基于虚拟现实和仿生算法的装配序列优化

针对自动装配规划和交互式规划都存在不足,将虚拟现实和仿生算法结合起来,提出一种生成优化装配序列的新方法.建立基于几何约束的虚拟装配环境,在该环境中根据经验和知识进行交互式拆卸,定义优先约束表来表达零件间的优先约束关系.应用蚁群算法规划出初始优化的装配顺序,再在虚拟环境下进行仿真、评价和优化,考虑装配位置可达性和工具操作等因素,识别新的优先约束和评价准则,重新规划出更优的装配顺序,不断反复和完善,直到得到满意的最佳装配顺序为止.通过实例验证该方法有效性.     

A converse method-based approach for assembly sequence planning with assembly tool

In order to improve the quality and efficiency of assembly sequence planning for complex mechanical product, a converse method-based approach for assembly sequence planning is proposed. Firstly, the disassembly interference matrix of product and the disassembly constraint degree of part are defined. Product disassembly sequence is obtained through geometry reasoning algorithm and the searching work of disassembly sequence is simplified by the contact constraint set. Secondly, the maneuverability of tool is inspected through the using matrix and interference matrix of assembly tool. The infeasible disassembly sequence is excluded and product assembly sequence is obtained by reversing the order of disassembly sequence. Thirdly, the evaluation mechanism for assembly sequence is established to get the optimal assembly sequence and the optimal assembly sequence is selected by calculating the value of evaluation function. Finally, a vibration generator is illustrated to verify the validity and feasibility of the proposed approach.     

Mechanical Product Disassembly Sequence and Path Planning Based on Knowledge and Geometric Reasoning

A feature-based assembly model is proposed for disassembly sequence planning, and establishing a correct and practical disassembly path for the part in the product, based on geometric reasoning and knowledge. The fundamental assembly modelling strategy for a product is based on the mating features of its parts. An algorithm is introduced which uses the information provided by the mating features of parts in the product to find the candidate parts for disassembly and to carry out disassembly path planning. A complete and accurate interference checking approach is used to ensure no global collision while disassembling a part. In some cases, it cannot be implemented by geometric reasoning alone, so a set of criteria and heuristic rules based on knowledge, constraints, relationships among parts, and quantitative disassemblability assessment are used. It can also be carried out interactively by the user when necessary. The proposed method is integrated with the CAD model of the product. The user can visually disassemble the product while planning, so it is easier to carry out the disassembly planning and generate an optimal sequence.     

A novel approach to the geometric feasibility analysis for fast assembly tool reasoning

A product assembly or disassembly is completed by means of proper tools. The selection of feasible tools is an important process in planning a complete assembly or disassembly sequence. A key tooling consideration in assembly or disassembly planning is to reason the available space for a tool application during the assembly or disassembly of a product. Currently, assembly tool reasoning about space mainly depends on simulation-based or user-interactive approaches because of its computational complexity. These approaches are inappropriate in dealing with various what-if scenarios regarding assembly or disassembly planning in a rapid product development. They also depend on users’ expertise or experience in assembly or disassembly. This paper presents a novel approach to the geometric feasibility analysis for fast assembly tool reasoning. Techniques described in this paper are advantageous not only in the aid of generating a complete assembly or disassembly plan but also in the efficient support of such systems as computer-aided assembly planning (CAAP), design for manufacturing (DFM), design for assembly (DFA), design for disassembly (DFD), and computer-aided tool selection (CATS).     

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.     

Integrated assembly and machining planning for electronic products using a genetic algorithm approach

To produce an electronic product, both assembly operations and machining operations are required in the process plan. In most cases, the assembly operations and machining operations need to be combined in a continued order with an integrated sequence. This is different from the traditional process planning approaches in which machining operations and assembly operations are separated as two independent tasks with no interactions. For an electronic product, the two types of operations and the associated costs may affect each other in an interactive way. Therefore, the sequence planning of assembly operations and machining operations must be analyzed with an integrated model. In this research, a graph-based model is presented to represent the assembly and machining operations in an integrated model. The related operation cost functions are developed to evaluate the costs for the integrated assembly and machining sequences. The integrated sequence planning problem is solved using a genetic algorithm approach with an objective of lowest operation costs. As a result, the assembly operations and machining operations can be planned in an integrated sequence suitable for producing electronic products. The result shows that the developed method using the genetic algorithm approach is efficient for solving the integrated sequence planning problem. Example products are demonstrated and discussed.     

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.     

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.     

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。     

基于工程语义信息的拆卸序列规划算法研究

为了解决拆卸序列规划理论算法存在的求解空间过大的问题,提出一种基于工程语义信息的规划算法.该算法借助装配约束条件、拆卸干涉状况等工程信息,实施产品拆卸顺序生成和路径推理,直接排除从工程角度不可能的拆卸序列,达到缩减求解空间的目的.保证了算法同工程实际的一致性,提高了其实际应用和软件编程能力.     

