Streamwise vortex generation by the rod

The technology development related to aerodynamics is leading to ever increasing loads of wings, airfoils and turbine and compressor blades. The increase in aerodynamic forces is often leading to flow separation and depreciation of the aerodynamic performance of flying objects or propulsion systems. Flow control methods are required to avoid these negative effects. In the recent two decades the flow control by means of air-jet vortex generators has been also intensively investigated. In this method a streamwise vortex is introduced by an oblique jet. The necessity to supply air by a pipe system may be considered a disadvantage. In order to eliminate this feature, it has been proposed to put out a rod instead of a jet. It has been shown that the application of a rod can introduce the same effect as a jet, as long as the streamwise vortex generation is concerned and appropriate dimensions are used. The present paper focuses on the influence of rod vortex generators on a flow pattern downstream. The results presented here concern experimental and numerical investigations and provide guidelines for the design of a new flow control method dedicated mainly to external flows.     

基于双变量预测控制的表贴式永磁同步电机直接转矩控制系统

基于电压矢量幅值和相角为变量的表贴式永磁同步电机(SPMSM)定子磁链幅值和转矩表达式,给出了9个不同幅值和相角的备选电压矢量,采用预测控制计算得出施加不同电压矢量下一时刻的定子磁链幅值和转矩值,建立了基于磁链和转矩误差的目标函数,并选择使目标函数最小的电压矢量为作为下一时刻施加的最优电压矢量。仿真结果表明:在双变量预测控制下,SPMSM直接转矩控制系统运行良好,定子磁链轨迹为理想圆,磁链和转矩均符合控制要求,转速跟踪良好,定子电流波形正弦。进一步对比分析表明:与开关表和固定电压矢量选择策略相比,双变量预测控制能显著减小转矩和磁链脉动。与开关表相比,转矩脉动均方根误差降低了62.92%,磁链脉动均方根误差降低了45.05%,评价函数均值降低了60.30%；与固定电压矢量选择策略相比,转矩脉动均方根误差降低了22.40%,磁链脉动均方根误差降低了3.85%,评价函数均值降低了15.93%。     

Distributed intelligent self-organized mission planning of multi-UAV for dynamic targets cooperative search-attack

This article studies the cooperative search-attack mission problem with dynamic targets and threats, and presents a Distributed Intelligent Self-Organized Mission Planning (DISOMP) algorithm for multiple Unmanned Aerial Vehicles (multi-UAV). The DISOMP algorithm can be divided into four modules: a search module designed based on the distributed Ant Colony Optimization (ACO) algorithm, an attack module designed based on the Parallel Approach (PA) scheme, a threat avoidance module designed based on the Dubins Curve (DC) and a communication module designed for information exchange among the multi-UAV system and the dynamic environment. A series of simulations of multi-UAV searching and attacking the moving targets are carried out, in which the search-attack mission completeness, execution efficiency and system suitability of the DISOMP algorithm are analyzed. The simulation results exhibit that the DISOMP algorithm based on online distributed down-top strategy is characterized by good flexibility, scalability and adaptability, in the dynamic targets searching and attacking problem.     

基于ICKF的永磁同步电机无传感器控制方法

针对在永磁同步电机(Permanent magnet synchronous motor,PMSM)中安装传感器带来的高成本、体积增大、可靠性降低和易受环境干扰等问题,提出采用迭代容积卡尔曼滤波(Iterative cubature Kalman filter,ICKF)算法来估计电机转速和转子位置,并将其应用于永磁同步电机无传感器控制。首先,建立了PMSM在α-β坐标系下的离散数学模型。其次,在Matlab/Simulink环境下分别建立了基于容积卡尔曼滤波(Cubature Kalman filter,CKF)和ICKF的PMSM转速、电流双闭环的无传感器矢量控制系统仿真模型,并进行了给定转速和加负载两种工况的仿真验证。最后,基于TMS320F28335芯片搭建了硬件实验验证平台。仿真分析与实验结果均表明,迭代容积卡尔曼滤波算法应用于永磁同步电机无传感器控制中抗负载变化干扰性好、电机运行稳定、电机转速和转子位置估计精度高,可满足对电机精确控制要求较高的应用场合,具有重要参考价值和推广意义。     

