Trajectory tracking of powered parafoil based on characteristic model based all-coefficient adaptive control

One of the primary difficulties in using powered parafoil(PPF) systems is the lack of effective trajectory tracking controllers since the trajectory tracking control is the essential operation for PPF to accomplish autonomous tasks. The characteristic model(CM) based all-coefficient adaptive control(ACAC) designed for PPF systems in horizontal and vertical trajectory control is proposed. The method is easy to use and convenient to adjust and test. Just a few parameters are adapted during the control process. In application, vertical and horizontal CMs are designed and ACAC controllers are constructed to control vertical altitude and horizontal trajectory of PPF based on the proposed CMs, respectively. Result analysis of different simulations shows that the applied ACAC control method is effective for trajectory tracking of the PPF systems and the approach guarantees the transient performance of the PPF systems with better disturbance rejection ability.

Design and simulation for large parafoil fix line object homing algorithm

Traditional parafoil homing usually uses a point as object. As the mobility of parafoil is limited by its glide ratio and wind, in some cases when the parafoil scatter area is large, or the glide ratio of parafoil is small, the deviation of its landing point to object point will be arduous to control. Accordingly, during these situations, when parafoil is used in recovery of spacecraft or satellite, the landing area of parafoil can be set as a rectangle, and the object of parafoil can be set as a line segment. The thesis of this work is designing an algorithm for parafoil homing using line segment as object. The algorithm of wind velocity and direction calculation in different flying segments was also investigated. The algorithm designed navigates the parafoil to land into the predestined area and largely reduce the probability of recovery loads falling to unwanted area to damage houses and people.

Dynamic modeling of a parafoil system considering flap deflection

In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigid body,a six degrees-of-freedom(DOF)dynamic model of a parafoil system including three DOF for translational motion and three DOF for rotational motion,is established according to the K rchhoff motion equation.Since the flexible winged paafoil system flying at low altitude is more susceptibleto winds,the motion characteristics of the parafoil system Wth and Wthout winds are simulated and analyzed.Furthermore,the ardropm test is used to further verify the model.The comparison results show that the simulation trajectory roughly overlaps with the actual flight track.The horzontnl velocity of the simulation model is in good accordance with the airdrop test,with a deviation less than0.5m/s,while its simulated vertical velocity fuctuates slightly under the infuence of the wind,and shows a similar trend to the ardrop test.It is concludedthat the established model can well describe the characteristics of the parafoil system.

Design and optimization in multiphase homing trajectory of parafoil system

In order to realize safe and accurate homing of parafoil system,a multiphase homing trajectory planning scheme is proposed according to the maneuverability and basic flight characteristics of the vehicle.In this scenario,on the basis of geometric relationship of each phase trajectory,the problem of trajectory planning is transformed to parameter optimizing,and then auxiliary population-based quantum differential evolution algorithm(AP-QDEA)is applied as a tool to optimize the objective function,and the design parameters of the whole homing trajectory are obtained.The proposed AP-QDEA combines the strengths of differential evolution algorithm(DEA)and quantum evolution algorithm(QEA),and the notion of auxiliary population is introduced into the proposed algorithm to improve the searching precision and speed.The simulation results show that the proposed AP-QDEA is proven its superior in both effectiveness and efficiency by solving a set of benchmark problems,and the multiphase homing scheme can fulfill the requirement of fixed-points and upwind landing in the process of homing which is simple in control and facile in practice as well.

NSGA Ⅱ based multi-objective homing trajectory planning of parafoil system

Homing trajectory planning is a core task of autonomous homing of parafoil system.This work analyzes and establishes a simplified kinematic mathematical model,and regards the homing trajectory planning problem as a kind of multi-objective optimization problem.Being different from traditional ways of transforming the multi-objective optimization into a single objective optimization by weighting factors,this work applies an improved non-dominated sorting genetic algorithm Ⅱ(NSGA Ⅱ) to solve it directly by means of optimizing multi-objective functions simultaneously.In the improved NSGA Ⅱ,the chaos initialization and a crowding distance based population trimming method were introduced to overcome the prematurity of population,the penalty function was used in handling constraints,and the optimal solution was selected according to the method of fuzzy set theory.Simulation results of three different schemes designed according to various practical engineering requirements show that the improved NSGA Ⅱ can effectively obtain the Pareto optimal solution set under different weighting with outstanding convergence and stability,and provide a new train of thoughts to design homing trajectory of parafoil system.

