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Kinematics Analysis of Mechanisms Based on Virtual Assembly

Chinese Journal of Mechanical Engineering 2010年第6期23卷 748-757页

作者： ZHANG Zhixian LIU Jianhua ning ruxin School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China

Currently, virtual assembly technology has attracted increasing attention due to considerations of solving assembly problems in virtual environment before actual assembly in manufactory. Previous studies on kinematic analysis of mechanism only aim at analyzing motion law of single mechanism, but can not simulate the multi-mechanisms motion process at the same time, let alone simulating the automatic assembly process of products in a whole assembly workshop. In order to simulate the assembly process of products in an assembly workshop and provide effective data for analyzing mechanical performance after finishing assembly simulation in virtual environment, this study investigates the kinematics analysis of mechanisms based on virtual assembly. Firstly, in view of the same function of the kinematic pairs and the assembly constraints on restricting the motion of components （subassembly or part）, the method of identifying kinematic pairs automatically based on assembly constraints is presented. The information of kinematic pairs can be obtained through calculating the constraint degree of the assembly constraints. Secondly, the incidence matrix eliminating element method is proposed in order to search the information and establish the models of mechanisms automatically after finishing assembly simulation in virtual environment. Both methods have important significance for reducing the workload of pretreatment and promoting the level of automation of kinematics analysis. Finally, the method of kinematics analysis of mechanisms is presented. Based on Descartes coordinates, three types of kinematics equations are formed. The parameters, like displacement, velocity, and acceleration, can be obtained by solving these equations. All these data are important to analyze mechanical performance. All the methods are implemented and validated in the prototype system virtual assembly process planning（VAPP）. The mechanism models are established and simulated in the VAPP system, and t

关键词： virtual assembly assembly constraint constraint degree eliminating element method kinematics equations,kinematics analysis

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Deformation Calculation of Cross-section Based on Virtual Force in Thin-walled Tube Bending Process

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Chinese Journal of Mechanical Engineering 2009年第5期22卷 696-701页

作者： LIU Jingyao TANG Chengtong ning ruxin School of Mechanical Engineering Beijing lnstitute of Technology Beijing 100081 China

Cross-section deformation is one of important factors affecting the quality of tube formation, and the tube＇s capability of transporting liquid and gas will be reduced because of the cross-section ellipse deformation due to the effect of shear load in plastic bending process. When the tube is bent, the extrados-wall bears the tension stress and the intrados-wall bears the compression stress, synchronously the cross-section is affected by the circumferential stress. According to the above, the distribution function and curve of tangential stress can be obtained according to force balance differential equations on circumferential direction and Trasca rule. Subsequently the real state and virtual state moment equations were established, a new method was presented adopting the virtual principle of deformation system to calculate the x-axis and y-axis displacement of arbitrary point on cross-section. So the major and minor axes of deformed cross-section can be calculated according to the displacements of each point, and the variety value of major and minor axes will be obtained further. Finally the theoretical calculating result is compared with NC tube rotary-bending experiment results to verify the rationality of theoretical analysis, and the cross-section deformation rule of thin-walled tube can be received.

关键词： thin-walled tube stress analysis major and minor axes cross-section deformation virtual force

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Computational Path Planner for Product Assembly in Complex Environments

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Chinese Journal of Mechanical Engineering 2013年第2期26卷 282-292页

作者： SHANG Wei LIU Jianhua ning ruxin LIU Mi School of Mechanical Engineering Beijing Institute of Technology

