基于MSC Adams的新型离合器动态特性仿真

新型同步离合器的结构中,棘轮棘爪及中间件的啮合机构是最重要的部件. 利用Pro/E及MSC Adams建立该离合器的虚拟样机模型,并在MSC Adams中对离合器动态接合过程进行仿真,分析棘轮棘爪的碰撞特性,以及中间件的啮合特性. 所得结果对进一步研究该离合器动态接合过程的特性和设计有重要的指导意义.     

某履带车辆主离合器工作过程仿真

分析了某履带车辆主离合器结构及工作原理,用Pro／E软件对主离合器各部件进行了三维实体建模,建立了主离合器仿真流程图,基于ADAMS软件建立了主离合器的虚拟样机,并通过了模型验证。对履带车辆主离合器的接合、脱离和打滑的工作过程进行仿真,为进行履带车辆传动系统可靠性研究有重要意义。     

手动变速箱rattle噪声的仿真和试验

针对手动变速箱的振动和噪声直接影响整车NVH性能的问题,简述手动变速箱rattle噪声的产生机理,将非承载齿轮敲击过程理解为由离合器、承载齿轮、差速器和车身等组成的扭振系统和非承载齿轮副敲击系统相互作用的结果.用AMESim建立传动系统敲击模型并通过试验验证模型的准确性,重点分析离合器参数(刚度和迟滞阻尼)以及齿轮齿隙对齿轮敲击力的影响.结果表明,利用这些参数对变速箱rattle噪声加以控制可达到预期的效果.     

Fast and smooth clutch engagement control for dual-clutch transmissions

Automotive dual-clutch transmissions use two gear shafts and two clutches to perform automated gear shifts at a high comfort level. The two objectives of the clutch engagement controller are to realize a fast clutch engagement to reduce the gear shifting time, and a smooth clutch engagement to accurately track the demanded torque without a noticeable torque dip. This research work presents a new controller design that explicitly separates the control laws for each objective by introducing clutch engagement phases. Simulations and experiments in a test vehicle show that the control objectives are realized with a robust and relatively simple controller.     

Hybrid automata for linearizing the model of high-pressure thawing

The heat transfer phenomena concerned during thawing usually lead to non-linear distributed parameter systems, due to the existence of water phase change. When pressure changes, the thermodynamic effects make this model more complex. Hybrid automata allow continuous and discrete dynamics to be combined in the same method. Applied to our process, they allow a linear model to be obtained, and conserve its linearity when pressure changes are taken into account. The discrete events considered here are ice/water transitions and pressure changes. The continuous part of the model is heat transfer, either in solid, liquid or melting state of water.     

基于机器视觉的汽车精密零件缺陷检测

本文针对汽车精密零件外观质量检测的需求,利用机器视觉系统采集零件外观图像,建立数据平台。基于中值滤波和图像复杂度,提出了改进OTSU算法提取图像的外观缺陷特征,与样本库进行对比,以识别可能的外观缺陷,提高缺陷检测效率。并且,针对缺陷类型分析其影响因素,从而找到产生缺陷的原因,为零件加工过程的改善提供理论依据。同时,搭建了缺陷视觉检测平台,以汽车转向器内部套筒为对象,实现了精密零件外观缺陷在线缺陷检测。     

Dimensional precision simulation of the formed picture tube panel

In the forming process of picture tube panel, the accumulated residual stresses cause the formed part to shrink, and the thermal and mechanical loads cause the mold blocks to deform. These two factors result in large deviations on the dimensions of the formed panel, which are both modeled and simulated in this paper. For residual stresses analysis, a thermo-rheologically simple viscoelastic material model is introduced to consider the stresses relaxation effect and to describe the mechanical behavior according to the temperature change. The shrinkage of formed parts induced by the residual stresses is calculated based on the theory of shells, represented as an assembly of flat elements formed by combining the constant strain and the discrete Kirchhoff triangular elements. A thermoelastic model is presented to predict the deformation of the mold blocks during pressing, which is based on the steady mold temperature field and thermoelastic boundary element method. The integrated simulation results suggest the amounts that the mold cavity should be machined by, and have been verified by comparing the dimensional precision of the panels produced by the mold considering a uniform part shrinkage and mold expansion or the mold considering the predicted ununiform part shrinkage and mold deformation.     

