Automatic algorithm for inverse synthetic aperture radar images recognition and classification

The authors propose an algorithm for automatic aircraft categories that is models classification from inverse synthetic aperture radar (ISAR) images that use pulse reflection shape and Doppler shifts of parts of aircraft that are in any maneuver that introduces rotation to the target. The authors artificially generated five different categories of ISAR aircraft using computer simulations and tested these simulated ISAR aircraft images of the airplanes defined by size and shape that are flying in a prescribed holding pattern. The authors investigate in what parts of the holding pattern the ISAR reflections provide information that makes it possible to identify to which of the five categories an aircraft in the holding pattern belongs. The obtained results show that it is possible in most parts of the holding pattern to successfully classify the various aircraft targets.     

飞机结构健康监测系统数据处理及在线应用

阐述了飞机结构健康监测的概念和基本组成部分,从监测结构和监测量方面梳理了常见的监测对象;评述了近期结构健康监测数据处理的典型研究成果,主要包括数据采集和预处理、数据分析两个方面,可以看到智能计算的思想和方法越来越多地应用在其中;展望了飞机结构健康监测未来走向大范围在线工程应用的趋势,有针对性地提出了三个要点,分别是机载化在线监控系统硬件的研发、算法的开发和行业的标准化,然后梳理了飞机结构健康监测传感器技术的近期研究案例,并介绍了新兴算法应用于在线监测系统中的案例,为进一步推动飞机结构健康监测系统研究提供参考与借鉴。     

A Novel Edge Computing Based Area Navigation Scheme

The area navigation system, discussed in this paper, is composed of ground responders and a navigation terminal and can position a high-velocity aircraft and measure its velocity. This navigation system is silent at ordinary times. It sends out a request signal when positioning is required for an aircraft, and then the ground responders send a signal for resolving the aircraft. Combining the direct sequence spread spectrum and frequency hopping, the concealed communication mode is used in the whole communication process, with short communication pulses as much as possible, so the system has strong concealment and anti-interference characteristics. As the transmission delay is apparent in the response communication mode, there is a big error where the common navigation algorithm is used for the positioning and velocity measurement of a high-velocity aircraft. In this paper, a new algorithm is proposed, which can eliminate the influence of response communication delay on the positioning of a high-velocity moving target to realize the precise positioning and velocity measurement of a high-velocity aircraft.     

一种用于飞机易损性分析的几何描述方法

在进行飞机易损性分析时，需要计算飞机及各部件在垂直于来袭方向的投影面积。由于机翼、机身及其它部件在不同的来袭方向上存在不同程度的遮挡，从而使得投影面积的计算繁琐复杂。笔者介绍了利用B样条方法和C＋＋面向对象语言开发的飞机武器几何描述系统，着重论述了系统的结构、功能和形体表示的数据结构，提出了一种求取具有多重遮挡关系的复杂几何形体在任意方向上投影面积的高效算法。通过实例应用表明该算法稳定可靠，且精度高，所建系统具有较好的实用价值。     

基于BDPCA聚类算法的航空发动机故障数据标记

航空发动机作为飞行器的动力核心对飞行器的安全飞行有着举足轻重的作用,保证航空发动机的平稳运行对飞行安全有着重大意义。在基于有监督学习的航空发动机故障诊断技术不断取得进展的同时,如何将平时获取的大量未标记数据转换为能够用来训练故障诊断模型的带标记数据,成为了制约行业发展的一大瓶颈。针对这一问题引入了基于无监督学习的DPCA算法,用以实现对未标记数据集的准确分类与标记,并针对DPCA算法在局部密度计算与簇类别数选择方面的缺陷进行了优化:针对原始DPCA算法应用标准高斯核计算局部密度易造成误识别的状况,引入共享邻域算法对局部密度的计算方法进行优化;针对原始DPCA算法需要人工研判确定簇类别数易造成的误识别状况,引入BIC选择准则对簇类别数的选择方法进行优化;提出了原始DPCA算法与共享邻域算法以及BIC选择准则相结合的BDPCA算法。最后应用航空发动机转子故障数据对BDPCA算法进行了性能验证并取得了良好的结果,证实了BDPCA算法在航空发动机气路故障诊断领域有较高的实用价值。     

