装载机虎头结构焊接顺序优化数值模拟分析

装载机虎头存在突出的焊接变形问题,为了减小焊接变形,得到最优焊接顺序方案,利用热弹塑性有限元方法建立了有限元模型,并对装载机后车架虎头结构焊接变形进行了数值模拟计算.分析了虎头结构的四种变形趋势,定量地对比了不同焊接顺序下虎头结构各部位的最大焊接变形点,得到优化的焊接顺序.该顺序模拟结果:侧臂最大挠曲变形量为8 mm,框架扭转变形量为4 mm,侧臂收缩变形为12 mm.对预测的最佳焊接顺序下的变形模拟值和实测值进行了对比,结果表明,两者吻合良好.     

小型地面移动机器人运动学分析及控制研究

研制了一种带前摆臂结构的小型地面移动机器人,建立了该机器人的运动学模型,确定了该机器人驱动轮转角与机器人位姿间的关系,为小型地面移动机器人的控制系统的设计提供了理论依据.该机器人的控制系统采用上下位机控制方式实现了对机器人的遥控控制,即上位机为 PC 机,下位机采用单片机.采用流向控制标志位查询判断驱动信号的流向,使机器人移动载体、摆臂和摄像装置的驱动电机可以协调运动.对该机器人各机构的运动进行了仿真,并得到了机构匀速运动过程中的主驱动轴转角、摆臂转角及摄像头转角等 3 个主要机构的运动参数曲线,验证了机器人各机构的运动性能.     

机器人机构运动学方程的完全解及其运动设计方案的优选

简述了一种能求得非线性方程组完全解的数值方法－－连续法的基本原理及其发展状况，该方法既能可靠求得机械运动学方程的全部精确解。又有用于求机构优化设计的全部优化解，从而有利于机构运动设计方案的优选，同时对其他各学科中的非线性问题的求解也具有重要参考价值。     

包装机切纸机构的计算机辅助设计及运动分析

为了实现方便针自动包装机切纸机构的预期功能,用解析法对其中的凸轮机构进行了计算机辅助设计.推导出了切纸机构中执行构件的位移、速度、加速度计算公式,在MATLAB环境下对该机构组合系统的运动参数进行了计算,给出了执行构件的位移线图、速度线图和加速度线图.运动分析结果表明切纸机构满足设计要求.     

一种新型并联机械手的正、逆模型分析

结合虚轴机床的结构特点,运用矢量法推导了两平动自由度机械手位置的正、逆解解析模型,满足机械手的实时控制要求,解决了数控系统中轨迹控制和位置显示问题。研究成果已成功地应用于一台新型并联机械手的开发。     

Kinematic synthesis of a robot with five degrees of freedom

Abstract

This paper studies the geometric design of a robot with five degrees of freedom. According to kinematic synthesis procedure, an industrial robot with five degrees of freedom was used as an example to illustrate the design concept. From the number synthesis point of view, the robot is one freedom less than adequate to perform a general three dimensional motion. The lack of full degree of freedom will restrict the available twist screws for the end‐effector. The unavailable twists of the robot were discovered based on the reciprocal screw system. Singular configurations of the robot were also examined. The dimensional synthesis of a robot is to decide the joint parameters to obtain a good workspace shape and volume. So far, there are no better rules which govern the relations between the joint parameters and the generation of workspace. Under this circumstance, the workspace geometric properties of a robot provide quantitative evaluation of the success of the dimensional synthesis. In this paper, workspace volume and other workspace properties such as the normalized volume index (NV1), volume centroid, and the higher volume moment of inertia are computed. The volume centroid gives the symmetric nature of the workspace, whereas the higher moment reveals the distribution and the compactness of the workspace valume.     

基于灰色预测与滑模变结构的ABS仿真分析

为研究汽车制动防抱死系统(antilock brake system,ABS)的超前性、实时性与鲁棒性,结合灰色预测和滑模变结构控制方法,提出基于灰色预测GM(1,1)模型与滑模变结构控制的ABS综合控制算法,建立仿真模型进行数据的对比分析.结果表明:相对于单滑模或bang-bang控制,灰色预测与滑模变结构综合控制方法使汽车ABS超前运行,缩短了制动时间与制动距离;有助于缓解滑模变结构方法自身带来的抖动缺陷.因此,灰色预测与滑模变结构综合控制方法有助于提升ABS的响应速度、实时鲁棒性与人体舒适性.     