基于数值方法的内超环面齿轮齿廓离散建模

超环面行星蜗杆传动系统中的关键零件内超环面齿轮的齿面是一种复杂的 空间曲面。为了实现复杂曲面的数控加工和采用有限元方法对其进行接触分析时,能否获得 精确的内超环面齿轮的实体模型是解决问题的关键。本文针对内超环面齿轮数字化建模问 题,根据内超环面齿轮的数学模型,对其螺旋齿面进行网格划分,提出基于数值方法的内超 环面齿轮离散建模方法。该方法采用截平面蔟将内超环面齿轮模型离散成数据点云,从而获 得内超环面齿轮离散模型,为后期的复杂曲面插值重构提供了基础。     

An algorithm for CAD tolerancing integration: Generation of assembly configurations according to dimensional and geometrical tolerances

For several years, Digital Mock-Up (DMU) has been improved by the integration of many tools as Finite Element (FE) Analysis, Computer Aided Manufacturing (CAM), and Computer Aided Tolerancing (CAT) in the Computer Aided Design (CAD) model. In the geometrical model, the tolerances, which specify the requirements for the proper functioning of mechanical systems, are formally represented. The nominal modeling of the parts and assemblies does not allow the prediction of the tolerance impacts on the simulation results as the optimization of mechanical system assemblability. So, improving the CAD model to be closer to the realistic model is a necessity to verify and validate the mechanical system assemblability. This paper proposes a new approach to integrate the tolerances in CAD model by the determination of the configurations with defects of a CAD part, used in a mechanical system. The realistic parts are computed according to the dimensional and geometrical tolerances. This approach provides an assembly result closer to the real assembly of the mechanical system. The Replacement of the nominal parts by the realistic ones requires the redefinition of the initially defined assembly mating constraints. The update of the mating constraints is performed by respecting an Objective Function of the Assembly (OFA). Integrating tolerances in CAD allows the visualization and simulation of the mechanical assemblies’ behavior in their real configuration and the detection of possible interference and collision effects between parts which are undetectable in the nominal state.     

复杂空间曲面零件实体造型研究

将机械零件加工方法引入ＡｕｔｏＣＡＤ实体造型中,模仿机械加工方法,用ＡｕｔｏＬＩＳＰ编写ＡｕｔｏＣＡＤ实体造型驱动程序,实现了空间圆柱凸轮、弧面分离凸轮,蜗形凸等复杂空间曲 体图的状速,准确绘制。     

车辆系统集成化建模与换档规律特性仿真

将传动系统的虚拟样机模型与操纵控制系统的模型集成起来,实现对包括发动机、液力变矩直至行动系统在内的换档动态特性的仿真,建立换档规律、液压控制系统、动力传动系统及行动系统的集成化模型,并在虚拟样机及控制软件中实现多学科多软件的联合仿真,在对车辆的32 km/h加速性能的仿真试验中,得到相应的仿真时间以及相关动力传动系统的动态特性.     

Structural optimization of as-built parts using reverse engineering and evolution strategies

In industry, some parts are prone to failures or their design is simply sub-optimal. In those critical situations, one would like to be able to make changes to the part, making it lighter or improving its mechanical resistance. The problem of as-built parts is that the original computer-aided design (CAD) model is not available or is lost. To optimize them, a reverse engineering process is necessary to capture the shape and topology of the original design. This paper describes how to capture the original design geometry using a semi-automated reverse engineering process based on measurement provided by an optical 3D sensor. Following this reverse engineering process, a Fixed Grid Finite Element method and evolutionary algorithms are used to find the optimum shape that will minimize stress and weight. Several examples of industrial parts are presented. These examples show the advantages and disadvantages of the proposed method in an industrial scenario. Presented at the 7th World Congress on Computational Mechanics, Los Angeles 2006.     

Modeling and control of impact in mechanical systems: theory andexperimental results

Considers the equations of motion of mechanical systems subject to inequality constraints, which can be obtained by looking for the stationary value of the action integral. Two different methods are used to take into account the inequality constraints in the computation of the stationary value of the action integral: the Valentine variables method and the penalty functions method. The equations of motion resulting from the application of the Valentine variables method, which introduces the concept of “nonsmooth” impacts, constitute the exact model of the constrained mechanical system; such a model is suitable to be employed when the impacting parts of the actual mechanical system are very stiff. The equations of motion resulting from the application of the penalty functions method, which introduces the concept of “smooth impacts,” constitute an approximate model of the constrained mechanical system; such a model is suitable to be employed when the impacting parts of the actual mechanical system show some flexibility. Various feedback control laws from the natural outputs and from their time derivatives are studied with reference to both models of impact; the closed-loop systems resulting from the application of the same control law to both models show pretty much the same global asymptotic stability properties. The proposed control laws are only concerned with regulation problems in the presence of possible contacts and impacts among parts of the mechanical system or with the external environment. The effectiveness of the proposed control structure has been tested experimentally with reference to a single-link robot arm, showing a valuable behavior     

CAD based model of ultrasonic shot peening for complex industrial parts

This paper presents a numerical model developed specifically for ultrasonic shot peening (USP). It allows simulating the shot dynamics (trajectories in the chamber and impacts on the peened sample) in industrial configurations. The model supports complex 3D geometries, rotating parts and employs efficient collision detection algorithms for short computation times. The aim is to improve peening chamber designs and the choice of process parameters. The algorithm and main assumptions are presented. Numerical studies are then conducted to determine the performances of the model, in terms of computation time. Finally, a case study on a spur gear tests the model in an industrial configuration and shows a high correlation between the numerical results and experimental data.     

