Optimization on conventional and electric air-cycle refrigeration systems of aircraft: A short-cut method and analysis

The air-cycle refrigeration system is widely used in commercial and military aircraft, and its efficiency greatly affects aircraft performance. Nowadays, this system requires a more efficient design and optimization method. In this paper, a short-cut optimization method with high efficiency and effectiveness is introduced for both conventional and electric air-cycle refrigeration systems. Based on the system characteristics, a four-layer parameter matching algorithm is designed which avoids computational difficulty caused by simultaneous equations. Fuel penalty is chosen as the objective function of optimization; design variables are reduced based on sensitivity analysis to improve optimization efficiency. The results show that the 3-variable optimization of the conventional air-cycle refrigeration system can obtain almost the same results as the traditional 6-variable optimization in that these two optimizations can both significantly reduce the fuel penalty. However, the computer running time of the 3-variable optimization is much shorter than that of the 6-variable optimization. The optimal fuel penalty of the electric air-cycle refrigeration system is lower than that of the conventional one. This study can provide reference for optimizing the air-cycle refrigeration system of aircraft.     

Visual inspection of aircraft skin: Automated pixel-level defect detection by instance segmentation

Skin defect inspection is one of the most significant tasks in the conventional process of aircraft inspection. This paper proposes a vision-based method of pixel-level defect detection, which is based on the Mask Scoring R-CNN. First, an attention mechanism and a feature fusion module are introduced, to improve feature representation. Second, a new classifier head—consisting of four convolutional layers and a fully connected layer—is proposed, to reduce the influence of information around the area of the defect. Third, to evaluate the proposed method, a dataset of aircraft skin defects was constructed, containing 276 images with a resolution of 960 × 720 pixels. Experimental results show that the proposed classifier head improves the detection and segmentation accuracy, for aircraft skin defect inspection, more effectively than the attention mechanism and feature fusion module. Compared with the Mask R-CNN and Mask Scoring R-CNN, the proposed method increased the segmentation precision by approximately 21% and 19.59%, respectively. These results demonstrate that the proposed method performs favorably against the other two methods of pixel-level aircraft skin defect detection.     

Exploration and implementation of commonality valuation method in commercial aircraft family design

Commercial aircraft family design can reduce development costs, shorten development cycles, and expand the market coverage of aircraft. Commercial aircraft family development has become one of the most important features of modern aircraft design. This paper explores the effects of commonality on different aircraft models in a commercial aircraft family. The existing product commonality indexes are summarized and their limitations in the application to aircraft design are discussed. Then a new component commonality index is proposed based on the component decomposition structure. A model for calculating the aircraft program value is established,which considers development costs, manufacturing costs, sale price, operation costs and residual costs. The effects of aircraft commonality on time and economic costs of both development and manufacturing, and on sale price, are analyzed and quantified. The commonality evaluation strategy is obtained, which features comprehensive consideration of the aircraft program value and time costs. The break-even analysis of aircraft is proceeded on the basis of costs and price data. By using a real option method, the strategy considers the uncertainty of the aircraft program and the flexibility of the manufacturer. This strategy proves to be rational and applicable to aircraft design based on the calculation of three examples and the analysis of parameter sensitivity.     

基于VMD的自适应复合多尺度模糊熵及其在滚动轴承故障诊断中的应用

提出了一种基于自适应多尺度模糊熵、ILS（迭代拉普拉斯得分）特征选择和粒子群优化支持向量机(PSO-SVM)的滚动轴承故障诊断方法。该方法采用变分模态分解对振动信号进行分解和重构，并计算重构信号的复合多尺度模糊熵；同时采用迭代拉普拉斯得分选择敏感故障特征，并将特征选择结果输入到基于粒子群优化支持向量机的多故障分类器进行识别。将提出的方法应用于滚动轴承试验数据分析。结果表明:该方法对试验数据的故障识别率为100%。并将基于ILS特征选择方法与基于SFS（sequential forward selection）特征选择进行了对比，表明基于SFS特征选择的最高识别率为92.86%，而基于ILS特征选择的故障识别率达到100%。      