Manufacturing process analysis with support of workflow modelling and simulation

Process analysis is recognized as a major stage in business process reengineering that has developed over the last two decades. Manufacturing process analysis (MPA) is defined as performance analysis of the production process. A manufacturing process analysis framework is outlined with emphasis on linking a company's strategy to operational process. Two issues, namely process modelling and simulation based analysis, are investigated. A compound workflow model (CWM) is proposed to provide graphic presentation of the production process that can be easily understood. Also it can be used directly by simulation to study the impacts of scheduling policy and analyse the process performance. A two-stage simulation analysis method is provided to quantitatively and efficiently define cause-and-effect relations to identify drivers for improvement. The manufacturing environment, PSC (production planning, scheduling and control) factors and the process structure are three main concerns considered in the simulation. An example is discussed in the final part of the paper.     

水泥混凝土道面结构在多轮荷载作用下的响应分析

为研究多轮荷载作用下对道面结构的响应,以ABAQUS分析软件为基础,采用多层结构的线弹性材料,建立了9块水泥混凝土面层板的"软弱地基-道面结构-飞机轮载相互作用"三维有限元模拟模型,建模过程中考虑了纵向横向接缝的传荷能力,为大型飞机轮载作用下的道面结构体系及其力学响应研究提供了先进、可靠的分析平台。     

Experimental investigation on the effects of process parameters of GMAW and transient thermal analysis of AISI321 steel

Gas metal arc welding (GMAW) develops an arc by controlling the metal from the wire rod and the input process parameters. The deposited metal forms a weld bead and themechanical properties depend upon the quality of the weld bead. Proper control of the process parameters which affect the bead geometry, the microstructures of the weldments and the mechanical properties like hardness, is necessary. This experimental study aims at developing mathematical models for bead height (HB), bead width (WB) and bead penetration (PB) and investigating the effects of four process parameters
viz: welding voltage, welding speed, wire feed rate and gas flow rate on bead geometry, hardness and microstructure of AISI321 steel with 10 mm thickness. The transient thermal analysis shows temperature and residual stress distributions at different conduction and convection conditions.     

六轮移动机器人运动学建模与仿真

针对石化行业的需求,设计了一款具有较强运动灵活性的适合在狭小空间、复杂环境中工作的六轮移动机器人。采用4个全向轮与两个普通橡胶车轮混搭的车轮配置方案,建立机器人的运动学模型,并分析了车轮的运动参数与机器人本体位姿之间的关系;运用ADAMS仿真软件构建了机器人的仿真模型,通过对直线行驶、原地转向性能进行运动学仿真,得到了机器人的运动学曲线,验证了运动学理论模型的正确性和机器人机构设计的合理性。原地转向误差实验表明,机器人具有较强的原地转向能力,原地转向最小误差可达到2.299mm,较好地满足了该机器人的高灵活性需求。     

模块化六自由度机器人运动学标定与实验研究

针对自主研发的模块化六自由度轻载搬运机器人,使用激光跟踪仪并采用直接标定法进行了运动学标定与实验研究。采用D-H法构建了机器人连杆坐标系和机器人运动学模型,并运用微分变换的方法建立误差模型。通过激光跟踪仪测量机器人末端位置,将其与运动学模型求解得到的机器人末端位置进行比较,验证了误差模型的正确性。然后将误差模型计算得到的机器人连杆参数误差在机器人控制系统软件中进行修正。最后利用激光跟踪仪测量机器人的关节转角间隙误差,将误差值转换成脉冲数并在软件中进行补偿。机器人运动学标定实验表明,使用激光跟踪仪进行连杆参数误差补偿和关节转角间隙误差补偿可以明显的减小绝对定位误差,绝对定位误差降低了69.6%,定位精度有了明显的提高。     

新型3-RRC并联机器人机构精度分析

 根据三平移并联机器人机构运动学位置反解,利用微分理论建立了该并联机器人机构的精度模型。通过计算机仿真,分析了主动副的转动误差、结构参数误差和位姿变化对机器人机构精度的影响,为该机器人机构实际误差补偿与控制提供理论依据。     

Application of defect simulation as a tool for more efficient failure analysis

In modern VLSI processes, increasing process complexity has resulted in an exponential rise in the costs of thorough failure analysis. In this paper, we present a defect simulation-based failure analysis methodology, which can be used to significantly reduce both costs and turn-around time for failure analyses. The methodology is based on the ability to generate a defect dictionary, which can relate defect characteristics to some easily measurable symptoms of defect occurrence.     