FATIGUE LIFE UNDER RANDOM LOAD HISTORY DERIVED FROM EXCEEDANCE CURVES USING DIFFERENT ALGORITHMS

Low cycle fatigue life and crack growth rates were analytically estimated for random load sequences, generated from three combat aircraft load exceedance curves using different algorithms, including simulated rainflow cycle count, extreme-to-extreme excursions, upper to lower bound excursions and unrestricted peak-trough excursions. Also, the response of a fatigue meter to a random load sequence was simulated. Fatigue damage for the different load histories was computed using material constants for an Al-Cu alloy. Computed fatigue damage was relatively insensitive to the algorithm used for load sequence generation from combat aircraft load exceedance curves. Fatigue meter data based damage estimates were, however, sometimes unconservative.     

3D Trajectory Planning of Positioning Error Correction Based on PSO-A* Algorithm

Aiming at the yaw problem caused by inertial navigation system errors accumulation during the navigation of an intelligent aircraft, a three-dimensional trajectory planning method based on the particle swarm optimization-A star (PSO-A*) algorithm is designed. Firstly, an environment model for aircraft error correction is established, and the trajectory is discretized to calculate the positioning error. Next, the positioning error is corrected at many preset trajectory points. The shortest trajectory and the fewest correction times are regarded as optimization goals to improve the heuristic function of A star (A*) algorithm. Finally, the index weights are continuously optimized by the particle swarm optimization algorithm. The optimal trajectory is found by the A* algorithm under the current evaluation index, so the ideal trajectory is planned. The experimental results show that the PSO-A* algorithm can quickly search for ideal trajectories in different environment models, indicating that the algorithm has certain feasibility and adaptability, and verifies the rationality of the proposed trajectory planning model. The PSO-A* algorithm has better convergence accuracy than the A* algorithm, and the search efficiency is significantly better than the grid search A star (GS-A*) algorithm. The PSO-A* algorithm proposed in this paper has certain engineering application value. The researchers will study the realtime and systematic nature of the algorithm.     

Performance improvement of an active vibration absorber subsystem for an aircraft model using a bees algorithm based on multi-objective intelligent optimization

This study develops a mathematical model to investigate the behaviour of adaptable shock absorber dynamics for the six-degree-of-freedom aircraft model in the taxiing phase. The purpose of this research is to design a proportional-integral-derivative technique for control of an active vibration absorber system using a hydraulic nonlinear actuator based on the bees algorithm. This optimization algorithm is inspired by the natural intelligent foraging behaviour of honey bees. The neighbourhood search strategy is used to find better solutions around the previous one. The parameters of the controller are adjusted by minimizing the aircraft’s acceleration and impact force as the multi-objective function. The major advantages of this algorithm over other optimization algorithms are its simplicity, flexibility and robustness. The results of the numerical simulation indicate that the active suspension increases the comfort of the ride for passengers and the fatigue life of the structure. This is achieved by decreasing the impact force, displacement and acceleration significantly.     

机翼屏蔽对航空发动机噪声预测的影响分析

随着对飞机适航噪声的要求更加严格,利用机翼屏蔽效应对航空发动机进行噪声控制已成为一项有效策略与研究方向.基于惠更斯-菲涅尔原理,利用飞机噪声性能(Aircraft Noise and Performance,ANP)数据库计算飞机起飞航迹并在其上建立噪声源,声源位置作为噪声屏蔽计算坐标输入屏蔽效应算法,应用Matlab...     