基于不确定规划的产品拆卸序列规划

分析了产品拆卸序列规划中的不确定性,在基于混合图的产品拆卸模型的基础上,将产品拆卸序列规划转化为一类不确定规划问题。以机会约束规划模型为基础,使用模拟退火算法,给出了基于不确定规划的产品拆卸序列规划求解流程和算法。最后,通过一个简化的计算机主机箱实例说明了方法的有效性及优越性。     

基于知识的智能装配规划系统

为了保证装配工艺的合理性和实用性,提出了基于知识的智能装配规划方法。该方法利用联接件装配工艺的特点和知识,进行装配序列规划,建立了基于联接件知识的装配实例库,生成装配序列的途径有典型实例的匹配、标准实例的匹配和运用有向联接件知识的装配序列规划。为了使产品的装配周期最短,并提高装配系统的柔性和可靠性,提出了基于多代理的装配任务规划方法,该方法综合考虑了装配操作时间和装配工具变换时间等因素。     

Disassembly sequence planning approach for product virtual maintenance based on improved max–min ant system

In order to realize automation and intelligence of product disassembly process in a virtual maintenance environment, an improved max–min ant system based methodology for product disassembly sequence planning was proposed. The feasibility graph for product disassembly process was defined and the mathematic model of product disassembly sequence planning problem was set up. Thus, the problem of product disassembly sequence planning was transformed into the problem of searching optimal path on a feasibility graph. Moreover, an improved max–min ant system based on the strategy of sorting elite ants was presented and the flowchart of the improved algorithm was designed. Finally, by simulation examples, the robustness and outperforming others of the improved algorithm were verified.     

面向产品回收设计的拆卸序列规划

基于绿色产品设计的思想，定义了产品的层次化结构模型，对产品的拆卸进行了建模分析，并主要讨论了拆卸序列组合爆炸、零部件邻接矩阵、拆卸算法等关键问题，实现了产品回收与再设计的拆卸序列规划。     

Disassembly modeling, planning, and leveling for a cam-operated rotary switch assembly: a case study

The manufacturing organizations have been witnessing a paradigm shift on designing products and services from manufacturing to sustainability. Product disassembly is a vital strategy for industrial recycling and remanufacturing which generates the desired parts and/or subassemblies by means of separation of a product into its elements. This article presents the appropriate methods for modeling planning and leveling the disassembly process of a cam-operated rotary switch assembly. The methodology involves disassembly modeling using a graphical approach. Disassembly process planning has been done using reverse assembly approach. Disassembly leveling has been done to maintain profitability and environmental features at a desired level. An optimal disassembly sequence has been derived using disassembly leveling. The resultant cost of disassembly for reusable components has been computed. The article presents a unique contribution to the field of designing for disassembly from the perspective of rotary switches.     

Optimization of disassembly sequence planning for preventive maintenance

Disassembly sequence planning is considered an important research topic in the manufacturing automation field. In recent years, in close collaboration with manufacturers, many investigations have been conducted to design robust and profitable dismantling systems. Therefore, the designers of new products have to consider the disassembly constraints in the design phase of products. Moreover, considering the disassembly constraints is important not only in the context of life end of a product but also in its life cycle in order to reduce problems related to its exploitation and maintenance. Consequently, the optimization of the disassembly process of a product is a crucial task for improving the product design. This article presented an automated disassembly sequence planning approach based on ant colony algorithm. The developed method permits the generation of an optimal and feasible disassembly sequence planning of a product from its computer-aided design (CAD) model. Several criteria were introduced in this approach such as part volume, tool change, disassembly directions, and the maintainability of wearing part. A comparison between genetic and ant colony algorithms was conducted to reveal the effectiveness of the proposed approach. A case study is presented and an implemented tool was developed. The obtained results demonstrate the satisfactory side of the considered criterions to identify the feasible disassembly sequence plan.     

Product cooperative disassembly sequence planning based on branch-and-bound algorithm

This paper focuses on the cooperative disassembly sequence planning (CDSP) problem which is essential to disassembly a large and complex product in practice. A disassembly hybrid graph model (DHGM) is constructed to describe the mating contact and noncontact priority relationships among constituting product components. Thus, the disassemblability constraint expression can be deduced from it by reasoning. The CDSP is different from the disassembly sequence planning except for they are NP-complete. Therefore, a novel method is presented to generate cooperative disassembly hierarchical tree (CDHT) from the DHGM based on branch-and-bound algorithm in which two user-defined variables are introduced to control the size of the CDHT .The optimal solutions with a minimal disassembly time are derived according to the objection function. Finally, an example illustrates the proposed method.     

基于改进人工蜂群算法的产品拆卸序列规划

为了提高复杂产品拆卸序列规划效率,提出了一种改进的人工蜂群算法用于此类问题求解。通过拆卸混合图表达产品零部件之间的连接关系和优先约束关系,并推导出可行拆卸序列的约束表达式,建立拆卸序列规划数学模型和适应度计算公式。对初始种群进行了优先约束规划,提出一种可行度算法用于蜂群对蜜源的搜寻与选择。定义了自适应选择参数、动态平衡可行度与适应度算法的优先配比,以实现复杂产品拆卸序列规划的快速求解。最后以内啮合齿轮泵为实例,利用所提方法进行了拆卸序列规划求解,通过分析实验结果,并对比传统人工蜂群算法,证明了该方法的可行性和高效性。     

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。     

基于递归循环的层次化爆炸图自动生成方法

提出以递归循环和深度优先搜索层次化装配序列的策略自动生成复杂产品层次化爆炸图的方法。为使设计结构符合装配规划的要求,设计了可方便定义子装配体和编辑装配树的装配结构重构功能。为避免重复的干涉检测,研究干涉矩阵合成方法,通过对原始装配关系信息的整合,柔性化生成面向层次化结构的装配关系矩阵。为降低大规模序列规划问题的复杂性,将整体规划任务分解为若干个及若干层级子任务,子任务内采用多规则筛选算法,以基于干涉矩阵的几何可行性为前提,并行性、连续性、稳定性和方向性等为优化筛选指标,循环构建序列。提出递归爆炸算法,循环对层次化装配序列进行深度优先搜索,实时计算已爆炸零部件的累积包围盒,从而确定待爆炸零件位移矢量,自动生成间隔均匀有序、结构紧凑且空间层次感强的爆炸图。开发了基于Siemens NX的装配规划系统Auto Assem,以减速器及汽车部件实例验证了方法的有效性。