液压型风力发电机组低电压穿越控制方法研究

以液压型风力发电机组作为研究对象,根据机组低电压穿越控制过程对液压系统功率快速调整的要求,以发电机稳定于工频转速和液压系统瞬态调整时间最短为控制目标,提出一种基于直接控制变量马达摆角的低电压穿越控制方法。以30kV·A液压型风力发电机组模拟实验台为仿真和实验平台,针对提出的低电压穿越控制方法展开研究,仿真和实验分析表明,直接控制变量马达摆角的方法具有较好的低电压穿越控制效果。     

基于压力反馈的液压型风机低电压穿越控制方法

结合液压型风力发电机组低电压穿越的控制要求,以实现低电压穿越过程中的功率快速调整为控制目标,提出了一种基于压力控制的低电压穿越控制方法,即在原有低电压穿越控制环的基础上加入压力控制环。通过AMESim和MATLAB/Simulink软件搭建仿真平台进行联合仿真,并依托30kV·A液压型风力发电机组半物理仿真实验平台进行实验验证。结果表明,所提出的控制方法既可实现功率的快速调整,也能有效地抑制并网转速的瞬态冲击。     

液压型风力发电机组低电压运行特性分析

以液压型风力发电机组为研究对象,分析机组在低电压工况下的运行特性。结合低电压穿越要求,完善并分析液压型风力发电机组工作原理。建立电压跌落时风力机、定量泵-变量马达液压调速系统以及发电机的暂态数学模型。以数学模型为基础搭建MATLAB/Simulink仿真平台,并在不同跌落深度下分别对三相电压等幅跌落、两相对地短路故障和单相对地短路故障进行低电压运行特性仿真分析。研究结果揭示了不同故障下机组低电压运行的特性规律,其中电流过载与电磁转矩产生脉振是机组低电压运行的重要表征现象。研究工作将为该机型低电压穿越控制提供一定的理论基础和技术手段。     

汽车传动系统扭矩突变工况的瞬态冲击分析

通过对汽车传动系统传动机理的分析,建立了12自由度多间隙非线性动力传动系统扭振模型,研究了各工况下的瞬态冲击响应特性。以主减速器齿轮角加速度作为瞬态冲击的评价指标,对比分析了离合器快速分离工况与急松驱动踏板工况的传动系统瞬态冲击响应特性。结果表明:发动机与传动系统的动力解耦会导致传动系统产生"震荡"现象。采用控制变量法研究了急松驱动踏板工况下扭转减振器扭转特性与传动系瞬态冲击强弱的对应关系,结果表明:离合器一级扭转刚度比二级扭转刚度对瞬态冲击强度的影响更大,通过调整一级扭转刚度降低传动系统瞬态冲击效果更加明显。     

插齿机主运动液压系统的仿真分析

以YS51200CNC插齿机主运动液压系统为研究对象,根据经典控制理论建立其控制阀数学模型,基于AMESim及Simulink软件建立液压系统联合仿真模型,并进行联合仿真分析。根据仿真结果,分析控制阀与液压缸间管道长度对液压系统响应特性的影响。利用PID调节器对伺服比例阀阀芯位置信号进行调节,有效地降低了系统的稳态误差,提高了系统的响应速度。     

基于AMESim管道参数对液压系统动态特性的影响分析

管道参数诸如直径、长度、材料等,对液压系统动态特性的影响常被设计者忽略,文中基于AMESim,针对连接器对接液压缸组的液压系统进行仿真分析,研究了管道长度、直径、材料对系统动态特性的影响,对系统的优化设计具有一定参考价值。     

液压型风力发电机组低电压穿越分层控制研究

为提高液压型风力发电机组的电网适应性和低电压穿越能力,针对机组低电压穿越过程中的能量调控问题,提出一种基于分层控制思想的低电压穿越控制方法,即设计出基于风力机调桨控制的顶层控制、基于变量马达摆角控制的中层控制和基于节流阀开度控制的底层控制。为实现机组在控制过程中多变量的协调控制,以风力机弃风最小、惯性储能最大和节流阀能耗最小为优化目标,采用二次规划算法对多目标控制律进行规划,得到了最优控制律。通过AMESim和MATLAB/Simulink软件对多目标控制策略进行仿真分析,利用液压型风力发电机组半物理试验平台对控制律进行了验证。结果表明,所提出的控制方法可以有效降低机组在低电压穿越过程中的剩余能量,降低对发电机的冲击,提高机组的适应性。     

基于AMESim的特高压断路器管道系统压力波动

针对特高压断路器管道系统中产生的液压冲击波对操动系统运行的影响,以蓄能器及其管道系统作为研究对象,在分析其压力波动产生机理的基础上,确立了管道子模型的选取原则,应用AMESim软件建立了液压系统的综合仿真模型,对模型进行求解后得到了液压管道的压力波动特性,同时分析了管道长度和内径对压力波动幅度的影响。研究结果表明：现有管道系统的压力波动幅度较大,不利于系统的稳定运行;对管道长度和内径组合进行优化设计后,压力波动的降幅在50%以上。所采用的研究方法对特高压断路器管道系统的优化设计具有参考价值。     

装载机行走静液压传动系统特性仿真与试验研究

静液压传动装置已被逐渐用于装载机的行走系统中,是由液压泵和液压马达组成的闭式液压传动系统。该文分析了装载机静液压传动系统的组成及工作原理,针对某4吨装载机研究了一种单泵-双马达行走静液传动系统。在AMESim环境下建立仿真模型,分析了静液压传动系统的特性。此外,还提出了一种针对单泵-双马达静液传动系统的变量调节规律,并将该规律在已经构建模型的基础上进行了仿真模拟。进行了某4吨装载机牵引特性试验,将仿真结果与整机试验进行对比,从而验证了静液传动系统仿真和变量调节规律的正确性。     

液压机械传动多领域虚拟样机集成与协同仿真

利用Pro／E、ADAMS、EASY5三种软件建立了液机械无级传动系统各子系统模型，完成了ADAMS／EASY5接口变量设计，将各子模型集成为ADAMS／EASY5协同仿真虚拟样机动力学模型。对液压机械无级传动系统纯液压段进行了协同仿真分析，得到了动力传动系统的动态特性曲线。本文的研究结论将为涉及多学科的液压机械无级传动系统的设计过程提供强大的支持，为其应用提供重要的理论依据。     

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...     

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...     

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。     

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。     

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.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

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。     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

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.     

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...