基于阵列传感器的复合材料结构损伤MUSIC成像方法

提出了一种基于传感器线阵的多重信号分类(Multiple Signal Classification,MUSIC)损伤成像方法用于航空复合材料的损伤监测。该方法采用MUSIC阵列信号处理方法,通过对传感器阵列信号进行协方差特征值分解,在结构上进行方向扫描并构建监测区域的空间谱,从而实现对结构损伤的成像,具有一维传感器阵列易于布置的优点。所提出的方法在变厚度航空复合材料油箱结构上进行了验证,结果表明,该方法能够准确实现航空复合材料结构上的损伤成像,定位误差小于2cm。     

Thermodynamic product retrieval methodology and validation for NAST-I

The National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed (NAST) consists of two passive collocated cross-track scanning instruments, an infrared interferometer (NAST-I) and a microwave radiometer (NAST-M), that fly onboard high-altitude aircraft such as the NASA ER-2 at an altitude near 20 km. NAST-I provides relatively high spectral resolution (0.25-cm(-1)) measurements in the 645-2700-cm(-1) spectral region with moderate spatial resolution (a linear resolution equal to 13% of the aircraft altitude at nadir) cross-track scanning. We report the methodology for retrieval of atmospheric temperature and composition profiles from NAST-I radiance spectra. The profiles were determined by use of a statistical eigenvector regression algorithm and improved, as needed, by use of a nonlinear physical retrieval algorithm. Several field campaigns conducted under varied meteorological conditions have provided the data needed to verify the accuracy of the spectral radiance, the retrieval algorithm, and the scanning capabilities of this instrumentation. Retrieval examples are presented to demonstrate the ability to reveal fine-scale horizontal features with relatively high vertical resolution.     

基于希尔伯特变换的信号解调算法及其在飞机供电特性参数测试系统中的应用

电压调制幅度、频率调制幅度和畸变频谱是对飞机机载电源系统供电特性参数进行测试时与信号调制相关的重要参数。为了更好地测试这些参数,提出了一种基于希尔伯特变换原理的数字解调算法,可以将采集的幅度或频率调制信号进行解调分析;同时,构建了一套飞机供电特性参数测试系统,将解调程序与硬件设备结合,通过程序控制数据采集卡对机载电源信号采样与解调分析;设计了实验对波形发生器产生的调制信号进行采样与解调,验证了该系统具有良好的效果,可以应用于飞机供电特性参数的测试中。     

An automated approach for planning mass tactical airborne operations

This paper develops an automated approach to plan for mass tactical airborne operations. This proposed tool enables the user to properly load aircraft according to the mission and user specifications, so that the minimum amount of time is required to seize all assigned objectives. The methodology is based on a hybrid approach in which the first portion is a mathematical model that provides the optimal manifest under “perfect conditions”. This mathematical model is represented by a transportation network, and can be optimized using a transportation algorithm. The optimum solution from the mathematical model is input to a simulation model that introduces the inherent variability induced by wind conditions, drift, aircraft location and speed, and delays between jumper exit times. The simulation returns the expected, best, and worst arrival times to the assigned objectives. This hybrid approach allows a large problem to be solved efficiently with a great deal of time saving.     

A method of determining the dynamic error of optical trajectory measurement stations

The need to take into account the dynamic error of optical trajectory measurement stations in order to increase the precision with which the flight trajectory of aircraft is determined, is evaluated. An algorithm for determining the dynamic error is presented and a calculation of the dynamic error for an optoelectronic station is given.     

Defect Detection in Carbon-Fiber Composites using Lamb-Wave Tomographic Methods

Lamb-wave tomography (LWT) offers a powerful nondestructive technique for the health assessment of large structures as their propagation properties depend on the thickness and the mechanical properties of the material. Development of a fast and accurate algorithm for defect detection is of paramount importance in any structural-health-monitoring (SHM) system. The present study explores the prospects of LWT as a SHM technique with an accent on developing a suitable algorithm for real-time inspection. Projection data is collected by electronically scanning an array of ultrasonic sensors arranged in a modified cross-hole geometry. The data thus collected is investigated to extract energy profile of the traveling waves. Multiplicative algebraic reconstruction technique (MART) algorithms are used as a tool for tomographic reconstruction from a set of multiple independent measurements. The performance of algorithms is evaluated from the point of view of the cost of algorithm, achievable resolution, and accuracy of results. Experimental results show that MART is capable of characterizing defects in thin isotropic and composite plates within a reasonable error band (±26% normalized, ±2.6 RMS) and is suitable for application to LWT of large structures such as aircraft skins.     

