Aircraft-on-ground path following control by dynamical adaptive backstepping

The necessity of improving the air traffic and reducing the aviation emissions drives to investigate automatic steering for aircraft to effectively roll on the ground. This paper addresses the path following control problem of aircraft-on-ground and focuses on the task that the aircraft is required to follow the desired path on the runway by nose wheel automatic steering. The proposed approach is based on dynamical adaptive backstepping so that the system model does not have to be transformed into a canonical triangular form which is necessary in conventional backstepping design. This adaptive controller performs well despite the lack of information on the aerodynamic load and the tire cornering stiffness parameters. Simulation results clearly demonstrate the advantages and effectiveness of the proposed approach.     

基于干扰补偿的航天器直接自适应模糊控制

带有活动式有效载荷和挠性附件的大型航天器在动力学上具有非线性、大挠性、强耦合等特点,这给控制系统的设计带来了较大难度。其突出特点是要求控制系统在控制量受限的情况下克服各种未知复杂干扰力矩的影响。本文针对这类大型复杂航天器,提出了一种基于直接型自适应模糊逻辑和干扰补偿的控制方法。在控制律的设计中,将自适应模糊系统直接用作系统的主控制律,利用扩张状态观测器对模糊系统的逼近误差和内外干扰力矩进行观测并予以实时补偿。仿真结果表明了方法的有效性。     

扩频谱相关自适应滤波技术的研究

被高速伪随机码调制的扩频信号,其伪随机码是具有随机编码信号特征的周期信号。所以,扩频信号应被建模为周期信号(循环平稳信号)。循环平稳信号与其信号的频移副本之间具有很强的谱相关性,充分利用这种谱相关性可以实现对窄带和宽带干扰的抑制。基于循环平稳理论和自适应滤波理论,提出了一种基于改进的LMS算法的扩频信号谱相关自适应滤波技术。这种变步长的谱相关自适应LMS滤波器能实现对窄带和宽带干扰的抑制,仿真结果证明了其有效性。     

点接触圆柱蜗杆传动的设计原理

本文在对蜗轮副啮合原理分析的基础上,通过在共轭齿面上预先设置啮合位置,详细推导了失配齿面的几何参数和接触特性的计算公式,论述了点接触圆柱蜗杆传动的设计原理。应用本文的原理,采用优化综合的方法,可以使圆柱蜗杆传动直接实现点接触和完全互换,并具有良好的接触特性,使对误差的敏感性降低,缩短装配中的辅助时间,且传动质量得到改善。     

碳化物和硼化物陶瓷强韧化

从相复合、晶粒细化、裂纹改向和相变韧化角度论述了有关碳化物和硼化物的强韧化问题。     

Mesh deformation on 3D complex configurations using multistep radial basis functions interpolation

The Radial Basis Function (RBF) method with data reduction is an effective way to perform mesh deformation. However, for large deformations on meshes of complex aerodynamic configurations, the efficiency of the RBF mesh deformation method still needs to be further improved to fulfill the demand of practical application. To achieve this goal, a multistep RBF method based on a multilevel subspace RBF algorithm is presented to further improve the efficiency of the mesh deformation method in this research. A whole deformation is divided into a series of steps, and the supporting radius is adjusted in accordance with the maximal displacement error. Furthermore, parallel computing is applied to the interpolation to enhance the efficiency. Typical deformation problems of the NASA Common Research Model (CRM) configuration, the DLR-F6 wing-body-nacelle-pylon configuration, and the DLR-F11 high-lift configuration are tested to verify the feasibility of this method. Test results show that the presented multistep RBF mesh deformation method is efficient and robust in dealing with large deformation problems over complex geometries.     

基于分层策略的翼型多参量气动优化设计研究

与基于梯度的优化方法相比,遗传算法因其极强的鲁棒性、随机搜索及优化结果全局性等特点在工程优化中得到越来越广泛的应用。为提高优化设计的效率,改进了传统的遗传算法,采用并行分层策略基因遗传算法开展了翼型多参量气动优化设计研究,包括翼型和多段翼型的基因编码、外形参数化,以及动网格技术。结果表明,并行分层策略在得到较优气动优化结果的同时,极大地缩短了优化时间,提高了计算效率,具有广阔的工程应用前景。     

闪电防护铜网在航空复材制件VARI成型工艺中的树脂导流应用

复合材料在民机结构中的大量应用对航空复材制件的闪电防护提出了新的要求,与此同时,以VARI工艺为代表的复材液体成型技术愈发受到关注,常用导流网在VARI工艺中造成浪费也易引起质量问题,结合这两方面的需求,提出将闪电防护铜网用作导流介质,在表面应用类的航空复材制件的VARI成型工艺中,将铜网的闪电防护作用和树脂导流作用进行集成,并对闪电防护铜网在VARI工艺中的树脂导流作用进行了试验分析,研究了引入铜网导流后VARI制件的注胶情况、铜网层数对树脂渗透率的影响,以及制件最终成型效果和表面质量。本研究对于丰富复材VARI成型工艺技术手段,提升VARI工艺的综合经济性,进一步拓展VARI工艺在民机复材结构中的应用都具有积极意义。