Efficient and Effective 4D Trajectory Data Cleansing

As the rapid development of aviation industry and newly emerging crowd-sourcing projects such as Flightradar24 and FlightAware,large amount of air traffic data,particularly four-dimension(4D)trajectory data,have become available for the public.In order to guarantee the accuracy and reliability of results,data cleansing is the first step in analyzing 4D trajectory data,including error identification and mitigation.Data cleansing techniques for the 4D trajectory data are investigated.Back propagation(BP)neural network algorithm is applied to repair errors.Newton interpolation method is used to obtain even-spaced trajectory samples over a uniform distribution of each flight’s 4D trajectory data.Furthermore,a new method is proposed to compress data while maintaining the intrinsic characteristics of the trajectories.Density-based spatial clustering of applications with noise(DBSCAN)is applied to identify remaining outliers of sample points.Experiments are performed on a data set of one-day 4D trajectory data over Europe.The results show that the proposed method can achieve more efficient and effective results than the existing approaches.The work contributes to the first step of data preprocessing and lays foundation for further downstream 4D trajectory analysis.

4D ConflictFree Trajectory Planning for Fixed-Wing UAV

Four-dimensional trajectory based operation(4D-TBO)is believed to enhance the planning and execution of efficient flights,reduce potential conflicts and resolve upcoming tremendous flight demand.Most of the 4D trajectory planning related studies have focused on manned aircraft instead of unmanned aerial vehicles(UAVs).This paper focuses on planning conflict-free 4D trajectories for fixed-wing UAVs before the departure or during the flight planning.A 4D trajectory generation technique based on Tau theory is developed,which can incorporate the time constraints over the waypoint sequence in the flight plan.Then the 4D trajectory is optimized by the particle swarm optimization(PSO)algorithm.Further simulations are performed to demonstrate the effectiveness of the proposed method,which would offer a good chance for integrating UAV into civil airspace in the future.

4D Trajectory Tracking Control for Aircraft Based on Point-to-Point Iterative Learning Control with Current-Cycle Feedback

A point-to-point iterative learning control method with the current-cycle feedback is proposed to enable aircraft to achieve an accurate four-dimensional(4D) trajectory tracking. To this end,the 4D trajectory tracking control problem is formulated into a point-to-point tracking control issue with an external disturbance. Then,the optimal point-to-point iterative learning control law is derived based on the successive projection method. Further,the current-cycle feedback error is added to the control law,so that the tracking error is reduced in both time and iteration domains. Finally,a numerical simulation is carried out using the kinematic model of an unmanned aerial vehicle and 4D trajectory data. Obtained results demonstrate that the proposed method can quickly reduce the trajectory tracking error even in the presence of gust interferences. Compared with the commonly used average velocity method and the velocity correction method,the proposed method makes full use of the past and current running data,and can continuously improve the accuracy of 4D trajectory tracking with the repetitive operation of aircraft between city pairs.

Bio-inspired Collision-free 4D Trajectory Generation for UAVs Using Tau Strategy

Inspired by the general tau theory in animal motion planning, a collision-free four-dimensional （4D） trajectory generation method is presented for multiple Unmanned Aerial Vehicles （UAVs）. This method can generate a group of optimal or near-optimal collision-free 4D trajectories, the position and velocity of which are synchronously planned in accordance with the arrival time. To enlarge the shape adjustment capability of trajectories with zero initial acceleration, a new strategy named intrinsic tau harmonic guidance strategy is proposed on the basis of general tau theory and harmonic motion. In the case of multiple UAVs, the 4D trajectories generated by the new strategy are optimized by the bionic Particle Swarm Optimization （PSO） algorithm. In order to ensure flight safety, the protected airspace zone is used for collision detection, and two collision resolution approaches are applied to resolve the remaining conflicts after global trajectory optimization. Numerous simulation results of the simultaneous arrival missions demonstrate that the proposed method can effectively provide more flyable and safer 4D trajectories than that of the existing methods.

