3D multipath planning for UAV based on network graph

According to the characteristic and the requirement of multipath planning,a new multipath planning method is proposed based on network.This method includes two steps:the construction of network and multipath searching.The construction of network proceeds in three phases:the skeleton extraction of the configuration space,the judgment of the cross points in the skeleton and how to link the cross points to form a network.Multipath searching makes use of the network and iterative penalty method (IPM) to plan multi-paths,and adjusts the planar paths to satisfy the requirement of maneuverability of unmanned aerial vehicle (UAV).In addition,a new height planning method is proposed to deal with the height planning of 3D route.The proposed algorithm can find multiple paths automatically according to distribution of terrain and threat areas with high efficiency.The height planning can make 3D route following the terrain.The simulation experiment illustrates the feasibility of the proposed method.     

Graphic theory on interval stability of networked control systems

A new method on the interval stability of networked control systems （NCSs） with random delay and data packet dropout is studied. Combining interval systems and NCSs, a graphic condition on judging interval stability is presented in terms of the weighted diagraph theory in graph theory. Furthermore, utilizing the graph-theoretic algorithm, the delay-depended controller gains are obtained. Aiming at the same delay and data packed dropout, several controller gains are obtained, simultaneously. The example and simulation illustrate the effectiveness of the proposed method.     

Multi-dimensional scattering properties diagnosis system of scale aircraft model in an anechoic chamber

Aiming at the concept of ＂diagnosis＂, a simple and effective broadband radar cross section （RCS） measurement system is constructed, and some multi-dimensional scattering properties diagnosis techniques are presented based on the system. Firstly, a stepped-frequency signal is employed to achieve high range resolution, combining with a variety of signal processing tech- niques. Secondly, cross-range resolution is gained with a rotating table, and the high-resolution two-dimensional （2-D） imaging of the scale model is obtained by the microwave imaging theory. Finally, two receiving antennas with a small distance in altitude are used, and the three-dimensional （3-D） height distribution of scattering points on the scale model is extracted from the phase of images. Some typical bodies and a scale aircraft model are diagnosed in an anechoic chamber. The experimental results show that, after scaling with a metal sphere, the accurate one- dimensional （l-D） RCS pattern of the model is obtained, and it has a large dynamic range. When the bandwidth of the transmitting signal is 4 GHz, the resolution of the 2-D image can reach to 0.037 5 m. The 3-D height distribution of scattering points is given by interferometric measurement. This paper provides a feasible way to obtain high-precision scattering properties parameters of the scale aircraft model in a conventional rectangular anechoic chamber.     

准坐标系下的弹性飞行器飞行动力学建模

结合有限元思想和拉格朗日方程推导了准坐标系下的弹性飞行器飞行动力学模型,与通常采用的平均轴系建模方法相比,该方法克服了变量难在相同坐标系下表示等缺点,而且该模型包含了自由度之间所有的耦合,能够更充分的反映刚性自由度与弹性自由度间的交叉耦合特性,更全面的从本质上体现飞行器结构动力学、空气动力学以及飞行动力学这种多学科之间相互影响的非线性飞行动力学特性。该动力学模型可用于弹性飞行器非线性稳定性分析、弹性飞行器飞行动力学与控制理论分析等。

Abstract：

As the frequency separation between the rigid body modes and the structural dynamics becomes tighter, the traditional aircraft flight mechanics treatment, there is, the rigid body approximation, may be not efficient. A complete coupled equation of motion for fully flexible aircrafts were derived, without any constraint relationship, which was done by employing Lagrange’s equations and the finite element method in terms of quasi-coordinates. This model includes automatically all six rigid-body degrees of freedom and elastic deformations, as well as the gravity, propulsion, aerodynamics, and control forces, in addition to forces of an external nature, such as gusts. Different from the modeling method based on ＂mean axes＂ coordinate system, the seamless integration was achieved by using the same reference frame and the same variables to describe the aircraft motions and the force acting on it, including the aerodynamic forces. The formulation is modular in nature, in the sense that the structural model, the aerodynamic theory, and the controls method can be replaced by any other ones to better suit different types of aircraft, provided certain criteria are satisfied.     

