半挂汽车列车高速侧倾稳定性控制研究

针对半挂汽车列车高速行驶易发生侧倾失稳现象,提出了一种挂车主动转向控制方法。建立挂车主动转向半挂汽车列车的五自由度动力学模型,基于最优控制技术设计了主动转向控制器。利用MATlAB软件编写了基于单点预瞄驾驶员模型的闭环运动仿真程序,对半挂汽车列车进行了运动学和动力学仿真研究。研究表明,挂车主动转向可显著提高半挂汽车列车的侧倾稳定性,但也在一定程度上牺牲了挂车的路径跟踪性能和汽车列车的横摆稳定性能。     

车身扭转柔性对半挂汽车列车侧翻影响的仿真分析

首先建立牵引车和半挂车的刚性车身半挂汽车列车模型,然后考虑车身的扭转柔性,将牵引车和半挂车的簧载质量分为前、后两部分,并建立各部分相互作用的方程,从而建立柔性车身半挂汽车列车模型。在MATLAB软件中建立半挂汽车列车的仿真模型,以横向载荷转移率和悬架侧倾角为判断指标,在角阶跃转向工况和鱼钩转向工况下分别对刚性车身和柔性车身半挂汽车列车模型进行仿真。对比仿真结果可知,车身的扭转柔性对半挂汽车列车的侧翻有较大影响。     

重型半挂汽车列车主动转向控制策略研究

为了提高重型半挂汽车列车的高速操纵稳定性,基于模糊控制和PID理论,提出了一种牵引车加挂车主动转向控制策略。首先,在MATLAB/Simulink软件中建立三轴重型半挂汽车列车的三自由度线性模型,并对模型有效性进行验证;其次,以三自由度线性模型与TruckSim非线性模型的牵引车横摆角速度偏差及偏差变化率为输入,设计了牵引车后轮主动转向模糊控制器,同时,以挂车横摆角速度偏差设计了挂车车轮主动转向PID控制器;最后,利用MATLAB/Simulink与TruckSim进行联合仿真,分别对牵引车加挂车主动转向控制、牵引车主动转向控制和传统无控制车辆进行双移线工况及重型铰接式车辆后部放大(Rearward Amplification, RWA)性能测试。结果表明,所设计的牵引车加挂车主动转向控制策略相比传统无控制车辆优势明显,有效减小了车辆横摆角速度、质心侧偏角和铰接角等值,牵引车与挂车最大横向位移偏差分别降低了13.75%和29.17%,且RWA比率降低了13.32%,显著提高了重型半挂汽车列车的高速路径跟踪性能及操纵稳定性能。     

超长型半挂车转向机构优化设计

从半挂汽车转向运动学关系出发，解决了重型汽车改型为超长半挂车的转向机构设计问题。首先对牵引车的转向机构进行优化设计，优化目标是最大程度地减少轮胎的磨损。同时分析了半挂汽车转弯时的运动学特征并确定了半挂车轴距的长度，以保证整个半挂汽车的稳定行驶。     

四轮转向半挂汽车列车鲁棒最优保性能控制

引入Gim轮胎模型建立四轮转向半挂汽车列车的四自由度非线性动力学模型。考虑轮胎侧偏刚度的不确定性,提出四轮转向半挂汽车列车直接横摆力矩的鲁棒最优保性能控制方案,基于模型追踪控制技术推导了直接横摆力矩的鲁棒最优保性能控制器。借助Matlab/Simulink软件,以建立的非线性动力学模型为平台,对该控制器的有效性进行了验证。仿真结果表明,高速大转向时,与传统二次最优控制相比,四轮转向鲁棒最优保性能控制方案可获得更好的控制效果,可显著提高半挂汽车列车的操纵稳定性。     

四轮转向半挂汽车列车横向稳定性的模糊PID控制

提出直接横摆力矩与四轮转向集成的控制方案。建立了四轮转向半挂汽车列车的四自由度非线性动力学模型,以零侧偏角为控制目标确定半挂汽车列车牵引车后轮转角,以牵引车横摆角速度为控制变量,基于模糊PID控制技术设计了直接横摆力矩模糊控制器。借助Matlab/Simulink软件,对该集成控制器的有效性进行了验证。仿真结果表明,高速大转向时,该四轮转向直接横摆力矩集成控制器能得到较好的输出响应,牵引车质心侧偏角、横摆角速度,半挂车横摆角速度及牵引车与半挂车的中心线夹角响应均能很快稳定,可显著提高半挂汽车列车的操纵稳定性。     

基于Trucksim软件的汽车列车动力学模型验证研究

首先基于MATLAB/SIMULINK软件建立半挂汽车列车的横摆侧倾运动学模型,然后基于Trucksim软件仿真平台对所建立的动力学模型进行验证。验证结果表明,所建立的横摆侧倾运动学模型精度满足要求,可用于汽车列车挂车主动转向控制器设计研究。     

半挂汽车列车操纵稳定性仿真研究

通过建立半挂汽车列车的动力学模型,对其进行拉氏变换,求出系统的传递函数;改变半挂汽车列车的使用和结构参数,利用MATLAB编程进行数字仿真,通过系统的传递函数求出其根轨迹;再根据根轨迹变化趋势,判断系统是否稳定及稳定裕度的大小;结果表明:车速、轮胎侧偏刚度、牵引车与挂车的质量、挂车质心到铰接点的距离、牵引车质心到铰接点的距离等参数,对半挂汽车列车操纵稳定性的影响程度不同,选择合理的参数可以提高半挂汽车列车的操纵稳定性。     

半挂汽车列车横向失稳的非线性动力学机制

半挂汽车列车载运工况变化较大,横向失稳机制复杂,给整车及稳定性控制系统的开发设计带来困难。应用非线性动力学的相关理论,研究半挂汽车列车在极限操纵工况下的平衡点分岔、相轨迹和Hopf分岔特性以及与载运工况的关系;在此基础上,结合不足转向梯度和系统阻尼特性对不同横向失稳形式的发生机制进行探讨。结果表明,载运工况的变化可能导致系统出现鞍结分岔、Hopf分岔和同宿轨道等非线性动力学现象;牵引车后轴侧滑而导致折叠是半挂汽车列车主要的横向失稳形式,挂车甩尾与折叠密切相关,挂车甩尾会同时加剧牵引车侧滑而加剧折叠,横向摆振与Hopf分岔密切相关,一般仅在载重较大且半挂车质心显著靠后才可能发生,且横向摆振失稳一般都会进一步发展到折叠而完全失控,选择牵引车横摆角速度和挂车侧偏角为控制变量设计稳定性控制系统有望取得较好的效果。     

雷达半挂汽车列车机动运输设计中的若干性能参数分析

针对半挂汽车列车的动力性、机动性、通性、稳定性、制动性等涉及的相关参数进行定性或定量的分析,并在假设牵引车、半挂车绕同一转向中心转向且为纯滚动的条件下,通过几何关系式,推导出半挂汽车列车转弯半径、通道宽度等计算公式。另外结合地面雷达车的运载特点和国、军标的相应要求,提出了在具体工程设计中应注意的事项。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...