Assembly path planning is a crucial problem in assembly related design and manufacturing processes. Sampling based motion planning algorithms are used for computational assembly path planning. However, the performance of such algorithms may degrade much in environments with complex product structure, narrow passages or other challenging scenarios. A computational path planner for automatic assembly path planning in complex 3D environments is presented. The global planning process is divided into three phases based on the environment and specific algorithms are proposed and utilized in each phase to solve the challenging issues. A novel ray test based stochastic collision detection method is proposed to evaluate the intersection between two polyhedral objects. This method avoids fake collisions in conventional methods and degrades the geometric constraint when a part has to be removed with surface contact with other parts. A refined history based rapidly-exploring random tree （RRT） algorithm which bias the growth of the tree based on its planning history is proposed and employed in the planning phase where the path is simple but the space is highly constrained. A novel adaptive RRT algorithm is developed for the path planning problem with challenging scenarios and uncertain environment. With extending values assigned on each tree node and extending schemes applied, the tree can adapts its growth to explore complex environments more efficiently. Experiments on the key algorithms are carried out and comparisons are made between the conventional path planning algorithms and the presented ones. The comparing results show that based on the proposed algorithms, the path planner can compute assembly path in challenging complex environments more efficiently and with higher success. This research provides the references to the study of computational assembly path planning under complex environments.

关键词： assembly path planning motion planning stochastic collision detection rapidly-exploring random tree adaptive RRT

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Contact State Estimation Based on Surface-matching in Virtual Assembly

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Chinese Journal of Mechanical Engineering 2012年第1期25卷 1-11页

作者： HOU Weiwei LIU Jianhua ning ruxin SHI Jiancheng School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

Contact problems are one of the most challenging fields in virtual assembly. Information of contact states could be utilized to realize compliant motion of work pieces, to analyze the contact stress, to assist positioning parts and so on. Some methods have already been proposed to estimate contact states between objects and in most of these methods contact states between objects are simplified in order to realize real-time visual reality animation. While in virtual assembly contact states between parts are required to analyze contact stress, deformation and quality. Besides the contact state estimation method for virtual assembly should be able to handle a number of complex parts in real time. There are rarely known methods which could meet this requirement till now. In this study a contact state estimation algorithm based on surface-matching for virtual assembly is proposed. Contacts between parts are categorized into six basic types according to contact region of surfaces. Based on continuous collision detection of polyhedral models a novel contact state identification algorithm which is based on surface matching is proposed. Then contact evolution algorithm, which utilizes the extern force and contact information, is implemented to handle evolution of contact state. Finally a prototype system is developed to verify the above technologies. Experiment results reveal that contact state between parts could be estimated correctly in real time virtual assembly. The proposed contact state estimation algorithm provides a complete solution to obtain the contact state between parts in virtual assembly. Information of contact state between parts could be utilized to realize contact dynamic, contact stress analysis, assembly quality analysis, and so on.

关键词： virtual assembly contact state identification surface matching contact state evolution

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Layout Planning Technology of Cellular Manufacturing System Based on Process Interconnection Analysis

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Chinese Journal of Mechanical Engineering 2011年第6期24卷 1035-1044页

作者： CHEN Huawei WANG Aimin ning ruxin SHAO Canxia Digital Design and Manufacturing Laboratory Beijing Institute of TechnologyBeijing 100081China

With sustaining change of production mode,layout planning is no longer a thing built once for *** layout(CL) is becoming a hotspot in the research field of manufacturing system *** researches on layout planning are mainly concentrating on aspects of layout arithmetic,style and evaluation,*** seldom efforts are paid to CL and its specific problems as cell formation(CF),equipment sharing and CL *** problem analyzing of layout in cellular manufacturing system(CMS),research approach of cell formation,interactive layout and layout analysis threaded with process interconnection relationship(PIR) is *** key technologies in CL like CF technology based on similarity analysis of part processes,interactive visual layout technology,layout evaluation technology founded on PIR analysis and algorithm of cell equipment sharing are put *** the background of one enterprise which encounters problems of low utility of key equipments and disperse material logistic,an example of four-cell layout is *** CL adjustment and analysis results show that equipment with high level of sharing degree should be disposed around the boundary of its main cell,and be near to other sharing cells as possible; process route should be centralized by all means,so equipment adjustment is to be implemented along direction that route intersection can be decreased; giving consideration to the existence of discrete cell,logistic route and its density should be centralized to cells *** proposed research can help improve equipment utility and material logistic efficiency of CL,and can be popularized to other application availably.