Global 4-D trajectory optimization for spacecraft

Global 4-D trajectory(x,y,z,t)is optimized for a spacecraft,which is launched from the Earth to fly around the Sun,just as star-drift of 1437 asteroids in the solar system.The spacecraft trajectory is controlled by low thrust.The performance index of optimal trajectory is to maximize the rendezvous times with the intermediate asteroids,and also maximize the final mass.This paper provides a combined algorithm of global 4-D trajectory optimization.The algorithm is composed of dynamic programming and two-point-boundary algorithm based on optimal control theory.The best 4-D trajectory is obtained:the spacecraft flies passing 55 asteroids,and rendezvous with(following or passing again)asteroids for 454 days,and finally rendezvous with the asteroid 2005SN25 on the day 60521(MJD),the final mass of the spacecraft is 836.53 kg.

Design of a continuous fiber trajectory for 4D printing of thermally stimulated composite structures

Deformation control of 4D printing has always been challenging.Herein,a design method for the fiber trajectory for 4D printing composite structures with embedded continuous fibers is reported,wherein the designed composite structures can be deformed into many types of deployable surfaces.Deformation of the bilayer composite structure was driven by differences in the coefficients of thermal expansion(CTEs)between the resin substrate and embedded fibers.The bending curvature and direction of the composite structure is controlled by adjusting fiber orientations.According to differential geometry theory,the relationship between the angle of intersecting fiber bundles and curvature of the final shape was obtained.Therefore,arbitrary deployable surfaces,including conical,cylindrical,and tangent surfaces,can be deformed.This design and additive manufacturing strategy allow precise control of the deforming process,greatly extending the potential applications of 4D printing.

A multi-objective multi-memetic algorithm for network-wide conflict-free 4D flight trajectories planning

Under the demand of strategic air traffic flow management and the concept of trajectory based operations（TBO）,the network-wide 4D flight trajectories planning（N4DFTP） problem has been investigated with the purpose of safely and efficiently allocating 4D trajectories（4DTs）（3D position and time） for all the flights in the whole airway network.Considering that the introduction of large-scale 4DTs inevitably increases the problem complexity,an efficient model for strategiclevel conflict management is developed in this paper.Specifically,a bi-objective N4 DFTP problem that aims to minimize both potential conflicts and the trajectory cost is formulated.In consideration of the large-scale,high-complexity,and multi-objective characteristics of the N4DFTP problem,a multi-objective multi-memetic algorithm（MOMMA） that incorporates an evolutionary global search framework together with three problem-specific local search operators is implemented.It is capable of rapidly and effectively allocating 4DTs via rerouting,target time controlling,and flight level changing.Additionally,to balance the ability of exploitation and exploration of the algorithm,a special hybridization scheme is adopted for the integration of local and global search.Empirical studies using real air traffic data in China with different network complexities show that the proposed MOMMA is effective to solve the N4 DFTP problem.The solutions achieved are competitive for elaborate decision support under a TBO environment.

基于数据挖掘的四维飞行轨迹预测模型

为了解决传统的空气动力学模型在预测四维飞行轨迹上误差较大的问题,提出一种基于数据挖掘的预测模型。该模型挖掘历史飞行时间数据,从中找出影响飞行时间的因素,预测出下一次飞行的全程时间,然后从历史位置数据中分析得出飞机在每个采样周期点上的位置,实现完整的四维轨迹预测。仿真试验验证了该模型预测的准确性和可用性。

四维飞行轨迹预测方法的研究

通过对空中交通运输管理中目前常用的轨迹预测算法的研究比较和分析,提出了利用遗传算法的从历史数据中进行函数挖掘的思想。针对四维轨迹数据特征的分析和传统的单一函数挖掘的局限性,提出了基于基因表达式编程的频繁函数集挖掘的建模方法。该模型方法通过对历史飞行数据进行遗传算法的操作挖掘出数据集中对应的函数关系集合,用较好的函数模型预测未来航迹。以某一航班雷达数据为训练集做实验,结果表明了应用该方法的准确性和可用性。