Research on the Aerodynamic Characteristics of Leading Edge and Bulge of Ram-Air Parafoil Based on CFD

This study focuses on the aerodynamic characteristics and flow mechanism of three different configurations of ram-air parafoil with open/closed air inlet and bulges. Firstly, we designed a special parafoil configuration for this study. Then we used numerical simulation to obtain the aerodynamic data of three parafoils at different angles of attack, and studied the influence of the bulge and the leading edge open/closed inlet on the aerodynamic performance of the ram-air parafoil. Finally, we study the flow mechanism of the ram-air parafoil through the pressure distribution and flow field. The results of the study show that compared with the aerodynamic parameters of the parafoil without bulges, the optimal angle of attack of the two parafoils with bulges is increased by 4?, the maximum lift to drag ratio of the parafoil with closed leading edge is reduced by about 4.3% and the optimal angle of attack is reduced by about 2?. The maximum lift to drag ratio of the parafoil with open leading edge is reduced by about 23.6% and the stalling angle of attack is reduced by about 4?. The pressure on the surface of a ram-air parafoil with open leading edge inlet is the highest. .

Research on parafoil stability using a rapid estimate model

With the consideration of rotation between canopy and payload of parafoil system, a four-degree-of-freedom（4-DOF） longitudinal static model was used to solve parafoil state variables in straight steady flight. The aerodynamic solution of parafoil system was a combination of vortex lattice method（VLM） and engineering estimation method. Based on small disturbance assumption,a 6-DOF linear model that considers canopy additional mass was established with benchmark state calculated by 4-DOF static model. Modal analysis of a dynamic model was used to calculate the stability parameters. This method, which is based on a small disturbance linear model and modal analysis, is high-efficiency to the study of parafoil stability. It is well suited for rapid stability analysis in the preliminary stage of parafoil design. Using this method, this paper shows that longitudinal and lateral stability will both decrease when a steady climbing angle increases. This explains the wavy track of the parafoil observed during climbing.

A new modeling scheme for powered parafoil unmanned aerial vehicle platforms: Theory and experiments

A novel framework is established for accurate modeling of Powered Parafoil Unmanned Aerial Vehicle(PPUAV). The model is developed in the following three steps: obtaining a linear dynamic model, simplifying the model structure, and estimating the model mismatch due to model variance and external disturbance factors. First, a six degree-of-freedom linear model, or the structured model, is obtained through dynamic establishment and linearization. Second, the data correlation analysis is adopted to determine the criterion for proper model complexity and to simplify the structured model. Next, an active model is established, combining the simplified model with the model mismatch estimator. An adapted Kalman filter is utilized for the real-time estimation of states and model mismatch. We finally derive a linear system model while taking into account of model variance and external disturbance. Actual flight tests verify the effectiveness of our active model in different flight scenarios.

基于空中回收的运载火箭尾舱挂取方案设计及仿真分析

运载火箭空中回收的挂取过程是整个回收过程中最关键的环节之一。针对运载火箭尾舱空中挂取的全流程,开展了将直升机作为回收平台的钩取装置设计,主要包括拉力传感器、过载保护装置、减载装置以及末端的执行机构。翼伞和减速伞从火箭尾舱的底部弹出,挂取装置可通过挂取翼伞顶部的牵顶伞实现对回收体的挂取操作。通过对挂取过程的仿真分析可以看出,回收体的质量增大时,过载显著增加,而当翼伞的收伞时间增加时,减载效果明显。

超大型组合翼伞与超大型连续翼伞的气动性能对比分析

随着航天回收系统应用需求越来越广,回收物质量也越来越大,对翼伞面积的要求越来越高,超大型翼伞开始受到广泛的关注,然而目前国内外对超大型翼伞的研究较少。对此,文章以超大型连续翼伞和超大型组合翼伞为研究对象,分别对其进行物理建模。采用计算流体力学(Computational Fluid Dynamics,CFD)的方法,基于k-epsilon湍流模型,分别计算在无下拉、单侧下拉、双侧下拉时超大型连续伞和超大型组合伞的气动特性。研究发现,超大型组合伞在组合处有很明显的气流补充,可以减缓流动分离的情况,增大失速迎角,更适合大攻角的飞行任务,适用范围更广。研究成果可以为以后超大型翼伞的选型提供一定的参考。