航天器内带电效应的微弱电流监测技术

航天器的内带电效应是影响其在轨稳定运行的重要因素。内带电效应的电流监测可以直接获得一手的内带电效应监测数据,也可获得反映引起内带电效应的高能电子充电环境的状态。针对近地中高地球轨道环境,基于国外电流监测数据并考虑可能遭遇的高能电子暴环境,分析获得了内带电效应电流的测量范围10 fA～500 pA。针对未来中高轨及木星、火星等深空探测任务内带电监测需求,提出了一种微弱电流监测方案,实现了pA级微弱电流测量模块的实验室模拟标定。标定结果表明,在10 fA～500 pA范围内,输入电流与输出测量电压之间的线性度较好。     

Solar sails for perturbation relief: Application to asteroids

A major cause of spacecraft orbital variation comes from natural perturbations, which, in close proximity of a body, are dominated by its non-spherical nature. For small bodies, such as asteroids, these effects can be considerable, given their uneven (and uncertain) mass distribution. Solar sail technology is proposed to reduce or eliminate the net secular effects of the irregular gravity field on the orbit. Initially, a sensitivity analysis will be carried out on the system which will show high sensitivity to changes in initial conditions. This presents a challenge for optimisation methods which require an initial guess of the solution. As such, the Genetic Algorithm (GA) is proposed as the preferred optimisation method as this requires no initial guess from the user. A multi-objective optimisation is performed which aims to achieve a periodic orbit whilst also minimising the effort required by the sail to do so. Given the system sensitivity, the control law for one orbit is not necessarily applicable for any subsequent orbit. Therefore, a new method of updating the control law for subsequent orbits is presented, based on linearisation and use of a Control Transition Matrix (CTM). The techniques will later find application in a multiple asteroid rendezvous mission with a solar sail as the primary propulsion system.     

基于成本控制的机队优化配置方法

为了控制航空公司运营成本,实现燃油成本和机组时间成本最小,建立多目标整数规划模型,分析各成本因素所占比例,考虑旅客市场需求、航线频率限制、机队飞机寿命限制及飞机适航限制等因素,并采用层次分析法对模型进行求解。通过算例分析和评价,实现航线资源与机队的最优配置,为航空公司降低可变成本提供理论依据。     

飞机数字化装配系统中机身交点孔加工方法研究

针对传统交点孔加工方法加工精度低且存在回弹变形的问题,设计了一种满足飞机大部件数字化装配要求的机身交点孔精加工方法,根据交点孔的加工特性完成了机身定位与固持、数控加工中心定位以及加工工艺的总体设计,确定了交点孔加工程序原点的计算方法和编程原则,最后通过交点孔试切加工试验验证了加工方法的可行性。     

展向离散抽吸法控制边界层转捩实验研究

通过实验成功发展了一种生成大振幅稳定条带的有效方法,即展向离散抽吸方法。在此基础上,开展条带控制边界层转捩的研究。实验在水洞中进行,以零压力梯度平板边界层为研究对象,利用氢气泡时间线法观测引入条带前后人工激发转捩边界层中扰动发展变化,分析条带对转捩的控制效果及参数影响。结果表明,展向离散抽吸方法生成的稳定条带最大振幅可达28.4%U（U为自由流速度）;实验中引入的宽度14和28mm的稳定条带都能起到抑制转捩的作用;条带振幅越大、宽度越窄,抑制效果越明显。研究结果为探索降低水/空气中航行器摩阻的新技术提供有价值的参考。     

带有引诱角色的多飞行器协同最优制导方法

考虑我方高价值飞行器面临对方拦截器拦截时,发射两枚防御器对拦截器进行拦截的情形。针对对方拦截器采用扩展比例导引律,在4个飞行器均具有一阶线性动力学特性假设下,基于最优控制理论设计了能在拦截末端施加相对拦截角的显式协同制导律。显式协同制导律将高价值飞行器和两枚防御器三者的协同考虑在内,给出了三者最优控制输入的解析解。仿真结果表明,设计的制导律能使两防御器成功拦截敌方拦截器,且在拦截末端施加一个相对拦截角。通过与只考虑两防御器协同的隐式协同制导律进行比较,可发现显式的协同制导律在控制要求和能量消耗上,要优于隐式的协同制导律。此外,还验证了在不同发射条件下的协同制导律的稳定性。