Reliable flight performance assessment of multirotor based on interacting multiple model particle filter and health degree

Multirotor has been applied to many military and civilian mission scenarios. From the perspective of reliability, it is difficult to ensure that multirotors do not generate hardware and software failures or performance anomalies during the flight process. These failures and anomalies may result in mission interruptions, crashes, and even threats to the lives and property of human beings. Thus, the study of flight reliability problems of multirotors is conductive to the development of the drone industry and has theoretical significance and engineering value. This paper proposes a reliable flight performance assessment method of multirotors based on an Interacting Multiple Model Particle Filter (IMMPF) algorithm and health degree as the performance indicator. First, the multirotor is modeled by the Stochastic Hybrid System (SHS) model, and the problem of reliable flight performance assessment is formulated. In order to solve the problem, the IMMPF algorithm is presented to estimate the real-time probability distribution of hybrid state of the established SHS-based multirotor model, since it can decrease estimation errors compared with the standard interacting multiple model algorithm based on extended Kalman filter. Then, the reliable flight performance is assessed with health degree based on the estimation result. Finally, a case study of a multirotor suffering from sensor anomalies is presented to validate the effectiveness of the proposed method.     

数值仿真技术在热真空试验中的应用

由于热真空试验中温度测点有限，且关键部位布置困难，不能反映试验过程部件整体和关键部位的温度结果，导致试验有效性和产品安全性难以判断。通过数值仿真技术对试验过程进行模拟，得到所有部件详细温度场，验证试验有效性与产品安全性；发现影响产品温度分布的因素，研究提高产品可靠性措施。通过对某天线热真空试验过程模拟，得到天线详细温度场，并发现产品散热板安装＂不紧密＂缺陷，是影响天线温度均匀性的＂关键点＂。     

基于数值模拟的超塑成形压力—时间曲线计算机辅助设计

确定压力随时间变化的关系曲线对于超塑成形工艺设计非常重要，本文在超塑成形压力计算时引入能量消耗控制策略，提出了一种压力－时间（Ｐ－Ｔ）曲线设计方法即恒能耗率法，实现了基于有际元数值模拟的超塑成形Ｐ－Ｔ曲线计算机辅助设计，文中对有关的压力控制算法及算式进行了较详细的介绍和推导，分别给出了半球壳自由胀形和圆筒形凹模约束成形过程的Ｐ－Ｔ曲线设计计算实例，并对计算结果进行了讨论，本文的研究拓宽了刚粘塑性有     

Coupling damage and reliability model of low-cycle fatigue and high energy impact based on the local stress–strain approach

Fatigue induced products generally bear fatigue loads accompanied by impact processes,which reduces their reliable life rapidly. This paper introduces a reliability assessment model based on a local stress–strain approach considering both low-cycle fatigue and high energy impact loads.Two coupling relationships between fatigue and impact are given with effects of an impact process on fatigue damage and effects of fatigue damage on impact performance. The analysis of the former modifies the fatigue parameters and the Manson–Coffin equation for fatigue life based on material theories. On the other hand, the latter proposes the coupling variables and the difference of fracture toughness caused by accumulative fatigue damage. To form an overall reliability model including both fatigue failure and impact failure, a competing risk model is developed. A case study of an actuator cylinder is given to validate this method.     

民用飞机维修目标与要求的指标体系研究

维修目标与要求(MORs)是为了能够并便于对产品进行维修而对航空器设计、维修和保障所提出的目标与要求,是设计、使用、维修、成本、效率等多种因素的综合权衡结果,也是维修工程学要实现的具体要求和指标。本文立足民用飞机,结合自身民机维修经验,从MORs指标确定的风险、过程、指标的分类等方面对MORs及其指标进行了研究。     

基于支持向量机的航空发动机性能衰退指标预测

针对航空发动机性能衰退状态的趋势预测问题,基于非线性支持向量机回归建立了发动机性能衰退指标的预测模型,给出了反映其性能衰退的综合指标。利用该模型对发动机的性能衰退指标进行了预测分析,并与神经网络模型预测结果进行了比较。结果表明:支持向量机回归预测模型能更准确地对发动机的未来状况进行预测。     

Ψ(t)R_0──复合非时齐单调Poisson过程模型结构可靠性当量正态设计

本文讨论抗力Ψ（t）R0，荷载效应为强度函数λ（t）＝ae－bt，（t≥0，a，b＞0为实数）的复合非时齐单调Poisson过程结构可靠性模型。获得非时齐非增Poisson过程和非时齐非降Poisson过程样本函数最大值概率分布及统计参数估计。同时获得抗力Ψ（t）R0，其中R0～N（μR0，σ2R0）为初始随机变量，Ψ（t）＞0是t的单调递减连续实函数；荷载效应为复合非时齐单调Poisson过程模型结构可靠性当量正态设计表达式。     

扇区繁忙时段交通流的不均衡度量化研究

以容流量及拥挤度等指标进行的空中交通运行评价无法全面反映空中交通的实际运行状况.在依据重要点对航路段进行分组的基础上,通过计算超容比,确定了扇区繁忙时段,基于多项式二次拟合分析了超容比与基尼系数以及泰尔指数之间的数量关系,基于3σ原则确定了不同超容比情况下的理想不均衡度的取值范围.应用方法对厦门1号扇区的实际运行数据进行了计算分析,验证了不均衡度量化方法的适用性.     

The comprehensive aerospace index (CASI): Tracking the economic performance of the aerospace industry

In this paper, we described the Comprehensive AeroSpace Index (CASI), a financial index aimed at representing the economic performance of the aerospace industry. CASI is build upon a data set of approximately 20 years of daily close prices set, from January 1987 to June 2007, from a comprehensive sample of leading aerospace-related companies with stocks negotiated on the New York Exchange (NYSE) and on the over-the-counter (OTC) markets. We also introduced the sub-indices CASI-AERO, for aeronautical segment, and CASI-SAT, for satellite segment, and considered the relation between them. These three indices are compared to others aerospace indices and to more traditional general financial indices like DJIA, S&P500 and Nasdaq. Our results have shown that the CASI is an index that describes very well the aerospace sector behavior, since it is able to reflect the aeronautical segment comportment as well as the satellite one. Therefore, in this sense, it can be considered as a representative index of the aerospace sector. Moreover, the creation of two sub-indices, the CASI-AERO and the CASI-SAT, allows to elucidate capital movements within the aerospace sector, particularly those of speculative nature, like the dot.com bubble and crash of 1998–2001.     

卫星用电容器的性能、特点和应用可靠性

介绍星用电容器选用要点、失效实例，以及如何提高固但、液但、陶瓷电容器的应用可靠性。还谈及四个问题：①固钽不能用在电源滤波器中；②因钽的可靠性与使用线路阻抗有关，如果线路阻抗越小则可靠性越差；③液钽易发生振动失效，有些在振动激励下可能成为瞬息电势源（间歇短路）；④多层陶瓷电容器的低压失效。分析了这些特殊失效现象及失效机理，提出可能采用的筛选方法。