增强现实诱导拆卸序列规划研究

装配体的拆卸序列规划研究对于增强现实维修诱导系统具有重要意义。为能以较高效率求解诱导拆卸装配体的序列方案,基于装配体中零件之间的干涉矩阵,提出并建立目标装配体的拆卸混合层次图模型。通过拆卸影响因子的分析,进一步得到装配体拆卸时间数学模型,并运用自适应遗传算法求解最优的拆卸路径。最后,通过增强现实诱导拆卸系统仿真实例,验证了此方法的可行性和准确性,为增强现实诱导拆装系统的进一步开发和改进奠定了基础。     

基于子装配识别的产品拆卸序列生成研究

对含有较多零件的复杂产品拆卸方法作了讨论,提出了一种基于子装配识别的拆卸序列生成算法。根据装配连接图和干涉图识别出子装配体,然后将子装配体看作一个零件,采用装配经验知识与几何推理相结合的方法生成子装配体序列,最后以一个装配实例说明了算法的有效性。     

面向机械零件设计的可选择性拆卸策略研究

机械零件可选择性拆卸规划能够实现从一个装配体上拆除一个或几个零件,这对于产品维修、报废处理和回收利用是非常有用的。尽管完全拆卸规划算法也能得到可行的拆卸序列,但由于完全拆卸规划方法需要将装配体的所有零件都进行拆卸,通过适当的分析和评价也能找到所需的可行拆卸序列,但这是非常困难的,特别当零件数量较多时,通常得不到最优解。本文在建立广义的机械零件CAD模型的基础上,定义了装配体中的拆卸波是装配体中某些零件的一种拓扑关系,可反映零件之间的拆卸顺序。并在此基础上提出了一种基于拆卸波的零件可选择性拆卸规划算法。该算法的计算量小,容易用它来进行高效的搜索,获得最优的零件可选择性拆卸序列。     

一种基于运动规划的选择拆卸序列规划技术

选择拆卸序列规划是产品维修或回收的重要环节,针对目前选择拆卸序列规划算法中自动化程度较低的问题,提出一种基于运动规划的选择拆卸序列规划方法。该方法首先根据复杂产品中零件数量繁多,形状不规则的特点,采用基于自适应动态多树的快速扩展随机树(Rapidly-exploring random tree,RRT)算法对零件进行运动规划。在此基础之上,通过对装配体进行自动分层处理,分析零件间拆卸约束关系,构建装配体的拆卸约束关系图。最后通过对拆卸约束关系图的分析处理,获得目标零件的选择拆卸序列。以某底盘的目标零件为例,对提出的算法进行了验证。     

基于工程语义的虚拟装配序列规划

传统的装配序列规划主要从几何和约束角度考虑,忽略了装配过程中的工程可行性因素,导致自动化的装配序列推理方式可能产生不可行解。对装配特征进行深入分析,构建面向拆卸的全语义模型,在保证拆卸过程几何可行性的基础上,求解装配体的装配序列,解决了装配序列工程可行性问题。通过引入距离语义的概念,解决拆卸过程中狭小空间与自由干涉矩阵的冲突问题;通过引入结构语义的概念,解决零件的拆卸顺序的问题,并将语义从约束层次上升至结构层次。     

面向多人同时作业的拆卸序列规划

为生成面向多人同时作业的并行拆卸序列、提高求解的效率与质量,在分析现有方法不足之处的基础上,提出基于改进蚁群算法的面向多人同时作业的拆卸序列规划方法(Disassembly Sequence Planning For Multipeople Simultaneous Operation,DSPMSO)。针对该方法的特点,基于零件分层图对于零件配合关系以及可拆卸性的表达,提出改进的蚂蚁搜索方式,并采用动态候选表避免无效序列的产生;定义了零件拆卸所需人数与拆卸等待时间,提出以考虑等待时间为主的多人拆卸成本模型;针对基本蚁群算法求解复杂装配体拆卸序列时算法求解效率与解的质量难以兼顾的问题,提出算法的分阶段迭代策略:根据路径信息量确定算法迭代阶段,使蚂蚁具有不同的选路策略,提出与之对应的蚂蚁信息素自适应更新机制,使算法在求解的效率与质量之间取得较好的平衡。通过实例对关键参数的取值进行讨论,并验证了算法各项优化措施的有效性。     

基于Pareto解集蚁群算法的拆卸序列规划

为提高产品拆卸序列规划的效率,分析拆卸序列规划问题中的多个优化目标平衡问题,提出一种基于Pareto解集的多目标蚁群优化算法求解此类拆卸规划问题,并给出拆卸序列的构建过程。通过利用拆卸矩阵推导拆卸可行条件,获得可以执行拆卸操作的零件及其可行的拆卸方向。通过利用零件的轴向包围盒(Axis aligned bounding boxes,AABB)计算零件的拆卸行程。考虑拆卸方向改变次数、拆卸总行程、拆卸零件数量为优化目标,通过利用蚁群算法搜索可行解并计算各个解之间的支配关系,得到Pareto解集,实现求解优化的拆卸序列,给出算法的具体步骤。最后以单杠发动机为拆卸实例,利用所提方法进行拆卸序列规划求解,通过分析试验结果,并对比典型的单目标蚁群规划算法,证明了该方法的高效性和可行性。     