一种着陆视觉导航P3P问题的解法

P3P问题是机器视觉领域的经典问题,其多解的排除与唯一解的确定是研究热点。针对飞行器着陆过程中机载视觉设备跑道成像的特点,提出了一种着陆视觉导航P3P问题唯一解的求解方法。该方法首先通过机场跑道的3条边线计算相对姿态,再根据直线方程求解相对位置,最终完成飞行器与跑道之间6个自由度参数的唯一确定。     

A mask R-CNN based method for inspecting cable brackets in aircraft

In the aviation industry, cable bracket is one of the most common parts. The traditional assembly state inspection method of cable bracket is to manually compare by viewing 3D models. The purpose of this paper is to address the problem of inefficiency of traditional inspection method. In order to solve the problem that machine learning algorithm requires large dataset and manually labeling of dataset is a laborious and time-consuming task, a simulation platform is developed to automatically generate synthetic realistic brackets images with pixel-level annotations based on 3D digital mock-up. In order to obtain accurate shapes of brackets from 2D image, a brackets recognizer based on Mask R-CNN is trained. In addition, a semi-automatic cable bracket inspection method is proposed. With this method, the inspector can easily obtain the inspection result only by taking a picture with a portable device, such as augmented reality (AR) glasses. The inspection task will be automatically executed via bracket recognition and matching. The experimental result shows that the proposed method for automatically labeling dataset is valid and the proposed cable bracket inspection method can effectively inspect cable bracket in the aircraft. Finally, a prototype system based on client-server framework has been developed for validation purpose.     

Exploring mission planning method for a team of carrier aircraft launching

High-level efficiency and safety are of great significance for improving the fighting capability of an aircraft carrier. One way to enhance efficiency and safety level is to organize the carrier aircraft into combat effectively. This paper studies the mission planning problem for a team of carrier aircraft launching, and a novel distributed mission planning architecture is proposed. The architecture is hierarchical and is comprised of four levels, namely, the input level, the coordination level,the path planning level and the execution level. Realistic constraints in each level of the distributed architecture, such as the vortex flow effect, the crowd effect and the motion of aircraft, are considered in the model. To solve this problem, a distributed path planning algorithm based on the asynchronous planning strategy is developed. The proposed Mission Planning Approach for Carrier Aircraft Launching(MPACAL) is validated using the setups of the Nimitz-class aircraft carrier.Compared to the isolated planning architecture and the centralized planning architecture, the proposed distributed planning architecture has advantages in coordinating the launch tasks not only belonging to the same catapult but also when all different catapults are considered. The proposed MPACAL provides a modeling method for the flight deck operation on aircraft carrier.     

A multi-agent based intelligent configuration method for aircraft fleet maintenance personnel

A multi-agent based fleet maintenance personnel configuration method is proposed to solve the mission oriented aircraft fleet maintenance personnel configuration problem. The mainte- nance process of an aircraft fleet is analyzed first. In the process each aircraft contains multiple parts, and different parts are repaired by personnel with different majors and levels. The factors and their relationship involved in the process of maintenance are analyzed and discussed. Then the whole maintenance process is described as a 3-layer multi-agent system （MAS） model. A com- munication and reasoning strategy among the agents is put forward. A fleet maintenance personnel configuration algorithm is proposed based on contract net protocol （CNP）. Finally, a fleet of 10 aircraft is studied for verification purposes. A mission type with 3 waves of continuous dispatch is imaged. Compared with the traditional methods that can just provide configuration results, the proposed method can provide optimal maintenance strategies as well.     

基于合作目标和视觉的无人飞行器全天候自动着陆导引关键技术

 GPS受他国控制和易受干扰对基于该导航系统的无人飞行器导航和着陆具有潜在危险,为了使其安全自动着陆,提出通过在着陆跑道(广场或公路)上预设具有受控发射红外光的地面合作目标,实现无人飞行器的视觉全天候自动精确着陆新技术。首先研究得到切实可行的工作过程;然后研制了合作目标,通过理论分析和实验得出,无论能见度高低,8~12 μm中远红外视觉系统探测到的合作目标图像质量远优于可见光视觉系统,研究得到合作目标和背景的温差在170~200 ℃时,成像效果最好。在识别研究中发现,基于传统的不变矩算法对合作目标的识别可靠性稍差,为了进一步准确地识别合作目标,又提出了基于方向链码的合作目标识别算法,该方法的耗时为不变距的96%,但是识别的可靠性比前者有显著提高。     