Analysis of Hybrid Systems Based on Hybrid Net Condition/Event System Model

In thispaper, hybrid net condition /event systems are introducedas a model for hybrid systems. The model consists of a discretetimed Petri net and a continuous Petri net which interact eachother through condition and event signals. By introducing timeddiscrete places in the model, timing constraints in hybrid systemscan be easily described. For a class of hybrid systems that canbe described as linear hybrid net condition /eventsystems whose continuous part is a constant continuous Petrinet, two methods are developed for their state reachability analysis.One is the predicate-transformation method, which is an extensionof a state reachability analysis method for linear hybrid automata.The other is the path-based method, which enumerates all possiblefiring seqenences of discrete transitions and verifies if a givenset of states can be reached from another set by firing a sequenceof discrete transitions. The verification is performed by solvinga constraint satisfaction problem. A technique that adds additionalconstraints to the problem when a discrete state is revisitedalong the sequence is developed and used to prevent the methodfrom infinite enumeration. These methods provide a basis foralgorithmic analysis of this class of hybrid systems.     

An integrated approach of reverse engineering aided remanufacturing process for worn components

The worn mechanical components/parts arrived in the remanufacturing system exhibit highly uncontrolled variabilities in failure conditions as well as structures and shape complexities. With the aid of reverse engineering (RE) technologies, a quick and accurate acquisition of the damaged areas of the worn part is attainable and thereby facilitates remanufacturing operations necessary to bring the parts back to like-new conditions. In this paper, a reverse engineering based approach is proposed to aid the remanufacturing processes of worn parts. The proposed approach integrates 3D surface data collection, nominal model reconstruction, fine registration, extraction of additive/subtractive repair, tool path generation and actual machining process, seeking to improve the reliability and efficiency of manual repair process. For nominal model reconstruction, a Prominent Cross-Section algorithm embedded with curvature constraint is proposed to automatically identify the boundary of the part's damaged area and thereby eliminate the defective point clouds from the reconstruction process. With the nominal reconstruction model and the 3D model of the worn part, a modified ICP algorithm integrating curvature and distance constraints is proposed to achieve a best-fit position of the two models by automatically identifying and eliminating the unreliable corresponding pairs through iterations. The proposed approach is demonstrated through remanufacturing of two different mechanical components and is approved to be efficient and effective.     

基于Pro/E的远程零件参数化设计系统研究

提出了一种远程设计机械零部件的新方案.利用VC+ +对Pro/E进行二次开发,将开发的程序封装成COM组件,利用Pro/E进行参数化建模,通过ASP技术调用COM组件实现远程参数化设计.以斜齿圆柱齿轮为例说明机械零部件远程设计系统的实现过程.     

基于UG二次开发的参数化建模方法

对于目前有关UG二次开发中零件的常用参数化建模方法,论文提出了两种更为简单快速的建模方法.第一种方法是以内齿圈参数化设计为例,通过先建立零件的模板模型,然后在其对话框的回叫函数中,编写代码更改参数,最后更新,实现零件的参数化.第二种方法是以超声变幅杆为例,利用UG建模环境中的JA文件录制功能,将零件的建模过程进行录制,用得到的代码在对话框的回叫程序中替代原本用API或grip开发的零件建模程序,然后将对话框的输入值与代码中模型的参数进行关联,实现零件的参数化.这两种方法的应用能有效减少设计人员的重复劳动,提高设计效率.     

板材多点成形过程的非参数模型及自适应控制

研究了三维板类件的多点成形复杂的非线性过程。将影响成形精度的诸多因素看作系统扰动，成形过程简化为离散的单输入单输出系统，得到其非参数模型。在满足一定假设务件的前提下，多点成形过程可线性化为一个带有单参数的线性时变系统：通过对系统的分析，得到了多点成形过程的闭环递推自适应控制算法。仿真结果表明，在自适应算法的逐次控制下，工件形状以较快的速度收敛到设计的目标形状，实现了对板类件多点成形这一复杂过程的有效控制。     

A network-based assessment approach for change impacts on complex product

The complex product design is a continuously changing process from customer requirements to a maturity design. During this process a change of one part will, in most cases, causes changes in other parts and even the whole product. The assessment for the impacts of such changes can support designers’ designing and help manager to manage redesigning. A complex product can be considered as a weighted network of parts, subassemblies, or subsystems. Based on the theory of weighted networks, three changeability indices (degree-changeability, reach-changeability and between-changeability) are presented. Degree-changeability is used to calculate the direct change impacts. Reach-changeability is used to assess the indirectly change impacts because of propagation. If a part influences the other parts dramatically and it is also influenced by them, this part can be predicted by between-changeability. Finally, the three changeability indices are proven to be effective for the change impact assessment through a real-world case of Roots Blowers. With the analysis, the designers can avoid changing to “expensive” parts or subsystems.