非线性控制系统的支持向量机辨识建模研究

针对非线性控制系统辨识建模难的问题,系统研究了基于支持向量机的非线性控制系统的辨识建模理论和方法,然后利用回归支持向量机(Support Vector Regression,SVR)设计了一个非线性控制系统的辨识建模系统.仿真试验结果表明,SVR具有很高的建模精度和较强的泛化能力,从而验证了该辨识方法的有效性和先进性.     

Synthesis,characterization and tribological properties of Cu/reduced graphene oxide composites

In this paper, nano-copper/reduced graphene oxide (Cu/rGO) composites were synthesized by the facile one step in-situ reduction method. The as-prepared Cu/rGO composites were characterized by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscope (XPS), X-ray diffraction (XRD) and Raman. Mechanism of reduction and growth of Cu/rGO composites were also discussed. The friction and wear properties of oleic acid (OA) modified composites as additives in poly-alpha-olefin (PAO) were investigated using four-ball wear tester.     

基于四端网络法的超声珩齿振动系统设计

从变截面杆作一维纵振动的运动方程出发,建立机械四端网络的数学模型及传输特性方程,导出了超声珩齿复合振动系统的频率方程和放大系数计算公式。将小端接圆柱杆的复合圆锥形变幅杆与被加工齿轮组成复合振动系统,将齿轮简化为圆柱杆,采用四端网络方法,得出了复合振动系统的频率方程与放大系数公式。     

基于键合图的变压预紧力电主轴热误差建模研究

高速电主轴工作过程中产生大量的热,导致主轴前端产生热变形,严重影响主轴加工精度.本文提出变压预紧力电主轴热误差预测模型,将传热学理论计算与键合图模型相结合,可实时且准确预测同类结构的电主轴热伸长.建立主轴的热-固耦合模型,通过有限元分析得到耦合作用下主轴温度场分布规律;根据温度场分布规律及热能流向,运用热力学理论将主轴...     

Thermal error prediction of motorized spindle for five-axis machining center based on analytical modeling and BP neural network

Journal of Mechanical Science and Technology - To ensure the stability of precision of the motorized spindle for five-axis machining center, the thermal error of five-axis machining center was...     

变压预紧电主轴热位移预测模型研究

为解决高速电主轴在变速过程中产生的热位移引起加工质量的问题,通过搭建变压预紧电主轴实验平台,提出一种不同预紧力下电主轴自然降速实验方法,基于能量守恒理论建立轴承摩擦生热模型,构建预紧力与轴承发热量的函数关系;在此基础上,进一步探究轴承温升导致主轴产生热位移的影响规律。分别以预紧力为1 450、1 550和1 700 N工况下,电主轴的轴承温度数据和时间作为输入,构建电主轴BP神经网络热位移预测模型。结果表明,构建的热位移预测模型能有效地预测电主轴的热位移,预测模型的残差在0.5μm以内,研究成果为高精密机床主轴热误差智能补偿提供一种新思路。     

基于约束图的三维实体建模研究

提出了一种新的三维建模方法:基于约束图的三维实体建模方法。该方法首先通过获取到的二维图形几何信息,对构成二维图形的图元进行识别和分类,然后建立起回转体之间的约束关系—几何约束图,实现了对二维图形进行自动识别。最后,利用三维约束形体布尔函数,在AutoCAD的VBA环境中实现三维建模。     

基于SIMULINK矢量控制系统的仿真

本文应用了一种优秀的仿真工具－ＳＩＭＵＬＩＮＫ,基于ＳＩＭＵＬＩＮＫ,对笼型异步电机矢量变换模型及以此模型为控制对象的矢量控制系统进行了仿真研究。详细构造了ＳＩＭＵＬＩＮＫ的仿真结构图,给出了仿真算法和仿真结果。     

An analytical study on prediction of effective properties in porous and non-porous piezoelectric composites

Eshelby type micromechanics model with a newly developed piezoelectric Eshelby tensor is proposed for predicting the effective electroelastic properties of the piezoelectric composite. The model is applied for piezoelectric solids containing both porosities and metal inhomogeneities. The effective electroelastic moduli of the composites such as stiffness, piezoelectric constants, and dielectric constants are predicted by the present model, which are extensively compared with the existing experimental results from the literatures. The validity of Eshelby type model for predicting the effective properties of the composite is thoroughly examined. It can be concluded from this study that a new mechanism is needed to compute correctly the dielectric constants among the effective properties of the composites.     

机床主轴系统热态及变形特性研究进展

从电主轴的轴承热态特性、主轴热态特性及刀柄变形特性等角度入手,分析了影响电主轴工作性能的若干关键技术,介绍了国内外电主轴相关技术的研究进展,指出了高速精密电主轴技术的发展趋势.     

Comprehensive measurement and evaluation system of high-speed motorized spindle

Reducing the manufacturing time is the trend of high-precision manufacturing, and the precision of a work-piece is very important for manufacturing industry. The high-speed motorized spindle is the most critical part and becoming more widely used in the machine tool at present, and its precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and effects of the spindle’s thermal deformations; hence, how to roundly measure and objectively evaluate high-speed spindle is an imminence question of it because the comprehensive dynamic properties and evaluation system of spindles directly affect the cutting ability of the whole machine tool before they are manufactured. This paper presents a comprehensive measurement and evaluation system of high-speed motorized spindle, which reflects the overall performance of motorized spindle and bases on international standard.     