转盘式多足仿生机器人的运动学分析及优化

为解决多足机器人控制系统复杂、加工装配困难的问题,设计了一种基于单自由度Jansen连杆机构的转盘式多足仿生机器人,并对其进行运动学分析和优化。首先,运用旋量理论对机器人的单条仿生机械腿进行自由度验证,并运用复数矢量法对仿生机械腿进行运动学求解,得到其足端运动轨迹方程及各关节的转动角度。然后,基于仿生机械腿足端的运动轨迹及其影响因素,分析了其优化方向。接着,提出了转盘式传动机构,并对仿生机械腿的转动关节和足端进行了优化,同时利用SolidWorks软件对转盘式多足仿生机器人的步态进行了时序分析。最后,制作了转盘式多足仿生机器人样机并分析了其在常规路况下的运动能力,验证了其可行性。结果表明,改变曲柄长度和机架水平倾角可优化多足仿生机器人的运动轨迹,使其更符合实际应用所需;转盘式传动机构与多条仿生机械腿的叠加,提升了机器人的环境适应性。研究结果为后续机器人系统的设计及工程应用提供了重要的理论依据。     

Semi-solid thixo casting structure of aluminum alloy and relevant assistant analysis with the help of computer simulation

The relationship between structure morphology of semi-solid aluminum alloy die-casting sample and filling condition was studied. By systematical structure analysis and computer simulation of the filling process, the quantitative relationship between microscopic morphology (such as solid fraction, grain size and shape) and formation state was studied. The results showed that the billet microstructure must have fine and round grains for the die-casting of complex shapes. It is necessary to optimize injection speeds to escape the non-uniform distribution of the solid fraction in complex and changeable mold cavity.     

Estimation of performance of a J-T refrigerators operating with nitrogen-hydrocarbon mixtures and a coiled tubes-in-tube heat exchanger

The exergy efficiency of Joule-Thomson (J-T) refrigerators operating with mixtures (MRC systems) strongly depends on the choice of refrigerant mixture and the performance of the heat exchanger used. Helically coiled, multiple tubes-in-tube heat exchangers with an effectiveness of over 96% are widely used in these types of systems. All the current studies focus only on the different heat transfer correlations and the uncertainty in predicting performance of the heat exchanger alone. The main focus of this work is to estimate the uncertainty in cooling capacity when the homogenous model is used by comparing the theoretical and experimental studies. The comparisons have been extended to some two-phase models present in the literature as well.Experiments have been carried out on a J-T refrigerator at a fixed heat load of 10 W with different nitrogen-hydrocarbon mixtures in the evaporator temperature range of 100–120 K. Different heat transfer models have been used to predict the temperature profiles as well as the cooling capacity of the refrigerator. The results show that the homogenous two-phase flow model is probably the most suitable model for rating the cooling capacity of a J-T refrigerator operating with nitrogen-hydrocarbon mixtures.     

新型金属冷吊顶辐射板的数值模拟与分析

分析现有辐射板的优缺点,设计新型辐射板的结构,并进行CFD模拟和流量优化分析,为辐射吊顶系统的研究和设计提出理论分析与建议。此新型辐射板使冷媒水与辐射板直接接触,大大减少了接触热阻,传热量明显增加。另外,其加工工艺简单,初投资减少。流量是影响换热量的主要因素,随着流量的增加,板面温度分布更均匀,制冷量增加,达到紊流后,增加幅度变缓。该新型辐射板经济流量为1m3/h,此时换热量和能耗等指标达到最优。     

一种六自由度上肢康复机器人的结构设计及运动学分析

为解决现有上肢康复机器人功能单一以及结构复杂的问题,提出了一种6-DOF外骨骼式上肢康复机器人,建立了康复机器人的运动学模型,通过D H变换对其正向运动学和逆向运动学进行求解.运用Pro/E对康复机器人进行三维建模,通过Mechanism/Pro导入ADAMS/view中进行运动学仿真,得到机器人末端位移的仿真曲线和理论曲线一致,验证了理论推导的正确性,进一步仿真结果证明该方案具有较好的运动特性.     

一种平地楼梯两用助行机器人的建模与仿真分析

为解决老年人和残疾人出行不便的问题,提出了一种平地楼梯两用的助行机器人设计方案,采用轮足式结构实现爬楼梯功能.用R.Morales方法进行正、逆运动学分析,计算出机器人质心及各关节位移轨迹.用RobersonWittenburg方法推导出系统的动力学方程,将逆运动学解代入动力学模型中求得各关节所需的驱动力矩.同时在ADAMS中建立虚拟样机模型,进行运动学和动力学仿真,得到的机器人质心位移轨迹和各关节驱动力矩与MATLAB的计算结果一致,验证了设计方案的可行性和理论推导的正确性.