复杂结构件数控编程加工特征用户自定义方法

加工特征是实现复杂结构件高效、高质量数控编程的有效手段,但是同一类加工特征只是几何形状和加工工艺相似,并不完全相同。如何适应不同的企业资源与工艺水平、不同类型的复杂结构件进行加工特征定义是基于加工特征进行自动数控编程的一个难题。针对以上难题,本文提出了一种复杂结构件数控编程加工特征用户自定义方法,基于全息属性面边图表达加工特征几何信息,给出了具有一定柔性的加工特征几何信息定义方法,基于语义与规则建立加工特征工艺信息及其与几何信息之间的关联关系,实现了由用户根据企业的制造资源、零件结构和工艺人员的编程习惯等因素自定义加工特征。根据本文提出的方法开发了飞机复杂结构件加工特征用户自定义及自动编程系统,已成功应用于国内某大型航空制造企业的飞机结构件数控编程,经过多项飞机结构件测试,本文提出的方法特征识别正确率平均达到97%。     

Optimum alternate material selection methodology for an aircraft skin

Weight penalty has been a challenge for design engineers of aerospace vehicles. Today’s high-efficiency combat aircraft undergoes intense stress and strain during flying missions, which require stronger and stiffer materials to retain structural integrity. Though metallic materials have been successfully used for the construction of aircraft structures and components, metals still have a low strength-to-weight ratio. This paper aims to develop an alternate optimised material selection methodolog...     

An optimization model of parameter matching for aircraft catapult launch

To efficiently and fully utilize aircraft carrier resources, an optimization model is presented to deal with parameter matching between aircraft and carrier in the process of aircraft catapult launch. Based on carrier aircraft longitudinal dynamic equations and theorem of kinetic energy in catapult launch course, the work characteristics of different forces are learned and a theory model of parameter matching is deduced. In view of the uncertainty of the model parameters of the theory model and the low matching accuracy of the approximate model, an optimization model of parameter matching is introduced in line with the structure of theory model and the approximate model and is generated by the proposed immune genetic algorithm. Compared with the original genetic algorithm and immune algorithm, the proposed algorithm has better calculation accuracy and convergence. The calculation results show that the optimization model occupies certain application value of engineering estimation from the comparison with the relevant literature data and has higher precision than the approximate models. The validity of the proposed approach is verified with numerical case study on a carrier based aircraft.     

飞机钣金零件弯边自动展开系统

由于飞机钣金件的复杂性,普通钣金展开软件不适合该类弯边零件的展开.本文分析了飞机钣金零件独有的特征,研究开发了基于CATIA环境下的飞机钣金零件的弯边自动展开系统,提出了一套特有的法向截面展开方法和下陷处理方法,并以实例说明零件的展开过程.     

New criterion for aircraft susceptibility to infrared guided missiles

This paper assesses aircraft susceptibility from the first principles, with respect to the threat posed by passively guided infrared homing missiles; with an objective of gaining insight into the comprehensiveness of the relationship between aircraft susceptibility and aircraft infrared signature level. The conventional criterion of aircraft susceptibility assessment based on its lock-on envelop is found to be inadequate, and a new criterion termed here as the Lethal Envelop is presented. The proposed susceptibility assessment criterion is more relevant for coming generation of infrared-guided missiles, because of advancements in the infrared detection technology. A threshold infrared signature level is also proposed as benchmark to be satisfied by all infrared signature suppression systems; if aircraft susceptibility to infrared guided missiles is to be reduced. This analysis is vital for gauging the effectiveness of infrared signature suppression systems. A typical air-to-air combat situation is simulated, and the results that lead to aircraft susceptibility assessment are obtained from this model, which illustrates the comprehensiveness of the redefined aircraft susceptibility assessment approach.     