自动生成优化的拆卸序列的初始群体

研究废弃产品的拆卸序列问题。首先，提出建立装配体的干涉一自由矩阵，描述零件相互之间的空间关系。然后，提出一种新的计算模型，据此计算各个零件从装配体上可以拆卸下来的方向，从而确定拆卸序列在几何上的可行性。最后，提出自动生成优化的拆卸序列的初始群体的计算方法，从而有效地提高遗传计算最优装配体拆卸序列的搜索效率。通过一系列的实例验证，证明了提出的这套方法切实可行。     

基于结构模型的拆卸序列规划研究

为了解决装配结构复杂的产品拆卸序列规划中因数据组合爆炸而导致运算量剧增的问题,首先分析了典型装配体的拆卸特点,以零件自由度交集的运算结果作为拆卸方向的判断依据,提出了约束消除的概念,进而通过启发式算法实现了拆卸序列的自动生成;为了提高拆卸序列规划的运算效率和计算结果的实用性,引入了以装配关系为基础的层次化结构模型,通过逐层分解的方法降低了装配结构深度,避免了从整个复杂装配体上求单一零件的拆卸序列,达到了减少运算的目的;最后以简化的汽车为例,阐述了基于结构模型的拆卸序列规划过程。研究结果表明,以层次化结构模型为基础、以约束消除为原则的拆卸序列规划能有效降低运算量,从而控制复杂产品的数据组合爆炸问题。     

基于零件约束的装配规划技术研究

装配规划是虚拟装配中的关键技术。这里将装配序列的分层规划方法和拆卸法求解装配序列的方法相结合，在研究产品装配层次结构的基础上，以子装配体为研究对象，利用零件之间的装配约束信息求解零件的拆卸方向和顺序，进而实现产品的装配顺序和路径规划。     

A green assembly sequence planning model with a closed-loop assembly and disassembly sequence planning using a particle swarm optimization method

In a green product life cycle, it is necessary to determine how to disassemble a product before the product is planned to be assembled. In this research, a green assembly sequence planning model is developed. A closed-loop assembly sequence planning model is presented by integrating assembly and disassembly sequence planning models. For an assembled product, an assembly sequence planning model is required for assembling the product at the start, while a disassembly sequence planning model is performed for disassembling the product at the end. In typical assembly and disassembly sequence planning approaches, the two sequences are independently planned and evaluated. In this paper, a closed-loop model is presented to concurrently generate and evaluate the assembly and disassembly sequences. First, a graph-based model is presented for representing the feasible assembly sequences and disassembly sequences. Next, a particle swarm optimization (PSO) method with a new encoding scheme is presented. In the PSO method, the assembly and disassembly sequences can be simultaneously represented and evaluated with an objective of minimizing the total of assembly costs and disassembly costs. The test results show that the presented method is feasible and efficient for solving the integrated assembly and disassembly sequence planning problem. An example product is illustrated and discussed.     

Assembly sequences merging based on assembly unit partitioning

Assembly sequence planning is a typical of combinatorial optimization problem which is difficult to be tackled when the number of parts of assembly becomes large. To reduce the searching space of assembly sequence planning of complex products, assembly sequences merging based on assembly unit partitioning is suggested. Assembly unit partitioning is presented to decompose the complex products into a group of assembly units containing a reduced number of parts or components, and the assembly design constraints and the assembly process constraints are comprehensively taken into account. The global optimal assembly sequences can be acquired through three steps. Firstly, the assembly units and decision graph of assembly unit are generated utilizing fuzzy analytical hierarchy process approach. Secondly, the optimal or near-optimal subsequences of assembly units can be obtained with current efficient methods of assembly sequence planning. Thirdly, under the assembly interference of assembly relations (geometrical constraints) of the whole products and the assembly precedence concluded by subsequences of assembly units, the assembly sequence merging is implemented to generate the global assembly sequences, and the optimal sequence is obtained through assembly sequences evaluation. The assembly constraints considered at the two previous steps is represented by the evaluation function. The effectiveness of the method is verified by an illustrative example and the results show that the searching space of assembly sequence merging of complex products is reduced remarkably and the optimal assembly sequence of the whole produces is obtained.     

基于图集的机械结构部件信息建模

提出图集表达方式的机械结构部件信息建模方法，它由拓扑关系属性图，连接件约束图，特殊工艺过程约束图和公差图组成，该方法不仅可以全面，直观地表达工艺设计所需要的信息，而且非常便于在装配工艺设计是使用。     

An Intelligent Computer-Aided Assembly Process Planning System

This paper presents an intelligent computer-aided assembly process planning system (ICAAPP) developed for generating an optimal assembly sequence for mechanical parts. The system employs a graph set technique for creating an assembly model. The set includes an attributed topological graph, an attachment constraint graph, a tolerance graph and a special process constraint graph. In the generation of assembly sequences for any product, the critical problems to be addressed include determining the base part, selection of subassemblies, defining all necessary constraints, and quantifying and solving these constraints. In the ICAAPP system, algorithms have been developed for the selection of the base part, defining of the subassemblies, and determination of the constraint values. A simple mechanical assembly is used to illustrate the feasibility of the proposed algorithms.     