操纵方式对翼伞系统雀降性能的影响

为获得操纵方式对翼伞系统雀降性能的影响规律,建立了翼伞系统两体9自由度动力学模型,采用龙格库塔法进行了动力学编程计算,系统速度、翼伞及载荷姿态的数值结果和文献规律一致,最大误差为8.2%。开展了分级操纵及操纵速度对翼伞系统雀降性能的影响研究,得到了翼伞最小水平速度、最小垂直速度及最大迎角的变化规律。研究结果表明:一次操纵的雀降性能优于分级操纵;操纵时间过长或过短均会导致垂直速度增加;采用“先快后慢”和“匀速下拉”均能保证良好的雀降性能,操纵速度的选择应同时考虑最小垂直速度及翼伞飞行的稳定性。

风场下翼伞系统运动特性研究

为探究风场对翼伞系统运动特性的影响,建立了翼伞系统六自由度动力学模型,采用龙格库塔法对风场下翼伞系统运动特性进行了仿真计算。在此基础上,开展了翼伞系统在不同风向与不同飞行高度下运动特性变化的对比研究。结果表明:风场会改变翼伞空速,引起气动角变化,导致翼伞气动性能改变,使系统力、力矩不平衡,系统速度、姿态出现波动,而后重新恢复稳定,稳定后速度略大于无风时飞行速度与风速的矢量和;系统在顺风条件下前俯,逆风条件下后仰,侧风情况下会出现明显的滚转、偏航运动;飞行高度通过影响风速与大气密度改变系统平衡速度,高度越高平衡速度越大,但滑翔比与姿态角变化较小。文章所得风场下翼伞系统运动特性变化规律对翼伞轨迹规划及飞行控制有一定应用价值。

翼伞前缘的优化设计与气动分析

翼伞因其优秀的滑翔能力和气动性能在航空航天等领域有着广泛的应用前景,因此对翼伞的气动分析尤为重要。存在切口的前缘作为翼伞区别于机翼的重要特征之一,对翼伞前缘的分析及改进可以有效提升翼伞的气动性能。运用有限体积法对二维不可压缩雷诺时均Navier-Stokes方程进行求解,数值仿真数据与原始翼型试验数据基本吻合。计算结果表明:切口的存在干扰了翼型前缘的气流运动,具体表现在前缘上、下表面会有分离气泡的产生,降低了翼型的升力,同时大幅度提升了翼型的阻力;针对相同的切口,设计了前缘双唇部构型,并与原始切口翼型对比,改进的切口翼型在整个迎角范围内气动性能均优于原始切口翼型,前缘双唇部构型有效遏制了切口处分离气泡的产生,并在一定程度上延缓了切口翼型的失速。以上研究可为翼伞前缘的优化设计提供参考。

翼伞系统两体模型雀降操纵高度的优化

为减小翼伞系统的着陆速度,提高载荷的着陆安全性,提出了最优雀降高度确定方法,并完成相对雀降高度和着陆速度影响因素及计算模型研究。首先建立了翼伞-载荷系统两体九自由度动力学模型和雀降操纵耦合气动特性模型,更真实地模拟了翼伞-载荷两体之间操纵情况下的运动性能,研究了雀降操纵下翼伞系统的速度、姿态变化,数值结果和文献规律一致,滑翔比最大误差为8.20%。其次,基于该两体模型,以最小垂直着陆速度为优化目标,采用时间二分法确定最优雀降高度,分析了雀降操纵时机对着陆速度的影响。然后,开展了不同初始工况、翼载荷、着陆海拔高度、安装角下翼伞系统最优雀降实施的仿真计算,并采用最小二乘法完成了相对雀降高度、着陆速度的公式拟合。结果表明:初始参数对相对雀降高度几乎没有影响;随着翼载荷及着陆海拔高度的升高,着陆速度及相对雀降实施高度增加;安装角对着陆速度影响不大,但安装角的增大会引起雀降实施高度增加;所提出的相对雀降高度和着陆速度计算模型与仿真结果较为符合,最大误差小于4.00%,表明该计算模型有良好的适用性。

高滑翔伞伞绳叉联结构优化设计

为获得翼伞伞绳最优叉联结构设计方案,文章提出了1种高滑翔翼伞伞绳叉联结构的优化设计方法。首先,通过计算流体力学方法进行翼伞气动分析,确定最优气动性能时对应的伞绳安装角及翼伞伞衣气动载荷;然后,通过几何分析和受力分析,建立伞绳结点处的力系平衡方程及伞绳长度几何控制方程;最后,在满足伞绳结构安全的前提下,以伞绳总长度最小为优化目标,采用基于外罚函数和Davidon-Fletcher-Powell(DFP)算法原理的优化算法获得不同约束力条件对应的翼伞伞绳叉联点位置方案。优化结果表明:与优化前叉联方案相比,该方法伞绳长度可减小9.0%,阻力系数降低8.8%。此外,通过增加伞绳受力约束,可实现翼伞滑翔性能的进一步提高。

