基于分布式自适应的多智能体容错一致性控制

针对"领航者-跟随者"的多智能体编队，由于领航者系统出现故障引起编队通讯中断而不能完成任务的问题，提出了一种基于一致性理论的分布式自适应控制方法，用于解决该问题。首先，以一个位于顶点的智能体作为领航者，其余3个位于同一条线上的智能体作为跟随者，由此所构成的三角形编队作为被控对象。其中，领航者速度方向作为编队的前行方向，跟随者位于领航者之后。其次，基于图论，对智能体局部信息参数进行分布式自适应更新，并设计分布式自适应控制律，用于弥补多智能体编队中领航者故障所造成的影响。同时，根据相邻智能体的局部信息，设计整体分布式自适应容错控制律，进一步通过构建合理的Lyapunov函数，证明所设计控制器的稳定性，以及"领航者-跟随者"之间相对横向以及相对纵向的距离误差均收敛于固定常数。最后，仿真验证表明：所提出的自适应控制方法具有良好的鲁棒性，这也为工程实践提供了理论依据。     

液体火箭发动机针栓喷注器雾化燃烧技术研究进展

针栓喷注器具有结构简单、可靠性高、燃烧稳定,可实现深度节流、面关机、机构可按比例缩放、成本低等显著优点,以其为基础的推力调节技术是一种实现液体火箭发动机变推力方案的有效途径,得到了广泛的应用。基于国内外针栓喷注器及针栓式发动机技术的发展现状和应用实例,着重从喷注器雾化性能和发动机燃烧流动问题2个方面进行了分析,在此基础上提出了对喷注器及发动机技术研究方向和研究重点的建议。     

民用飞机起落架缓冲器选型与对比分析研究

以民用飞机前起落架和主起落架为研究对象,首先运用Delphi和SQLServer开发了民用飞机缓冲器参数设计程序,计算了前起落架采用单腔定油孔型式和单腔变油孔型式、主起落架采用单腔定油孔型式和双腔定油孔型式的缓冲器的设计参数;然后基于ADAMS/Aircraft模块分别建立了前起落架和主起落架的虚拟样机,并进行落震仿真分析,仿真结果符合要求;最后通过仿真结果进行起落架缓冲器不同型式的对比分析。研究结果表明：单腔变油孔型式较单腔定油孔型式提高了缓冲器的缓冲效率、双腔定油孔型式较单腔定油孔型式在大的下沉速度下降低了缓冲器的过载。     

轴流式压气机近失速状态端壁流动时频分析

为准确辨识某型单轴涡喷发动机压气机近失速点的流动特征,对其端壁静压信号进行了时频分析。时频分析结果表明,近失速点的工况下,与其它各级相比,压气机第一级静子机匣壁面流动变化最为显著;随着发动机工作点沿共同工作线趋近喘振边界,压气机第一级静子机匣壁面静压信号中以550Hz为中心的宽带信号开始出现并逐步增强。所发现的压气机端壁流态特征可用于发动机节流过程中工作点接近失速边界的程度的判定,具有一定的工程应用价值。      

Critical Issues on Magnetic Reconnection in Space Plasmas

The idea of expedient energy transformation by magnetic reconnection (MR) has generated much enthusiasm in the space plasma community. The early concept of MR, which was envisioned for the solar flare phenomenon in a simple two-dimensional (2D) steady-state situation, is in dire need for extension to encompass three-dimensional (3D) non-steady-state phenomena prevalent in space plasmas in nature like in the magnetosphere. A workshop was organized to address this and related critical issues on MR. The essential outcome of this workshop is summarized in this review. After a brief evaluation on the pros and cons of existing definitions of MR, we propose essentially a working definition that can be used to identify MR in transient and spatially localized phenomena. The word “essentially” reflects a slight diversity in the opinion on how transient and localized 3D MR process might be defined. MR is defined here as a process with the following characteristics: (1) there is a plasma bulk flow across a boundary separating regions with topologically different magnetic field lines if projected on the plane of MR, thereby converting magnetic energy into kinetic particle energy, (2) there can be an out-of-the-plane magnetic field component (the so-called guide field) present such that the reconnected magnetic flux tubes are twisted to form flux ropes, and (3) the region exhibiting non-ideal MHD conditions should be localized to a scale comparable to the ion inertial length in the direction of the plasma inflow velocity. This definition captures the most important 3D aspects and preserves many essential characteristics of the 2D case. It may be considered as the first step in the generalization of the traditional 2D concept. As a demonstration on the utility of this definition, we apply it to identify MR associated with plasma phenomena in the dayside magnetopause and nightside magnetotail of the Earth’s magnetosphere. How MR may be distinguished from other competing mechanisms for these magnetospheric phenomena are then discussed.This revised version was published online in July 2005 with a corrected cover date.     

