换将结构危险点处的应力响应功率谱密度函数转为应力-时间历程样本,采用雨流循环计数结合Miner累积损伤准则,得到一个疲劳寿命样本,计算多个样本取均值作为振动疲劳寿命。计算结果和试验结果表明:时域法的精度较高,但工作量较大;选用 Rayieigh 模型和 Dirlik 模型的频域法预测寿命精度接近,比时域法的精度略差,但工作量较小。     

本地标准时间频率的产生与保持

近年来，地方协调时UTC(BIRM)守时能力稳步提升，截至目前，UTC(BIRM)与UTC的相对频率偏差优于3E-14，时间偏差优于20ns。本文概括介绍了守时系统的组成，本地频率驾驭与主备同步技术，以及TA(BIRM)算法研究等。     

Impact time control using biased proportional navigation for missiles with varying velocity

A feasible guidance scheme with impact time constraint is proposed for attacking a stationary target by missiles with time-varying velocity. The main idea is to replace the constant velocity with the future mean velocity; therefore, the existing time-to-go estimation algorithm of the proportional navigation guidance law can be improved to adapt to varying conditions. In order to obtain the prediction of the velocity profile, the velocity differential equation to the downrange is derived, which can be numerically integrated between the current downrange and the target position by the on-board computer. Then, a third-order polynomial is introduced to fit the velocity profile in order to calculate the future mean velocity. At the beginning of each guidance loop, the future mean velocity is predicted and the time-to-go information is updated, based on which a novel biased proportional navigation guidance law is established to achieve the impact time constraint. Finally, numerical simulation results verified the effectiveness of the time-to-go estimation algorithm and the proposed law.     

Analysis of BDS-3 distributed autonomous navigation based on BeiDou system simulation platform

Satellite autonomous navigation is an important function of the BeiDou-3 navigation System (BDS-3). Satellite autonomous navigation means that the navigation satellite uses long-term forecast ephemeris and Inter-Satellite Link (ISL) measurements to determinate its own spatial position and time reference without the support of the ground Operation and Control System (OCS) for a long time to ensure that the navigation system can normally maintain the time and space reference. This paper aims to analyze the feasibility of distributed autonomous navigation algorithms. For the first time, a ground parallel autonomous navigation test system (GPANTS) is built. The performance of distributed autonomous navigation is then analyzed using the two-way ISL ranging of BDS-3 satellites. First, the BDS simulation platform and the GPANTS are introduced. Then, the basic principles of distributed satellite autonomous orbit determination and time synchronization based on ISL measurements are summarized. Preliminary evaluation of the performance of the BDS-3 constellation autonomous navigation service under ideal conditions through simulation data. Then the performance of autonomous navigation for 22 BeiDou-3 satellites using ISL measurements is evaluated. The results show that when satellites operate autonomously for 50 days without the support of any ground station, the User Range Error (URE) of autonomous orbit determination is better than 3 m, and the time synchronization accuracy is better than 4 ns.     

紫外-短波红外航天遥感探测器光电性能测试装置的研制和标定

为解决紫外-短波红外探测器光电性能测试和评价问题,研制了一套探测器的光谱响应、时间响应和偏压响应测试装置,为紫外-短波红外探测器的光谱响应和光电特性参量测试提供测试装置和评价依据,以便评价其综合性能指标是否满足设计和使用要求。介绍了测试装置的研制和标定过程,该测试系统由宽光谱复合光源、样品室、单色仪、锁相放大器、标准探测器等构成,实现了200～2 500 nm光谱范围内光电探测器绝对/相对光谱响应度、量子效率、归一化探测率、频响特性、偏压响应度和时间响应参量的测试功能。最后分析了照明光斑波长校准和光谱辐射照度标定的重要性,并给出标定方法和结果。     

基于CDMA-TDD系统的联合功率控制算法

针对常规的码分多址CDMA (Code Division Multiple Access)时分双工TDD (Time Division Duplex) 系统功率控制算法存在的缺陷,提出了一种基于通信链路当前状态信息的联合功率控制算法.从理论上推导了联合功率控制方程.在新算法中,所有移动终端调整后的新发射功率值是基于共同的通信资源得出的.分配在同一时隙的各个移动终端的功率调整是基于通信链路的当前状态信息,其中包括各移动终端下一步使用的调整后的新发射功率值.使得各移动终端能够平等的共享链路资源,加快功率控制的收敛.通过建立功能模型,验证和评估了这一新的算法.仿真结果表明这一新的功率控制算法优于当前的常规算法,能减小接收端信噪比动态范围,降低干扰信号强度,提高能量效率和系统容量.     

Neal-Smith时域PIO预测准则及应用

基于Neal-Smith频域准则,Neal-Smith时域准则(TDNS, Time Domain Neal-Smith criterion)是另一重要的固定翼飞机驾驶员诱发振荡(简称PIO)预测准则,其无需对人机系统的非线性进行任何假设和简化.以某机型为模型,采用TDNS,通过俯仰角闭环操纵误差信号与目标捕获时间之间的关系来同时预测I、II型驾驶员诱发振荡,同时分析了不同速率限制环节对预测结果的影响,基于误差信号的均方差及其二次偏导数,得到了TDNS准则一般计算方法及各个影响因素的关系.结果表明,TDNS准则的计算方法可行、直观、高效.     

单站GPST/GLONASST时差监测研究

精密定时/授时是全球导航卫星系统（GNSS）中重要的一部分。每个GNSS都维护有自己的参考时间,尽管他们都向协调世界时溯源,但各系统间可能存在着几十甚至几百ns的偏差。要充分利用各个系统的卫星资源进行统一定位和授时服务就必须准确确定各个系统间的时差。文中分析了基于空间信号法的单站时差监测原理,提出了利用GPS/GLONASS多模双频接收机输出的两个系统的观测数据、导航电文以及标准共视数据监测GLONASST与GPST的时差方法。利用BIPM T公报公布的相关数据对130d的时差监测结果进行了评定。结果表明,130d中,时差监测结果消除系统差后与T公报结果最大偏差优于8ns,证明监测结果是有效可用的。     

航材消耗的时间序列分析

本文采用时间序列分析法对某种航材故障率进行预测,用移动平均法消除时间序列的长期趋势和周期变动,然后按月平均法求出季节指数,并对季节指数进行调整,然后根据拟合的趋势方程对此种航材的故障率进行预测.其结果能为航材的可靠性保障提供理论依据.     

军机无维修待命时间试飞验证方法研究

以工程应用为出发点,提出了试验机技术状态确定的依据、单次无维修待命时间验证成败判据、特殊气象条件下试验数据处理方法、无维修待命时间验证评估模型.在此基础上,以某型歼击机为例给出了试飞阶段无维修待命时间验证方案设计方法.该方法工程应用性强,可作为试飞阶段外场开展无维修待命时间验证的依据.