关键词： cellular manufacturing system, layout planning process interconnection relationship cell formation equipment sharing interactive layout

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Integrated Virtual Assembly Process Planning System

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Chinese Journal of Mechanical Engineering 2009年第5期22卷 717-728页

作者： LIU Jianhua HOU Weiwei SHANG Wei ning ruxin School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China

Assembly process planning（APP） for complicated products is a time-consuming and difficult work with conventional method. Virtual assembly process planning（VAPP） provides engineers a new and efficiency way. Previous studies in VAPP are almost isolated and dispersive, and have not established a whole understanding and discussed key realization techniques of VAPP from a systemic and integrated view. The integrated virtual assembly process planning（IVAPP） system is a new virtual reality based engineering application, which offers engineers an efficient, intuitive, immersive and integrated method for assembly process planning in a virtual environment. Based on analysis the information integration requirement of VAPP, the architecture of IVAPP is proposed. Through the integrated structure, IVAPP system can realize information integration and workflow controlling. In order to mode/the assembly process in IVAPP, a hierarchical assembly task list（HATL） is presented, in which different assembly tasks for assembling different components are organized into a hierarchical list. A process-oriented automatic geometrical constraint recognition algorithm（AGCR） is proposed, so that geometrical constraints between components can be automatically recognized during the process of interactive assembling. At the same time, a progressive hierarchical reasoning（PHR） model is discussed. AGCR and PHR will greatly reduce the interactive workload. A discrete control node model（DCNM） for cable harness assembly planning in IVAPP is detailed. DCNM converts a cable harness into continuous flexed line segments connected by a series of section center points, and designs can realize cable harness planning through controlling those control nodes. Mechanical assemblies （such as transmission case and engine of automobile） are used to illustrate the feasibility of the proposed method and algorithms. The application of IVAPP system reveals advantages over the traditional assembly process planning method in

关键词： virtual assembly assembly model assembly task collision detection automatic constraint recognition cable harness assembly process planning

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Dynamic Simulation and Disturbance Torque Analyzing of Motional Cable Harness Based on Kirchhoff Rod Model

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Chinese Journal of Mechanical Engineering 2012年第2期25卷 346-354页

作者： WANG Chunsheng ning ruxin LIU Jianhua ZHAO Tao School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

The motional payloads on stabilized platform must be linked by some cable harnesses with other immobile *** the operation of stabilized platform,these cable harnesses can create spring disturbance torque which is exerted on the stabilized platform and then reduce the stabilizing *** of current studies can deal with the spring disturbance torque *** analyze the spring disturbance toque,a dynamic thin rod model is presented for simulating the motional cable harness which is based on the Kirchhoff rod theorem and can consider the geometrically non-linear *** internal bending and torsion restoring torques are simulated and then a predictive analysis of the disturbance torque can be performed in motional cable routing *** model is solved with differential quadrature method（DQM）.By using zeros of the Chebyshev polynomial as the grid points,the arc-coordinate is discretized to obtain a set of ordinary differential equations in time domain which is solved by implied method to obtain the profile and internal force of cable *** accuracy of this model is validated by comparing the simulation results and the experiment results（both the spring force and the deformed profile of the motional cable harness）.In the experiment,a special optical measuring instrument based on binocular vision is *** comparison of experimental and simulated results shows that the simulation model can represent the real motional cable harness well,and the spring disturbance force simulation results are precise enough for spring disturbance torque *** study will be helpful to obtain an optimized motional cable harness layout design with small spring disturbance torque.

