大型矿用挖掘机国产化电气系统优化设计

大型机械正铲式电动挖掘机(俗称"电铲")作为大型露天矿主要剥离和采装设备,关乎露天矿山生产效益和人员设备安全,其电气系统及其核心设备长期被国外厂商垄断,且多为进口通用工业设备的简单集成,存在固有的系统设计缺陷和适应性问题以及后续使用中的诸多问题等.本文基于神华准能集团露天矿电铲电气系统国产化升级改造成功经验,阐述了国产...     

Stability and bifurcation in network traffic flow: A Poincaré map approach

Previous studies have shown that, in a diverge-merge network with two intermediate links (the DM network), the kinematic wave model always admits stationary solutions under constant boundary conditions, but periodic oscillations can develop from empty initial conditions. Such contradictory observations suggest that the stationary states be unstable. In this study we develop a systematic approach to investigate the stability property of stationary states in this and other networks within the framework of network kinematic wave theories. Based on the observation that kinematic waves propagate in a circular path when only one of the two intermediate links is congested, we derive a one-dimensional, discrete Poincaré map in the out-flux at a Poincaré section. We then prove that the fixed points of the Poincaré map correspond to stationary flow-rates on the two links. With Lyapunov’s first method, we demonstrate that the Poincaré map can be finite-time stable, asymptotically stable, or unstable. When unstable, the map is found to have periodical points of period two, but no chaotic solutions. We further analyze the bifurcation in the stability of the Poincaré map caused by varying route choice proportions. We apply the Poincaré map approach to analyzing traffic patterns in more general (DM)ⁿ and beltway networks, which are sufficient and necessary structures for network-induced unstable traffic and gridlock, respectively. This study demonstrates that the Poincaré map approach can be efficiently applied to analyze traffic dynamics in any road networks with circular information propagation and provides new insights into unstable traffic dynamics caused by interactions among network bottlenecks.     

基于卡尔曼滤波的磁偶极子目标张量定位

采用现有单点磁梯度张量定位方法定位磁偶极子目标时,易出现定位结果受测量噪声影响而发散的现象。针对该方法的不足,根据磁偶极子磁感应强度与磁场梯度张量的基本关系式,建立张量定位的状态空间模型,并采用卡尔曼滤波器对状态向量进行估计,实现目标定位。设计数值算例对定位方法进行检验,定位结果表明,基于卡尔曼滤波的定位方法具有较高的精度和稳定性,可用于航空磁探测和水下小目标磁场探测。     

盾构主驱动减速机国产化开发研究

基于国内外减速机发展概况及盾构主驱动减速机国产化研究的现状,提出盾构主驱动减速机国产化不仅是我国盾构行业发展的迫切需要,同时具备一定的国产化条件。在对LOVAT 246盾构主驱动减速机前期使用过程中出现的故障现象进行统计分析的基础上,针对所出现故障的特殊性,从材料选用、齿轮模数与尺寸、轴承优化选型等方面进行国产化研究。经过现场试用后,其样机性能完全满足盾构正常掘进需求。盾构主驱动减速机国产化开发研究,对提升我国盾构技术水平有着重大意义。     

混沌映射在彩色图像水印中的应用

提出了一种新的基于混沌理论的彩色图像水印方法.在空域中RGB色彩空间的蓝色信道里嵌入水印以提高水印隐性和鲁棒性.水印的检测同样只在蓝色信道里进行,通过相关性的比较来确定结果.实验结果表明,文中所提出的水印方法速度快、易于实现,具有较高的安全性,并对包括剪裁在内的几何攻击有很好的鲁棒性.     

An range-free localization scheme for large scale underwater wireless sensor networks

In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited bandwidth, the severely impaired channel and the cost of underwater equipment all make the underwater localization problem very challenging. Exact localization is very difficult for UWSNs in deep underwater environment. We propose a range free method based on mobile detachable elevator transceiver (DET) and 3D multi-power area localization scheme (3D-MALS) to address the challenging problem. In the proposed scheme, the ideas of 2D multi-power area localization scheme (2D-ALS) and utilizing DET are used to achieve the simplicity, location accuracy, scalability and low cost performances. The DET can rise and get down to broadcast its position. And it is assumed that all the underwater nodes underwater have pressure sensors and know their z coordinates. We evaluate the performances of 2D-ALS and our proposed 3D-MALS schemes under both ideal and non-ideal channel propagation conditions, in terms of localization error and localization ratio. The simulation results show that our proposed scheme is much more efficient than the 2D-ALS.     

Constrained submap algorithm for simultaneous localization and mapping

When solving the problem of simultaneous localization and mapping (SLAM), a standard extended Kalman filter (EKF) is subject to linearization errors and causes optimistic estimation. This paper proposes a submap algorithm, which builds a weighted least squares (WLS) constraint between two adjacent submaps according to the different estimations of the common features and the relationship between the vehicle poses in the corresponding submaps. By establishing the constraint equation after loop closing, re-linearization is implemented and each submap’s reference frame tends to its equilibrium position quickly. Experimental results demonstrate that the algorithm could get a globally consistent map and linearization errors are limited in local regions.     

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针对城市交通管理控制中对于宏观交通状态分析的需求,提出了一种新型的大范围交通状态观测分析方法。首先依据路网中各个路口的综合交通状态值,利用逐点内插法,得到整个路网范围内各个路口之间区域的虚拟交通状态值,并通过状态值到色彩值之间的映射变换生成直观生动描述大范围路网交通状态的交通状态伪色彩图;接着利用Otsu图像分割算法,将交通状态伪色彩图进行分割,自动发现其中的拥堵区域;随后利用基于梯度的光流法,提取出图中呈现出的典型交通状态演化模式,用于指导宏观交通管理和控制;最后,利用北京市实际的交通数据进行的仿真研究证实了该算法的有效性。     

Development of an intelligent CAE system for auto-body concept design

The concept design phase is a critical step in auto-body design, as it has a great effect on later design work. This paper describes the implementation of an auto-body structure design in the early stages of a new auto-body developing program. In order to reduce the long design period and analysis error that plagues traditional auto-body concept design, an intelligent CAE system has been successfully developed and implemented based on the UGS NX/API opening platform. This system, the so-called ACD-ICAE (Auto-body concept design-intelligent computer aided engineering) System that means concept design-intelligent computer aided engineering system, employs a fully parametrized template method to build the conceptual auto-body geometry model and FEM model quickly and easily. It also integrates auto-body modeling, analysis and optimization on only one CAD platform via a parametric variables database. Moreover, all parametric variables are shared and updated in different phases of the ACD-ICAE System. A wizard User Interface (UI) based on knowledge of auto-body engineering was developed and used in this system. The procedures implementing the functional diagram of the ACD-ICAE system are also provided. A typical example of a car body concept design with four doors shows that the ACD-ICAE system is efficient and accurate.     

带阻尼失谐周期多跨连续梁的振动局部化问题

利用传递矩阵法分析研究了带阻尼失谐周期多跨梁中的振动局部化现象,将阻尼和失谐对于近周期结构的动力性能的影响进行了比较,并分析了两者同时存在时引起的综合效应与它们各自的影响之间的关系．结果表明：在无阻尼周期结构中处于“通频”范围内的振动能够传遍整个结构而不会发生衰减,但当结构中存在阻尼或失谐时,同样的振动在传播过程中将会发生指数衰减．