民机复合材料典型结构件检修间隔的概率分析

民机复合材料结构在服役过程中的损伤主要来源于意外冲击,会大幅度降低结构强度,影响飞机安全.以某型飞机外翼为例,考虑运行过程中意外冲击损伤的产生、载荷超限和维护过程中损伤的漏检等因素,采用概率分析方法对结构失效概率进行分析,并计算详细目视检测方法对应的检修间隔.结果表明,计算得到的检修间隔略大于工程实际中"4C"值.此概率分析方法用来确定复合材料结构件检修间隔是可行的,并可以实现检修间隔的动态化调整.     

Suggestion for aircraft flying qualities requirements of a short-range air combat mission

Owing to the lack of a direct link with the operations in short-range air combat,conventional aircraft flying qualities criteria are inappropriate to guide the design of a task-tailored flight control law.By applying the mission-oriented flying qualities evaluation approach,various aircraft with different control law parameters are evaluated on a ground-based simulator.This paper compares the evaluation results with several conventional flying qualities criteria,and discusses the appropriate parameter combination to reflect the flying qualities requirements of short-range air combat,The comparison and analysis show that a short-range air combat mission requires a higher minimum short period mode natural frequency and a smaller maximum roll mode time constant,and allows a lower minimum pitch attitude bandwidth and a higher maximum short period mode damp ratio than those of conventional flying qualities criteria.Furthermore,a combination of the pitch attitude bandwidth,the pitch attitude magnitude at the bandwidth frequency,and the pitch attitude transfer function gain can define the flying qualities requirements of short-range air com bat.The new metric can successfully predict the flying quality levels of aircraft in a short-range air combat mission.     

Modeling irregular small bodies gravity field via extreme learning machines and Bayesian optimization

Close proximity operations around small bodies are extremely challenging due to their uncertain dynamical environment. Autonomous guidance and navigation around small bodies require fast and accurate modeling of the gravitational field for potential on-board computation. In this paper, we investigate a model-based, data-driven approach to compute and predict the gravitational acceleration around irregular small bodies. More specifically, we employ Extreme Learning Machine (ELM) theories to design, train and validate Single-Layer Feedforward Networks (SLFN) capable of learning the relationship between the spacecraft position and the gravitational acceleration. ELM-base neural networks are trained without iterative tuning therefore dramatically reducing the training time. Analysis of performance in constant density models for asteroid 25143 Itokawa and comet 67/P Churyumov-Gerasimenko show that ELM-based SLFN are able learn the desired functional relationship both globally and in selected localized areas near the surface. The latter results in a robust neural algorithm for on-board, real-time calculation of the gravity field needed for guidance and control in close-proximity operations near the asteroid surface.     

航母编队网络化协同反导装备体系建设探讨

随着信息技术的发展,航母编队建设网络化协同作战体系,成为提高其作战能力的必由之路。在借鉴美军网络化作战装备体系建设的基础上,对航母编队网络化协同反导作战装备体系的构成和主要功能进行了阐述,并对未来向着"以网络为中心"的发展方向进行了探讨。     

Multi-state autonomous drilling for lunar exploration

Due to the lack of information of subsurface lunar regolith stratification which varies along depth, the drilling device may encounter lunar soil and lunar rock randomly in the drilling process. To meet the load safety requirements of unmanned sampling mission under limited orbital resources, the control strategy of autonomous drilling should adapt to the indeterminable lunar environments. Based on the analysis of two types of typical drilling media (i.e., lunar soil and lunar rock), this paper proposes a multi-state control strategy for autonomous lunar drilling. To represent the working circumstances in the lunar subsurface and reduce the complexity of the control algo-rithm, lunar drilling process was categorized into three drilling states:the interface detection, initi-ation of drilling parameters for recognition and drilling medium recognition. Support vector machine (SVM) and continuous wavelet transform were employed for the online recognition of dril-ling media and interface, respectively. Finite state machine was utilized to control the transition among different drilling states. To verify the effectiveness of the multi-state control strategy, drilling experiments were implemented with multi-layered drilling media constructed by lunar soil simulant and lunar rock simulant. The results reveal that the multi-state control method is capable of detect-ing drilling state variation and adjusting drilling parameters timely under vibration interferences. The multi-state control method provides a feasible reference for the control of extraterrestrial autonomous drilling.     

数控机床及工装的发展与创新设计

在现代数控加工中,由于被加工件的精度要求以及复杂度不断提高,传统加工系统无法满足使用需求,为解决这一问题,数字控制系统的核心算法以及驱动系统得到了快速发展,一些创新机构也应用到了数控机床的整机结构设计中.这些解决措施大幅提升了被加工件的精度和表面质量,促进了市场上一系列新型数控机床的出现,如复合机床、镜像铣削机床等,与之配合的新型加工工装技术也取得了相应的突破.     

面向客机总体设计的涡扇发动机分析模型

建立一种用于估算涡扇发动机特性的工程分析模型，该模型以涡喷发动机推力估算模型与涡扇发动机效率分析方法为基础，引入高涵道比涡扇发动机的循环分析方法进行修正。利用该模型可以获取涡扇发动机的推力和油耗特性，进而考察总体循环参数对发动机性能的影响。通过与文献验证数据对比，判定了分析模型的精度。该模型只需要输入少量参数就可以快速完成计算过程，适合于飞机总体设计阶段，可以评估涡扇发动机参数对飞机性能的影响。     

飞机重心位置的计算分析方法

飞机重心位置对飞机的安定性和操纵性影响很大.不在飞机重心允许范围内装货或载客时,会使飞机操纵性和安定性变差,影响飞行安全.飞机重心位置计算分析是新型飞机研制、现役飞机加改(换)装设计等工程中必不可少的一个重要环节.以某型现役飞机进口短波单边带电台换装国产短波自适应/跳频电台工程作为研究对象,研究了基于力矩平衡法的飞机重心位置计算方法,计算了该型飞机换装短波电台后空机重心位置.计算结果表明,该型飞机进口短波电台换装国产短波电台后,空机状态下的重心位置满足重心允许范围要求.     

气动钣金快速成形机的研制

针对电动钣金成形机制造成本高、效率低、易产生死点的问题,提出一种采用气液增力装置代替液压传动系统的气动钣金成形机设计方案。气液增力装置采用精密气压转换阀控制,实现行程平稳控制和加工成形过程平稳加载,显著提高了生产效率;配套研制的多种无齿收缩成形模具,可加工不同形状钣金件并获得更好的表面质量。该技术在钣金快速成形方面的研究处于国内领先水平,已获得3项国家专利。     

分数槽集中绕组永磁同步电机设计与分析

分数槽集中绕组永磁同步电机由于转矩密度高、弱磁性能好、齿槽转矩小和效率高等特点,广泛应用于航空航天、电动汽车等领域。本文研究了机载雷达伺服系统用分数槽集中绕组永磁同步电机,建立了电机的解析模型,分析了长径比、裂比、磁密系数等设计参数对电机性能的影响规律。结果表明,电机的输出转矩和质量分别与定子外径D3os,D2os成正比,绕组端部比重与长径比λ成反比,综合转矩密度和绕组端部比重两个因素,λ宜在0.2~0.4范围内选择。当定子裂比γ增加时,转矩密度先增大后减小,为使转矩密度最大,γ宜在0.6~0.8范围内选择。当磁密系数χ增加时,输出转矩先增大后减小,为使输出转矩最大,χ宜设计在1.75附近。基于理论分析和仿真计算,文中设计并加工了一台45槽38极分数槽集中绕组永磁同步电机,最后通过实验测试了其性能。