Adaptive learning algorithm based on mixture Gaussian background

The key problem of the adaptive mixture background model is that the parameters can adaptively change according to the input data. To address the problem, a new method is proposed. Firstly, the recursive equations are inferred based on the maximum likelihood rule. Secondly, the forgetting factor and learning rate factor are redefined, and their still more general formulations are obtained by analyzing their practical functions. Lastly, the convergence of the proposed algorithm is proved to enable the estimation converge to a local maximum of the data likelihood function according to the stochastic approximation theory. The experiments show that the proposed learning algorithm excels the formers both in converging rate and accuracy.     

Cooperative localization against GPS signal loss in multiple UAVs flight

Based on multiple unmanned aerial vehicles(UAVs) flight at a constant altitude,a fault-tolerant cooperative localization algorithm against global positioning system(GPS) signal loss due to GPS receiver malfunction is proposed.Contrast to the traditional means with single UAV,the proposed method is based on the use of inter-UAV relative range measurements against GPS signal loss and more suitable for the small-size and low-cost UAV applications.Firstly,for re-localizing an UAV with a malfunction in its GPS receiver,an algorithm which makes use of any other three healthy UAVs in the cooperative flight as the reference points for re-localization is proposed.Secondly,by using the relative ranges from the faulty UAV to the other three UAVs,its horizontal location can be determined after the GPS signal is lost.In order to improve an accuracy of the localization,a Kalman filter is further exploited to provide the estimated location of the UAV with the GPS signal loss.The Kalman filter calculates the variance of observations in terms of horizontal dilution of positioning(HDOP) automatically.Then,during each discrete computing time step,the best reference points are selected adaptively by minimizing the HDOP.Finally,two simulation examples in Matlab/Simulink environment with five UAVs in cooperative flight are shown to evaluate the effectiveness of the proposed method.     

基于混沌差分进化算法的飞机等效系统拟配研究

提出了基于Tent映射的混沌差分进化算法。以某飞机纵向短周期系统为例,首次研究了基于混沌差分进化算法的飞机等效系统的拟配,克服了一些传统的拟配算法存在的一些缺点。仿真结果表明,基于混沌差分进化算法拟配得到的等效系统满足等效系统拟配的各项要求和一级飞行品质的要求,取得了更好的拟配效果。证明该算法在飞机等效系统拟配中的有效性和高效性。

Abstract：

Chaotic differential evolution algorithm based on Tent map was introduced. Taking aircraft longitudinal short period system as an example,the analog-matching of the aircraft longitudinal equivalent system based on chaotic differential evolution algorithm was studied firstly and overcome the disadvantages of the conventional algorithms in the analog-matching of equivalent system. The simulation results show that the equivalent system by chaotic differential evolution algorithm is satisfied the various requirements in the analog-matching of equivalent system and the requirement of level 1 flight qualities,and has obtained better analog-matching results. The usefulness and high effectiveness of the chaotic differential evolution algorithm in the analog-matching of aircraft equivalent system is proved.     

Airborne sparse flight array SAR 3D imaging based on compressed sensing in frequency domain

In airborne array synthetic aperture radar(SAR), the three-dimensional(3D) imaging performance and cross-track resolution depends on the length of the equivalent array. In this paper, Barker sequence criterion is used for sparse flight sampling of airborne array SAR, in order to obtain high cross-track resolution in as few times of flights as possible. Under each flight, the imaging algorithm of back projection(BP) and the data extraction method based on modified uniformly redundant arrays(MURAs...     

Carbon Emission Measurement and the Decoupling Effect Under the “Double Carbon” Goal in Xi'an,China

Cities generate more than 60% of carbon emissions and are the main battleground for achieving the target. However, there is no unified and standardized measurement methods of carbon emissions in cities. In this paper, we took Xi’an as an example and started by measuring carbon emissions with the new standards. Then, the decoupling of economic development from carbon emissions was studied according to the Tapio decoupling theory. Based on the generalized Divisia index method,the decoupling effort...     