关键词： motional cable harness simulation spring disturbance torque analysis Kirchhoff rod stabilized platform

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Integrated Manufacturing Cell Formation Technology Orienting Multi-product Type and Variant Volume Production

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Chinese Journal of Mechanical Engineering 2011年第1期24卷 12-22页

作者： CHEN Huawei WANG Aimin ning ruxin SHAO Canxia Digital Design and Manufacturing Laboratory Beijing Institute of Technology Beijing 100081 China

What is pursued by multi-product type and variant volume（MPTVV） production is rapid response and quick switching,so that structure of transferring line in manufacturing system is no longer *** formation（CF） algorithm is the key technology of cellular manufacturing system（CMS）.Currently,CF methods are mainly extended on the idea of group technology（GT） that covers a lot on analysis of resource capability matching and its *** constraints are considered,but seldom utilized *** to the problem of manufacturing cell（MC） formation under MPTVV production mode,integrated formation technologies for typical MC as group type of cell（GC）,flow type of cell（FC） and inherited cell（IC） are presented based on technical analysis of *** to practical production constraints like delivery time,product batch,equipment ability,key machine,key part and machine sharing,etc,an integrated formation model is constructed and internal interrelations of these constraints are analyzed ***,formation goals of types of MCs and their formation procedures under joint effect of formation constraints and rules are *** case study,three highly balanced GC are formed first;then FC formation are implemented based on the same data which indicate good balancing effect of cell load and flow-style production for key tasks;When task is adjusted,a new scheme is constructed on the result of FC configuration by using IC formation method,and more optimal performance of flow-style production is *** proposed comparative study of different type of cells strongly explains the validation of integrated MC formation in support of rapid manufacturing resource transformation under MPTVV production mode.

关键词： multi-product type and variant volume production cell formation flow style manufacturing cell inheriting manufacturing cell

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Physics-based Modeling and Simulation for Motional Cable Harness Design

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Chinese Journal of Mechanical Engineering 2014年第5期27卷 1075-1082页

作者： LIU Jianhua ZHAO Tao ning ruxin LIU Jiashun School of Mechanical Engineering Beijing Institute of Technology

The design work of motional cable in products is vital due to the difficulty in estimating the potential issues in current *** this paper,a physics-based modeling and simulation method for the motional cable harness design is *** model,based on continuum mechanics,is established by analyzing the force of microelement in *** the analysis procedure,three coordinate systems：inertial,Frenet and main-axis coordinate systems are *** variable substitution and dimensionless processing,the equation set is discretized by differential quadrature method and subsequently becomes an overdetermined nonlinear equation set with boundary conditions solved by Levenberg-Marquardt *** the profile of motional cable harness obtained from the integral of arithmetic solution,a motion simulation system based on＂path＂and＂profile＂as well as the experimental equipments is *** the same parameters as input for the simulation and the real cable harness correspondingly,the issue in designing,such as collision,can be easily found by the simulation *** research obtains a better result which has no potential collisions by redesign,and the proposed method can be used as an accurate and efficient way in motional cable harness design work.

关键词： motional cable harness physics-based modeling motion simulation Kirchhoff rod

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ENTERPRISE INTEGRATION PLATFORM BASED ON SERVICEORIENTED ARCHITECTURE

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Chinese Journal of Mechanical Engineering 2008年第3期21卷 36-40页

作者： MENG Xiaojun ZHANG Xu ning ruxin SONG Yu School of Mechanical and Vehicle Engineering Beijing Institute of Technology Beijing 100081 China Department of Scientific Research Taishan University Taian 271021 China School of Mechanical and Vehicle Engineenng Beijing Institute of Technology Beijing 100081 China

To achieve information integration, process integration and application integration of enterprise, an enterprise integration platform （EIP） based on service-oriented architecture （SOA） is built. The enterprise integration model depending on encapsulating the business processes as well as the enterprise applications by the neutral and standard web services is presented. The problem how to discover the existed enterprise resources and share them was resolved depending on the mechanism of publishing and discovering the services. The EIP is integrated closely with product lifecycle management （PLM） system so that the process integration as well as orchestration of the business process services is implemented by encapsulating the workflow engine of PLM system. Not only process integration and application integration, but also information integration based on the bill of material （BOM） conversion driven by process are achieved. Finally, an interpretive, qualitative case study on EIP is conducted for this research.

关键词： Enterprise integration platform (EIP) Service-oriented architecture (SOA) Information integration Process integration Application integration

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