翼型结冰过程数值模拟验算与分析

应用FENSAP-ICE结冰计算软件,对NACA0012翼型进行了流动特性、水滴撞击特性以及冰型生成过程的计算;同时,对结冰前后的翼型进行气动力特性计算对比分析,其中包括升力特性对比、阻力特性对比、流场细节分析以及压力系数分布对比。计算结果表明：翼型前缘结冰后,导致翼型前缘气流提前分离,最大升力系数、失速攻角大幅减小,...     

风力机叶片顺风向风致振动研究

借鉴桥梁和高楼建筑上已经广泛应用的风工程方法,在考虑脉动风的随机性的条件下,从频域和时域两个角度讨论了风力机叶片极限位移的计算方法。文中采用了Shinozuka提出的谐波叠加法从脉动风功率谱得到一组脉动风的时程样本。风力机的叶片被简化为变截面梁来考虑。将选定的脉动风功率谱以及相应的里程样本作用在叶片上,运用频域和时域两套方法对叶片进行了计算和分析,得到叶片的顺风向振动的平均位移和极限位移结果。结果表明,频域和时域两套方法得到的结果基本一致。将所提出的方法用于工程应用中,分析了暴风停机状态下的叶片极限位移最不利情况。最后指出本文的方法是一般性的,可用于风力机叶片与塔架的耦合分析。     

HYBRID CARTESIAN GRID/GRIDLESS METHOD FOR CALCULATING VISCOUS FLOWS OVER MULTI-ELEMENT AIRFOILS

A hybrid Cartesian grid/gridless method is developed for calculating viscous flows over multi-element airfoils. The method adopts an unstructured Cartesian grid to cover most areas of the computational domain and leaves only small region adjacent to the aerodynamic bodies to be filled with the cloud of points used in the gridless methods, which results in a better combination of the computational efficiency of the Cartesian grid and the flexi- bility of the gridless method in handling complex geometries. The clouds of points in the local gridless region are implemented in an anisotropic way according to the features of the thin boundary layer of the viscous flows over the airfoils, and the clouds of points at the vicinity of the interface between the grid and the gridless regions are also controlled by using an adaptive refinement technique during the generation of the unstructured Cartesian grid. An implementation of the resulting hybrid method is presented for solving two-dimensional compressible Navier-Stokes （NS） equations. The simulations of the viscous flows over a RAE2822 airfoil or a two-element airfoil are success- fully carried out, and the obtained results agree well with the available experimental data.     

动边界问题无网格算法及其动态点云

提出基于Delaunay图映射的点云运动处理技术.该技术使点云随物体运动再生成问题变成简单的映射关系,无需迭代,且能保持点云结构不变,故有效地避免了因点云结构变动而产生的附加计算量.运用该技术,结合非定常Euler方程双时间步无网格算法,成功地模拟了翼型的跨声速非定常流动.其中物理时间迭代采用二阶隐式格式,伪时间遮代采用四步龙格一库塔显式格式.文中给出了不同翼型的计算结果,并与实验结果进行了比较,取得了令人满意的结果.     

基于OPC技术的点焊实时信息管理系统

采用OPC技术和SQL Senrer技术,运用VC＋＋构建了面向网络化生产的点焊实时信息管理系统。该点焊实时信息管理系统通过OPC客户接口实现从点焊OPC服务器获得点焊过程实时信息和焊接工艺规范信息,同时实现对焊接各种生产信息的有效管理。该点焊实时信息管理系统可以用于电阻焊网络化生产和质量管理。