基于贪婪算法的产品拆卸序列规划

分析了产品实际拆卸过程中的不确定性,将实际产品拆卸序列规划转化为一类贪婪算法求解问题。以最少工具更换次数为指标,构建了基于贪婪算法的产品拆卸序列规划调整的贪婪准则,进而给出了产品拆卸序列规划调整流程。最后,通过一个简化的计算机主机箱的拆卸说明该方法的可行性和有效性。     

Subassembly identification for assembly sequence planning

Assembly sequence planning is a typical of NP-complete problem which will spend a large amount of computation time or disk memory once the assembly becomes complex. The complex product or assembly is composed of many parts and the number of assembly relationships between them is numerous. To decrease the difficulty of assembly sequence planning of complex products, the subassembly identification methods are focused on. It aims to decompose a complex assembly into a limitative number of subassemblies. Each subassembly contains a relatively smaller number of parts and the assembly sequence planning tasks of them can be handled efficiently. The subassembly identification methods for assembly sequence planning are summarized with respect to assembly constraints. The assembly constraints including the topological, geometrical, and process constraints are considered and merged into the assembly models for subassembly identification. The assembly models are generally represented as directed or undirected assembly diagrams including these considered constraints. It is generally taken as the input information to generate appropriate subassemblies complying with the requirements. The graph theories and graph search algorithms, integer programming methods and the emerging techniques, such as the knowledge-based methods, the intelligent algorithms and the virtual technology, etc. are advocated to resolve the subassembly identification problem with respect to the assembly models. The hierarchical assembly tree is widely used to represent the results of subassembly identification. These useful methods are not only used to subassembly identification for assembly sequence planning, but also successfully referred to by product disassembly.     

Unification of the a priori inconsistencies checking among assembly constraints in assembly sequence planning

Sequence planning generation is an important problem in assembly line design. A good assembly sequence can help to reduce the cost and time of the manufacturing process. This paper focuses on assembly sequence planning (ASP) known as a hard combinatorial optimization problem. Although the ASP problem has been tackled via even more sophisticated optimization techniques, these techniques are often inefficient for proposing feasible assembly sequences that satisfy the assembly planners’ preferences. This paper presents an approach that makes easier to check the validity of operations in assembly process. It is based on a model of the assembly planners’ preferences by means of strategic constraints. It helps to check a priori the consistency of the assembly constraints (strategic and operative constraints) given by the assembly system designers before and while running an assembly plan generation algorithm. This approach reduces the solution space significantly. A case study is presented to demonstrate the relevance of the proposed approach.     

装配关系的有向图表达方法研究

产品的装配关系表达方法直接关系到计算机辅助装配规划的方法与效率，分析了已有的装配关系表达方法，提出了有向装配连接图概念，有向装配连接图能够将建模的过程信息保存在有向边中，从而有割集分解方法进行装配序列规划提供更多信息。通过将装配建模配合关系建立过程转换成图的有向边表示，给出有向装配连接图的构造方法，在证明有向装配连接图相关性质基础上，给出在Unigraphics系统实现有向装配连接图算法。     

复杂环境下的装配路径求解与优化

针对三维复杂环境下的装配路径规划问题,运用栅格法建立了规划空间模型,基于蚁群算法求解出了一条避开障碍物的初始路径;对求解得到的装配初始路径,提出采用二分法插值优化方法缩短装配路径长度,在规划过程中采用目标零件与障碍物的轴向包围盒进行避障。对装配路径的求解及优化进行了实例测试,获得了一条无碰撞的最短的平滑路径,验证了算法的有效性和可行性。     

An effective integration approach toward assembly sequence planning and evaluation

An integration strategy for assembly sequence planning and sequence scheme evaluation is proposed. This strategy can be used to plan a reasonable assembly sequence, to optimize a sequence scheme, and to predict whether a collision will occur between the assembly tool and assembled components by considering factors like target components and assembly resources. A hybrid method is presented for assembly sequence modeling that combines human-computer interactive operations to manually build a hierarchical assembly sequence main model and a hybrid graph method to automatically generate sub-assembly sequence schemes of the main model. An optimization algorithm based on time-cost is introduced to handle a best candidate components selection. This relieves the problem of limited capability found when handling large size assembly models with traditional methods. The essential issues involved in system implementation are discussed as well; these include a representation method for the assembly consequence model, an optimization model of assembly sequence planning, and an object-oriented system architecture model employed with multi-agent technology for visually evaluating the assembling process. This system, KM computer-aided assembly process planning, KMCAAPP, has been developed on the basis of our previous work, KMCAD3; KMCAAPP uses the presented approach. KMCAAPP can be integrated with CAD model from KMCAD3D. A case study shows that the presented approach can use large CAD assembly models and delivers a feasible and effective way to integrate the assembly sequence planning process with scheme evaluation by visually evaluating the assembling process. This allows the identification of design errors in a timely manner and mitigates economic loss.