基于UML的嵌入式系统可视化建模研究

本文阐述了统一建模语言UML的基本语法结构和建模步骤。利用UML建立完善的开发模型,有利于提升嵌入式系统的开发效率与质量。本文运用UML,借助其多视图表达方式,通过实例论述UML可视化建模方法在嵌入式系统开发过程中的具体应用。     

A new approach for rule extraction of expert system based on SVM

Based on the SVM’s excellent generalization performance, a new approach is proposed to extract knowledge rules from Support Vector Clustering (SVC). In this method, the first step is to choose the features of the sample data by using Genetic Algorithm for improving the comprehensibility of the knowledge rules. Then the SVC algorithm is adopted to obtain the Clustering Distribution Matrix of the sample data whose features have been chosen. Finally, hyper-rectangle rules are constructed using the Clustering Distribution Matrix. To make the rules more concise, and easier to explain, hyper-rectangle rules are simplified further by using rules combinations, dimension reduction and interval extension. In addition, the SMOTE (Synthetic Minority Over-sampling Technique) algorithm is adopted to resample fault samples in order to solve the serious imbalance problem of samples. The UCI datasets are used to validate the new method proposed in this paper, the results compared with other rules extraction methods show that the new approach is more effective. The new method is used to extract knowledge rules for aero-engine oil monitoring expert system, and the results show that the new method can effectively extract knowledge rules for expert system, and break through the bottleneck in expert system knowledge dynamic acquisition.     

Numerical modeling of nonlinear deformation of polymer composites based on hyperelastic constitutive law

Fiber reinforced polymer (FRP) composites exhibit nonlinear and hyperelastic characteristics under finite deformation. This paper investigates the macroscopic hyperelastic behavior of fiber reinforced polymer composites using a micromechanical model and finite deformation theory based on the hyperelastic constitutive law. The local stress and deformation of a representative volume element are calculated by the nonlinear finite element method. Then, an averaging procedure is used to find the homogenized stress and strain, and the macroscopic stressstrain curves are obtained. Numerical examples are given to demonstrate hyperelastic behavior and deformation of the composites, and the effects of the distribution pattern of fibers are also investigated to model the mechanical behavior of FRP composites.     

冷轧钢基复合材料复合工艺及复合机理的实验研究

对冷轧钢基复合材料的生产工艺过程进行了实验研究,并根据实验结果探讨了复合机理.实验结果表明,基材钢必须进行表面的毛化处理,表面粗糙度约为Rz=81～101 μm;钢-铝无张力复合轧制所需的总相对压下量ε0为40%≤ε0≤60%,钢-铜无张力复合轧制所需的总相对压下量ε0为ε0≥70%;钢-铝复合后退火温度在320℃左右时,保温时间应在1小时左右;钢-铜复合后退火温度在550°～600℃之间时,适宜的保温时间约为1.5小时.轧制产生机械嵌合,热处理消除内应力、形成一定厚度的合金层,从而使基材与复合材有机成为一体.     

Realization of parking task based on affine system modeling

This paper presents a motion control system of an unmanned vehicle, where parallel parking task is realizedbased on a self-organizing affine system modeling and a quadratic programming based robust controller. Because of non-linearity of the vehicle system and complexity of the task to realize, control objective is not always realized with a single algorithm or control mode. This paper presents a hybrid model for parallel parking task in which seven modes for describing sub-tasks constitute an entire model.     

基于纬度建模的钢铁企业成本系统建模方法

为准确表达客户需求、更好地与用户沟通并全面描述业务对象,提出了基于纬度建模的信息系统建模方法.该方法首先采用纬度模型描述用户需求,并采用IDEF0技术建立系统功能模型;针对纬度模型和多数据源建立IDEF1x模型,以指导数据库设计;通过统一建模语言技术对IDEF0中的节点进行业务链描述,并建立对象模型以指导软件系统设计.最后,以某钢铁企业的成本管理系统设计为例,通过分析成本管理业务模型,详细阐述了该建模方法对成本管理系统的设计过程的支持.实际应用证明了该方法的有效性和可行性.     

基于多智能体的制造系统生产控制建模研究

为提高制造系统生产控制的性能,建立了基于多智能体系统的混合控制模型.该模型把生产控制系统分为管理智能体层、单元智能体层和执行智能体层.管理智能体层负责调度和协调各单元智能体,并对所有智能体进行管理;单元智能体层中的各单元智能体间通过公用数据库相互协作;执行智能体对制造系统内的硬件负责,它们根据局部的本地资源信息及当前状态,接收发布的任务,并对其求解.同一层次的智能体之间是分布式结构.采用基于多智能体的混合控制模式,提高了制造系统生产控制的实时性和灵活性.通过激光拼焊生产系统中的试验,验证了该模型的有效性.     

基于Web的教材管理系统建模设计

教材管理是高校教务工作中的重要环节,本文根据“基于WEB的教材管理系统”的分析和建模,阐述了开发本系统的必要性和可行性。介绍了系统的UML静态模型的分析和建模过程,并详细介绍了系统功能的设计和突出优点,对相关管理系统的开发有一定的借鉴作用。