A Parallel Algorithm for Corner Detection on Object Contour

; A new parallel algorithm for corner detection on object contour is presented in the paper. In this algorithm whenever a point (pixel) is scanned, the k direction codes between the two sides of the point, which is on the edge of an object, are obtained by k-step forward and backward boundary tracking. A comer is determined by the sum of the difference between the two weighted code chains. Note that the whole chain code sequence or boundary of an object is not necessary to be extracted at all in this algorithm, and the corners are obtained immediately once the image is scanned, furthermore, what humans perceive as corners can be detected and localized by this algorithm.     

基于非线性映射分析的期货逼仓风险判定模型及其应用

选用资金、价格、持仓量等三类指标来反映期货交易中的逼仓风险,采用非线性映射分析将交易中存在逼仓风险的交易日分离成独立的点群.根据离差极小、最大欧氏距离等原理提出逼仓风险阈值计算方法及逼仓风险判定方法.其特点一是运用非线性映射分析等原理给出了逼仓风险阈值的求解方法及风险判定方法,使逼仓风险在酝酿初期就可被及时、准确地判定出来,为期货交易逼仓风险管理提供了预警功能.二是通过与系统聚类结果的对比,验证了非线性映射分析方法的科学性和有效性.三是以豆粕s0409的244个有效样本作为总样本,举例说明了逼仓阈值的求解及风险判定过程.并随机抽取了该合约中的30个样本进行检验,检验结果表明该判别方法的精度高达93.33%.     

基于光电融合的目标三维结构反演

针对同传感器视角下的空天目标光电特征融合问题, 提出一种综合利用散射中心参数及轮廓角点特征的目标三维结构反演方法。首先, 基于正交匹配追踪(orthogonal matching pursuit, OMP)算法估计出序列雷达图像中的二维散射中心特征, 并利用Freeman链码提取连续可见光图像的角点特征。然后, 基于图论思想分别对雷达及可见光图像中的二维特征点进行关联。最后, 通过特征点三维重构来实现散射中心特征与光学角点特征之间的融合, 从而反演出较单源特征更为丰富准确的目标结构信息。仿真试验结果验证了所提方法的有效性。     

基于DirectX的微型飞行器飞行仿真系统

介绍了一种运行在PC/Windows平台上的微型飞行器飞行实时仿真系统,该系统在VC 6.0编程环境下用DirectX开发。在飞行动力学和运动学仿真中,采用了六自由度全量非线性方程,以微型飞行器的风洞吹风实验数据为依据,考虑了螺旋桨的气动扭矩、陀螺力矩和尾流对微型飞行器的影响,精确地反映了微型飞行器的实际运动特性。应用此飞行仿真软件,除可以进行全面的飞行动力学分析外,还应用于微型飞行器的设计、试飞、侦察评估等方面。     

非定常大气扰动下的MAV自主飞行智能控制研究

针对在非定常大气扰动作用下,微型飞行器MAV姿态稳定控制与导航都不同于常规的问题。研究了MAV飞行中大气扰动类型特征,建立了完整的非定常大气扰动工程化模型体系。在此基础上,提出了一种融合专家技术与模糊技术的MAV自主飞行智能控制,并建立了一个Lyapunov能量函数来分析MAV自主飞行系统稳定性。飞行仿真与试飞结果表明,MAV自主飞行系统在全局范围内具有渐进稳定性。     

基于单目视觉的微型飞行器移动目标定位方法

针对目标在地形高度未知环境中移动的情况,给出一种利用微型飞行器机载单目摄像机进行目标定位的方法。首先,借助光流直方图从当前图像帧中提取出移动目标局部区域内的背景特征点|然后,结合机载微机电系统(micro electro mechanical system, MEMS)/ 全球定位系统(global positioning system, GPS)传感器测量的飞行器位姿和空间平面点成像的单应变换关系,在期望值最大化算法中将背景特征点分类为辅助平面点和非辅助平面点,并估计辅助平面到摄像机光心的距离参数和法矢量参数,从而确定移动目标所处辅助平面的空间平面方程|最后,联立求解目标视线方程和辅助平面方程获得交点坐标,转换到惯性系下完成移动目标的地理定位。实验结果表明,当微型飞行器飞行高度为100 m时,操作人员单次点击移动目标的定位误差在15 m以内。     

