临近空间大气压力传感器现场校准装置研究

本文针对临近空间大气压力传感器现场校准需求,介绍了临近空间大气压力传感器现场校准装置工作原理, 进行理论分析与仿真,提出需突破的关键技术,给出了不确定度预估。     

有翼再入飞行器的超/高超声速气动力工程方法

有翼再入飞行器气动力的工程计算方法尚有待进一步完善,计算精度有待进一步提高。文章根据有翼再入飞行器的气动布局特点,改进和发展了一套适于其气动布局的部件划分策略和压强计算选取准则。以此对航天飞机轨道器和类X-34飞行器的纵向气动力特性进行工程计算,并与其风洞试验和数值模拟结果进行对比分析。结果表明,文中的工程计算方法在马赫数3以上的超/高超声速范围内可准确预测有翼再入飞行器的升阻特性,其中升力系数和阻力系数误差小于10%;并可准确预测俯仰力矩特性随迎角改变的变化规律。与现有方法相比,文中的部件划分策略和压强计算选取准则在升阻特性精度相当情况下,可明显提高俯仰力矩的预测精度,并反映飞行器表面的压强分布特征。     

新能源汽车电机发展趋势及测试评价研究

为缓解能源短缺与环境污染问题,新能源汽车得到了迅速发展、推广,并成为当今汽车产业的重要研究方向。以新能源汽车电机的种类及国内外新能源汽车电机选型应用情况出发,对新能源汽车电机的发展趋势和对评价有关的测试项目作了分析研究。     

Prospects of sea launches for Chinese cryogenic liquid-fueled medium-lift launch vehicles

This paper introduces the sea-launch technology of a cryogenic liquid-fueled medium-lift rocket. It first reviews the current state of sea launch technology, and then gives a brief introduction of China’s New Generation Medium-lift Launch Vehicle (NGMLV). The innovations in the NGMVL, such as responsive test and launch control, a H³ launch model, and unmanned operations, provide convenience for sea launches. Based on these innovations, this paper proposes a sea launch scheme, including the system configuration, test and launch processes, and an improved adaptive design for the rocket. Then, the launch platform is discussed in detail, which integrates the functions of sea transportation, assembly and test, as well as technical and launch areas. The layout and function divisions, fluid filling, gas supply and distribution systems, and lossless storage technology of LH2 are described in order. This breakthrough in sea launch technology will enable China to launch medium and large satellites and constellations ‘both on land and sea’, especially into low-inclination Low-Earth Orbits (LEOs), and it allows China to remain competitive in the fast-paced space industry.     

高性能飞机发展对控制理论的挑战

根据笔者30余年来飞行试验研究的实践,从实际飞行的角度简要综述了影响飞行安全的大迎角过失速机动、超低空重载空投、飞行器突发故障和无人机控制方法研究。描述了操纵稳定性飞行试验获取飞机模型的手段和通常飞行控制器设计对模型的近似,给出了8个飞行鲁棒控制的研究问题;对超低空重载空投控制方法进行了描述,并给出了飞行器出现故障时突变模型和容错控制方法;同时,描述了测量对飞行控制特别是对保障无人机飞行安全的重要性,指出了飞行控制方法研究存在的部分问题,并建议有关高校研究单位从稳定性很好的四旋翼转向固定翼或单旋翼战术无人机等高层次研究。     

UAV navigation in high dynamic environments: A deep reinforcement learning approach

Unmanned Aerial Vehicle (UAV) navigation is aimed at guiding a UAV to the desired destinations along a collision-free and efficient path without human interventions, and it plays a crucial role in autonomous missions in harsh environments. The recently emerging Deep Reinforcement Learning (DRL) methods have shown promise for addressing the UAV navigation problem, but most of these methods cannot converge due to the massive amounts of interactive data when a UAV is navigating in high dynamic environments, where there are numerous obstacles moving fast. In this work, we propose an improved DRL-based method to tackle these fundamental limitations. To be specific, we develop a distributed DRL framework to decompose the UAV navigation task into two simpler sub-tasks, each of which is solved through the designed Long Short-Term Memory (LSTM) based DRL network by using only part of the interactive data. Furthermore, a clipped DRL loss function is proposed to closely stack the two sub-solutions into one integral for the UAV navigation problem. Extensive simulation results are provided to corroborate the superiority of the proposed method in terms of the convergence and effectiveness compared with those of the state-of-the-art DRL methods.     

Aerodynamic performance of owl-like airfoil undergoing bio-inspired flapping kinematics

Natural flyers have extraordinary flight skills and their prominent aerodynamic performance has attracted a lot of attention. However, the aerodynamic mechanism of birds' flapping wing kinematics still lacks in-depth understanding. In this paper, the aerodynamic performance of owl-like airfoil undergoing bio-inspired flapping kinematics extracted from a free-flying owl wing has been numerically investigated. The overset mesh technique is used to deal with the large range movements of flapping airfoils. The bio-inspired kinematics consist of plunging and pitching movement. A pure sinusoidal motion and a defined motion composed of plunging of sinusoidal motion and pitching of the bio-inspired kinematics are selected for comparison. The other two NACA airfoils are also selected to figure out the advantages of the owl-like airfoil. It is found that the cambered owl-like airfoil can enhance lift during the downstroke. The bio-inspired kinematics have an obvious advantage in lift generation with a presence of higher peak lift and positive lift over a wider proportion of the flapping cycle. Meanwhile, the bio-inspired motion is more economical for a lower power consumption compared with the sinusoidal motion. The sinusoidal flapping motion is better for thrust generation for a higher peak thrust value in both upstroke and downstroke, while the bio-inspired kinematics mainly generate thrust during the downstroke but produce more drag during the upstroke. The defined motion has similar lift performance with the bio-inspired kinematics, while it consumes more energy and generates less thrust. The unsteady flow field around airfoils is also analyzed to explain the corresponding phenomenon. The research in this paper is helpful to understand the flight mechanism of birds and to design a micro air vehicle with higher performance.     

盘旋跟踪地面目标小型无人机控制系统设计

针对一种大展弦比、V形尾翼常规布局小型无人机盘旋跟踪地面目标飞行的飞行控制策略进行了研究.采用了一种单轴光电探测系统修正视场纵向误差,无人机航向控制修正视场横向误差的控制方法.设计了一种自适应PID(Proportion Integration Differention)控制器,并通过对无人机六自由度非线性运动模型的建模分析,进行了控制律的仿真验证,并将算法融合在盘旋跟踪飞行实验中.仿真及实际飞行实验结果表明:该控制系统在突风等大扰动的影响下获得了良好的动态性能指标,并有效地抑制了飞机姿态通道对视轴通道的耦合影响,满足了飞行任务的需求.     

激光等离子体减阻技术研究进展

利用激光等离子体减小高超声速飞行器的气动阻力对节能和最大限度地提高飞行器性能具有重要的意义。简单概述了高超声速飞行器的军事需求及等离子体减阻技术的分类;总结了激光等离子体减阻机理的实验研究和数值模拟情况;讨论了等离子体能量、点火位置和形状等参数对减阻性能的影响,目前利用激光等离子体技术可以减小70%的波阻。针对中国的激光等离子体减阻研究工作,分析了目前国内外研究中存在的问题,提出了深入开展激光等离子体减阻机理研究等建议。