基于LBM的翼伞伞型曲面化气动特性研究

翼伞是应用于空降空投领域的一类重要气动减速装置,该文总体目标为采用格子玻尔兹曼方法研究不同翼伞曲面化伞型的气动仿真特性。在进行与试验数据的验证后,仿真分析不同伞型的气动曲线,得到其变化趋势和系数值差异。进行详细的流动特性分析对不同伞型的气动特性差异原因,还分析气室、小孔2种气流结构对气动特性的影响。采用传统有限元方法进行补充解释分析。结果充分证明格子玻尔兹曼方法进行翼伞气动仿真的可靠性。加入曲面化的伞型其升阻特性有明显提高,同时反映出气动特性的鲁棒性。气室结构对升阻特性提高有较大影响,而小孔结构影响程度较小。上述结论对翼伞试验和仿真研究具有重要的借鉴和指导意义。

基于原始自然算法的翼伞航迹规划研究

翼伞是一种对外部环境敏感性高的飞行器,在翼伞航迹规划中,需要考虑到风速和风向的变化以及地形高度的变化等因素来规划最优航迹。论文根据翼伞质点模型,对航迹规划中的约束进行数字化处理,包括风场、地形、威胁区、转弯半径等约束;将原始自然算法应用于翼伞航迹规划中并仿真验证了算法的合理性。相比于传统的航迹规划方法,基于原始自然算法的翼伞航迹规划技术具有更高的效率和更好的安全性,可以同时考虑多种外部因素干扰,以更好地适应不同的飞行环境。

基于双线性ADRC的翼伞系统三维航迹跟踪控制

目前翼伞系统的航迹跟踪主要针对二维路径,对于三维航迹跟踪的研究不多。针对翼伞系统6-DOF模型,采用具有天然解耦属性的自抗扰控制策略,设计一种基于双线性ADRC(B-ADRC)的三维轨迹跟踪控制方法。在水平面与纵向设计制导率与控制器,实现姿态与轨迹位置的跟踪,并对轨迹跟踪误差进行实时修正。跟踪过程中,将理想轨迹离散化获得一系列参考点,通过点切换的方式实现了复杂轨迹的跟踪。实验结果表明:所设计的双线性ADRC控制器能够实现对三维航迹的跟踪,具有良好的鲁棒性和抗干扰能力。

基于模型预测控制的翼伞航迹跟踪

翼伞是一种既可以在空中展开又可以在地面折叠的伞状装置,其具有的高度不稳定性和复杂气动特性给翼伞控制带来了很大挑战。本文提出了一种基于模型预测控制(MPC)的翼伞航迹跟踪控制方法。首先,建立了翼伞运动学和动力学模型,包括了翼伞的位置、速度、加速度等状态变量,以及翼伞运动受到的气动力和气动力矩。然后,采用模型预测控制方法,利用已知的翼伞模型和环境模型进行预测,通过优化算法计算出最优的控制输入,实现对翼伞航迹的跟踪控制。最后,通过仿真试验验证了所提出的控制方法的有效性。相比传统的翼伞跟踪方法,本文提出的方法显示出更优的跟踪性能,该方法能够有效抑制外部扰动的影响,具有良好的控制精度及鲁棒性,有一定的工程应用价值。

翼伞系统自主归航的关键技术研究综述

探究翼伞系统的建模、航迹规划和轨迹跟踪控制三项关键技术,以支撑翼伞系统的自主归航在大规模装备空投补给、运载火箭助推器回收和自然灾难救援等场合的广阔应用前景。通过调研国内外翼伞系统的发展,对其三项关键技术的基本原理、常用方法和前沿技术进行对比分析和归纳概括,重点包括翼伞系统在复杂环境下的柔性建模技术和障碍空间内的航迹规划技术以及基于智能控制策略的轨迹跟踪技术。对翼伞系统自主归航关键技术的未来发展趋势进行总结和展望,有助于对翼伞系统的自主归航研究形成总体性认知并掌握其发展动向,将对后续翼伞系统自主归航的研究具有启示作用和借鉴价值。