微型涵道飞行器的自适应逆控制方法

微型涵道飞行器可以悬停、垂直起降和前飞,且安全性高、结构紧凑、噪声低。但是,微型涵道飞行器由于大飞行包线、特殊气动布局、低速度、小尺寸和复杂飞行环境,所以具有明显的非定常和非线性飞行力学特性。针对这一问题,研究了应用动态逆控制律的新方法--神经网络自适应逆。采用动态逆控制器、神经网络补偿器、比例微分(proportion-derivative,PD)补偿器和伪控制补偿器构建了微型涵道飞行器飞行控制系统。仿真结果表明,相比动态逆 比例积分微分(proportion-integral-derivative,PID控制系统,本文设计的自适应逆控制系统具有更强的稳定性和鲁棒性。     

基于人机合作的有人/无人机编队队形变换策略

队形变换是有人/无人机(manned/unmanned aerial vehicle, MAV/UAV)编队飞行的关键技术,为提高编队队形变换效率并减轻飞行员操纵压力,设计了基于人机合作的MAV/UAV编队队形变换策略。首先设计了MAV/UAV编队控制系统,然后在UAV运动学模型基础上设计了一种以路径跟踪为主,速度调节为辅的MAV/UAV编队队形变换策略。通过将水平转弯机动与虚拟力相结合,并考虑实际情况中编队内碰撞问题,设计了一种改进虚拟力路径跟踪方法;根据MAV与各UAV之间的路径差,设计各UAV速度控制律,使得MAV与各UAV速度与航向角一致,从而实现编队队形变换。仿真结果验证了所提方法的有效性和实用性。     

基于角点特征的KLT跟踪全景图像拼接算法

虚拟现实技术在航空航天、机器人遥操作和生物医学等领域得到了广泛应用，已成为研究问题的一种重要手段，全景图像的拼接技术则是其中一个非常重要的环节。通过SUSAN检测算子提取图像特征角点，利用快速RANSAC算法来实现图像的初配准．然后把检测到特征角点作为图像中的运动目标，利用KLT跟踪算法，确定各特征角点的精确位置，从而得到图像之间精确的单应性变换矩阵。在图像融合过程中，提出了消除图像拼接过程中“鬼影”的办法。实验结果表明，该算法能够大大提高图像配准精确度，并具有较好的鲁棒性。     

基于CSS角点提取的红外与可见光图像匹配算法

针对红外与可见光图像中特征点匹配的难题,提出了一种基于曲率尺度空间（curvature scale space,CSS)角点提取的特征点匹配算法。首先采用基于曲率尺度空间的角点检测算法进行特征点提取;其次利用三维二次函数剔除低对比度的特征点;然后以特征点所在曲线的法线作为主方向,避免了图像的旋转代价;再通过计算构建特征点邻域的梯度方向在［0,π)范围的分布直方图,计算其统计特征并构造一个64维的特征点描述符,并进行归一化;最后采用最近邻算法实现直线匹配。实验结果表明,该算法能够有效地实现对红外与可见光图像特征点的精确匹配。     

无人机自主着陆地标实时检测方法

在基于计算机视觉的无人机自主着陆过程中,地标的设计与检测是关键问题。提出了一种快速轮廓角点检测算法,并设计了一种新型嵌套三角形图案作为无人机自主着陆地标。首先,利用Suzuki-Abe算法提取的背景及目标的整体轮廓信息,进行目标嵌套轮廓提取;其次,通过改进Douglas-Peucker拟合算法来检测轮廓角点。由于优化了角点个数及最远距离两点的寻找方法,在很大程度上减少了计算时间且降低了复杂度。实验结果表明,在距离地标较远、地标部分信息缺失的情况下,该算法准确快速,适合于无人机自主着陆过程位置实时检测。