自由飞行中的最优飞行轨迹

针对空中交通管制中的自由飞行方式,给出了一套轨迹优化算法,即动态规划法+共轭梯度算法、考虑风场的飞行器运动学方程等,算法根据即时的飞行任务(即应该通过的空域点)、天气情况(如风场)、威胁区信息(即不允许路过的区域)等,可以实时在线地规划出全局4-维最优飞行轨迹。轨迹优化的.性能指标是发动机燃料消耗量最小、或飞行时间最短、或路径(飞行路程)最短,或综合考虑各种性能指标等。该算法与软件包是基于Boeing-747飞机的数据作的设计与仿真测试。针对一些典型情况,给出了若干飞行轨迹优化的算例。该算法与软件包可用于有人驾驶的或无人自主控制的航空飞行器,如大型飞机等。

全太阳系深空探测轨迹全局优化(英文)

针对太阳系中全部的248997颗行星的探测问题,给出了一种关于探测飞行器的深空探测全局四维轨迹(t,x,y,z)优化方案,即飞行器从地球发射进入太阳系并采用小推力控制,优化方案的性能指标为飞行器与太阳系中全部行星中相遇和交会的星的数量最多并且燃料消耗最少。本方案给出了四维飞行轨迹进行全局优化的一套算法,该算法由搜索算法和四维轨迹优化算法组成。此搜索算法从太阳系的248997颗行星中寻找获得尽可能多的经过近地球3维走廊内的行星;而四维轨迹优化算法由改进的动态规划算法、基于最优控制理论的共轭梯度算法和静态参数优化算法组成,其中静态参数优化算法用于搜索最优发射时间窗口。基于该组合算法,通过长时间的大规模的飞行数字仿真,最终计算出探测器的四维最优飞行轨迹,在一年内路过了太阳系中全部行星中的12颗行星。

基于历史轨迹集的四维轨迹预测方法

针对传统空气动力学模型在预测飞机四维轨迹时误差较大的问题,提出了一种基于历史轨迹集的四维轨迹预测方法。首先,该方法运用空管基础数据、运动学模型、气象模型、管制意图计算创建历史轨迹集,然后使用实时的雷达航迹配对信息、气象信息、空中位置报、移交预达报等激励信息通过算法对历史轨迹集进行更新。最后,通过查询历史轨迹集预测完整的飞机四维飞行轨迹。仿真试验表明该方法比传统的空气动力学模型具有更好的实用性、准确性。

基于GEP的四维飞行轨迹预测模型

针对传统的空气动力学模型在四维飞行轨迹预测上误差较大的问题,提出了一种基于改进的基因表达式编程(GEP)的预测模型.该模型通过历史飞行时间数据找出飞行位置、高度和过固定点时间的函数对应关系,预测下次飞行过每个固定点的高度和时间,对全程采样固定点的预测实现完整的四维轨迹预测.仿真试验验证了该预测模型更为理想,更加符合实际情形.

基于时间最短的冲压机器人轨迹规划

针对一种4自由度串联冲压机器人的自动上下料过程,在机器人的初始位姿与目标位姿已知,而运动时间和路径不确定的前提下,以最大限度提高机器人工作效率为目标,以工程实际中关节驱动力、驱动速度和工艺过程为约束条件,进行了单工作周期时间最短优化研究。首先采用D-H参数法建立机器人的连杆坐标系,列出关节变换矩阵和运动学方程,通过微分变换法求出机器人的雅克比矩阵,采用牛顿-欧拉法得出各关节力矩的表达式;然后以时间为参数,运用5次多项式拟合关节位移变化轨迹;最后采用二分法求解满足各关节速度约束和力(矩)约束的最优运动时间,从而生成各关节运动轨迹,并且进行了对比实验。结果表明,该轨迹规划方法能有效地缩短冲压机器人的工作周期。

快速的飞行全过程航迹预测

该文提出一种面向空中交通管理的飞行全过程快速4-D航迹预测方法。以导航数据库和飞行计划为基础,对从起飞跑道至降落跑道的飞行全过程进行仿真预测。采用质点模型以保证预测速度;设计了终端区非精确定义航段之间的过渡轨迹保证结果完整性,考虑终端区高度及速度限制以保证结果真实性;基于WGS-84地理坐标系统进行航迹空间结构计算以保证结果准确度。仿真了北京首都机场至上海虹桥机场的飞行实例,并通过和实际飞行数据的对比验证了该方法的高效性。