Mathematical model and algorithm of toolpath optimisation on aircraft structural parts

An intelligent toolpath (processing sequence) planning for fabricating aircraft structural parts is developed to obtain a minimum-length toolpath while maintaining the required machining time. The problem is first solved in the following ways. Firstly, an abstraction of the machining process is proposed to pick up the feed/retract points of each feature to be machined as the toolpath calculation basis. Secondly, the chaotic simulated annealing method is improved through storing the optimal solution, adding the control condition and selecting each parameter reasonably during the iteration of the algorithm so as to enhance its performance. What’s more, three solution-generating methods are used chaotically to obtain a better result. Lastly, the verification is conducted on four different aircraft structural parts, and the results prove that the proposed algorithm performs very well in terms of toolpath quality and computation time.     

涡桨飞机机体外表面噪声源计算与实验验证

针对某型涡桨飞机在巡航状态下机体表面的主要噪声源（附面层噪声和螺旋桨噪声）分别进行了计算及结果验证。利用VA-One软件开展了机身表面不同位置处附面层噪声数值计算,同时利用半经验公式进行了螺旋桨近场噪声的计算研究。综合考虑两种噪声源的计算结果,与该型涡桨飞机的机体外表面噪声实测结果进行了对比研究。结果表明,仿真和理论计算相结合的计算结果与实测结果吻合较好,验证了算法的正确性。该算法可应用于涡桨飞机机身外表面噪声载荷及舱内噪声预计。     

气动伺服弹性系统结构陷幅滤波器优化设计

为解决飞机气动伺服弹性耦合频率低且随飞机重量构型变化大,使用结构陷幅滤波器改善飞机气动伺服弹性稳定性易于影响飞机操稳特性的问题,建立了一种基于多目标遗传算法的结构陷幅滤波器优化设计方法。以气动伺服弹性系统的弹性模态频响峰值最小作为优化目标,刚体模态频响特性作为设计约束,通过设计罚函数修正个体适应度对陷幅滤波器的频率与阻尼参数进行优化。结果表明:该文方法能够兼顾飞机的气动伺服弹性与刚体运动特性,有利于充分利用高增益控制系统提升飞行性能。     

Vertical profiles of microphysical particle properties derived from inversion with two-dimensional regularization of multiwavelength Raman lidar data: experiment

Inversion with two-dimensional (2-D) regularization is a new methodology that can be used for the retrieval of profiles of microphysical properties, e.g., effective radius and complex refractive index of atmospheric particles from complete (or sections) of profiles of optical particle properties. The optical profiles are acquired with multiwavelength Raman lidar. Previous simulations with synthetic data have shown advantages in terms of retrieval accuracy compared to our so-called classical one-dimensional (1-D) regularization, which is a method mostly used in the European Aerosol Research Lidar Network (EARLINET). The 1-D regularization suffers from flaws such as retrieval accuracy, speed, and ability for error analysis. In this contribution, we test for the first time the performance of the new 2-D regularization algorithm on the basis of experimental data. We measured with lidar an aged biomass-burning plume over West/Central Europe. For comparison, we use particle in situ data taken in the smoke plume during research aircraft flights upwind of the lidar. We find good agreement for effective radius and volume, surface-area, and number concentrations. The retrieved complex refractive index on average is lower than what we find from the in situ observations. Accordingly, the single-scattering albedo that we obtain from the inversion is higher than what we obtain from the aircraft data. In view of the difficult measurement situation, i.e., the large spatial and temporal distances between aircraft and lidar measurements, this test of our new inversion methodology is satisfactory.