Reduction rules-based search algorithm for opportunistic replacement strategy of multiple life-limited parts

The opportunistic replacement of multiple Life-Limited Parts(LLPs) is a problem widely existing in industry.The replacement strategy of LLPs has a great impact on the total maintenance cost to a lot of equipment.This article focuses on finding a quick and effective algorithm for this problem.To improve the algorithm efficiency, six reduction rules are suggested from the perspectives of solution feasibility, determination of the replacement of LLPs, determination of the maintenance occasion and solution optimality.Based on these six reduction rules, a search algorithm is proposed.This search algorithm can identify one or several optimal solutions.A numerical experiment shows that these six reduction rules are effective, and the time consumed by the algorithm is less than 38 s if the total life of equipment is shorter than 55000 and the number of LLPs is less than11.A specific case shows that the algorithm can obtain optimal solutions which are much better than the result of the traditional method in 10 s, and it can provide support for determining tobe-replaced LLPs when determining the maintenance workscope of an aircraft engine.Therefore,the algorithm is applicable to engineering applications concerning opportunistic replacement of multiple LLPs in aircraft engines.     

Exploring 2D projection and 3D spatial information for aircraft 6D pose

The 6D pose estimation is important for the safe take-off and landing of the aircraft using a single RGB image. Due to the large scene and large depth, the exiting pose estimation methods have unstratified performance on the accuracy. To achieve precise 6D pose estimation of the aircraft, an end-to-end method using an RGB image is proposed. In the proposed method, the 2D and 3D information of the keypoints of the aircraft is used as the intermediate supervision, and 6D pose information of the aircraft in this intermediate information will be explored. Specifically, an off-the-shelf object detector is utilized to detect the Region of the Interest (RoI) of the aircraft to eliminate background distractions. The 2D projection and 3D spatial information of the pre-designed keypoints of the aircraft is predicted by the keypoint coordinate estimator (KpNet). The proposed method is trained in an end-to-end fashion. In addition, to deal with the lack of the related datasets, this paper builds the Aircraft 6D Pose dataset to train and test, which captures the take-off and landing process of three types of aircraft from 11 views. Compared with the latest Wide-Depth-Range method on this dataset, our proposed method improves the average 3D distance of model points metric (ADD) and 5° and 5 m metric by 86.8% and 30.1%, respectively. Furthermore, the proposed method gets 9.30 ms, 61.0% faster than YOLO6D with 23.86 ms.     

A method for aircraft magnetic interference compensation based on small signal model and LMS algorithm

Aeromagnetic interference could not be compensated effectively if the precision of parameters which are solved by the aircraft magnetic field model is low. In order to improve the compensation effect under this condition, a method based on small signal model and least mean square（LMS） algorithm is proposed. According to the method, the initial values of adaptive filter＇s weight vector are calculated with the solved model parameters through small signal model at first,then the small amount of direction cosine and its derivative are set as the input of the filter, and the small amount of the interference is set as the filter＇s expected vector. After that, the aircraft magnetic interference is compensated by LMS algorithm. Finally, the method is verified by simulation and experiment. The result shows that the compensation effect can be improved obviously by the LMS algorithm when original solved parameters have low precision. The method can further improve the compensation effect even if the solved parameters have high precision.     

飞机能量机动性及其计算

首先介绍了能量机动性产生的背景和发展。然后给出了能量机动性的计算方法，还介绍了Ｅ－Ｍ图和全局能量机动性图的绘制方法，以及如何用它们来衡量战斗机空战性能，并以Ｆ－１６飞机和ＭＩＧ－２９飞机为例，绘制了Ｅ－Ｍ图及全局能量机动性图。这一研究为国内新一代战斗机设计的评估提供了一种理论研究方法和计算手段。     

基于DELMIA的飞机三维装配工艺设计与仿真

针对我国航空制造业当前装配工艺规划与设计的现状,开展了基于DELMIA进行飞机三维装配工艺设计与仿真方法的研究,对三维装配工艺设计与仿真的关键技术进行了重点分析,包括三维工艺组件划分、装配生产线布局规划、基于知识的装配工艺规划,以及装配仿真中的装配干涉检查、人机工效仿真,并通过某型飞机机翼装配对三维工艺设计与仿真进行了应用验证。     

飞机产品客户化浅析

民用飞机是特殊商品,不同航空公司以及同一航空公司的不同发展阶段,由于其产品经营理念的差别,几乎每架飞机都是与众不同的,因此飞机产品客户化是航空公司和飞机制造商共同关注的话题。空客公司的民用系列飞机获得了世界的认可,其客户选型工作可以提供很好的参考。通过研究分析空客公司的客户选型相关工作,为我国大型客机客户化设计积累必要的技术储备和参考借鉴,并为我国大型客机产品客户化提出了研究方向。