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。     

Integrated knowledge-based assembly sequence planning

This paper presents a novel approach and system for the automatic generation, selection and evaluation, optimisation, and simulation of assembly plans. The information and knowledge about a product and its assembly (e.g. assembly constraints, solid model and CAD database, heuristic rules) are described using a hybrid approach and model with numeric and symbolic representation. A new methodology is presented to generate all feasible assembly sequences of the product by reasoning and decomposing the feasible subassemblies, and representing them by the assembly Petri net modelling. Qualitative strategic constraints are then used to evaluate the feasible assembly sequences. In order to obtain a good assembly sequence, some quantitative criteria such as assembly time and cost, workstation number, operator number, and part priority index are applied to select the optimal assembly sequence. Based on DFA analysis, MTM time analysis, and assemblability analysis, estimates are made of the assembly time and cost of the product when each of these sequences is used. A knowledge-based system KAPSS has been developed to achieve the integration of generation, selection evaluation, and visualisation of the assembly sequences.     

粒子群算法在装配顺序规划中的应用

装配顺序规划是计算机辅助工艺设计的一个重要环节,影响着轿车车身的装配质量和效率.针对当前装配顺序规划易产生组合爆炸等问题,提出了基于粒子群算法的装配顺序规划算法.装配偏差是影响装配质量的重要因素,因此应用装配体的装配偏差评价装配顺序.在装配顺序规划过程中,首先将装配顺序编码为粒子,根据所建立的判断规则进行识别粒子的可行性,并通过装配偏差评估可行粒子的适应度值,然后根据粒子群算法过程规划装配顺序,最后采用前翼子板案例阐述装配顺序的生成和优化过程.     

装配工艺规划中装配序列生成与评价方法研究

装配序列生成是计算机辅助装配工艺规划（ＣＡＡＰＰ，ＣｏｍｐｕｔｅｒＡｉｄｅｄＡｓｓｅｍｂｌｙＰｒｏｃｅｓｓＰｌａａｎｉｎｇ）的关键环节。本文首先给出了基于特征产品装配模型，然后提出基于割集理论的装配序列自动生成算法。该算法根据评价准则采用ＡＯ搜索算法寻找最优的装配序列，既节省了装配成本和时间，又减少了算法的时间和空间复杂性。     

Disassembly method based on connection interface and mobility operator concepts

The impact of the disassembly process on the design of a product is a recognized fact, influencing recycling, maintenance, repair, and component/material re-using—essential aspects for a sustainable development. For simplifying and improving their work, as well as for designing proper and efficient disassembly plans, it is important for engineers to benefit from a disassembly method, for automatically generating dismounting sequences, incorporated in a software solution for providing rapid disassembly information that can be further used for real-time immersive simulations. The disassembly method proposed in this paper is based on two innovative elements: the connection interface concept and the mobility operator that integrates information on geometrical constraints, contact surface relative position and common area, neighboring components, and relative mobilities of the assembly components. All these data are corroborated with knowledge-based criteria and are used to generate a set of connection interfaces for a product to define mechanical joints, automating the identification of fasteners in the assembly and determining the components’ mobility within assembly. As a consequence, it is possible to calculate and realistically simulate components’ disassembly paths. In the proposed method, valid disassembly trajectories of a component relative to its surrounding ones are modeled based on the mobility operator, the swept volume approach is used to evaluate collisions between components, and finally, the disassembly sequences are determined through an improved layer peeling technique.     

Computer aided geometric feasible assembly sequence planning and optimizing

Assembly sequence planning (ASP) is the foundation of the assembly process planning and design for assembly (DFA). In ASP, geometric feasibility is the prerequisite in the valid assembly sequences searching. The assembly precedence relations’ (APRs) deriving and fulfilling are the essential tasks in the geometric feasible assembly sequence planning. In this paper, a systematical approach called geometric constraint analysis (GCA) is proposed and the corresponding software system is developed and integrated with CAD system. Using this system, only with a few mouse clicks on CAD draft, assembly precedence relations (APRs) can be derived correctly and completely. Then, all the geometric feasible assembly sequences can be inferred out automatically. Moreover, an optimal algorithm is designed and realized in the GCA method, by which, the most optimal assembly sequence in terms of the operation convenience can be found out from the immense geometric feasible sequences. An erratum to this article can be found at     

Flexible job shop scheduling with tabu search algorithms

This paper presents a tabu search algorithm that solves the flexible job shop scheduling problem to minimize the makespan time. As a context for solving sequencing and scheduling problems, the flexible job shop model is highly complicated. Alternative operation sequences and sequence-dependent setups are two important factors that frequently appear in various manufacturing environments and in project scheduling. In this paper, we present a model for a flexible job shop scheduling problem while considering those factors simultaneously. The purpose of this paper is to minimize the makespan time and to find the best sequence of operations and the best choice of machine alternatives, simultaneously. The proposed tabu search algorithm is composed of two parts: a procedure that searches for the best sequence of job operations, and a procedure that finds the best choice of machine alternatives. Randomly generated test problems are used to evaluate the performance of the proposed algorithm. Results of the algorithm are compared with the optimal solution using a mathematical model solved by the traditional optimization technique (the branch and bound method). After modeling the scheduling problem, the model is verified and validated. Then the computational results are presented. Computational results indicate that the proposed algorithm can produce optimal solutions in a short computational time for small and medium sized problems. Moreover, it can be applied easily in real factory conditions and for large size problems. The proposed algorithm should thus be useful to both practitioners and researchers.     

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.     

基于集对分析的装配顺序模糊评价决策方法的研究

综述了几种装配顺序评价决策方法 ,提出了以装配成本低为目标 ,以产品的并行度、重定向次数及装配操作改变为评价因素 ,应用集对分析理论和模糊评价决策理论分析评价装配顺序的新方法。实现了利用丰富的评价信息 ,从多角度反映装配顺序评价结果有效性和可靠性的目的。并以齿轮泵的装配顺序为例 ,对可行装配顺序进行评价 ,确定了较为理想的装配顺序     

A Column-Generation Approach for the Assembly System Design Problem with Tool Changes

This assembly system design problem (ASDP) is to prescribe the minimum-cost assignment of machines, tooling, and tasks to stations, observing task precedence relationships and cycle time requirements. The ASDP with tool changes (ASDPTCs) also prescribes the optimal sequence of operations at each station, including tool changes, which are important, for example, in robotic assembly. A unique solution approach decomposes the model into a master problem, which is a minimum-cost network-flow problem that can be solved as a linear program, and subproblems, which are constrained, shortest-path problems that generate station configurations. Subproblems are solved on state-operation networks, which extend earlier formulations to incorporate tooling considerations. This paper presents a specialized algorithm to solve the subproblems. Computational tests benchmark the approach on several classes of problems, and the results are promising. In particular, tests demonstrate the importance of using engineering judgment to manage problem complexity by controlling the size of state-operation networks     

Assembly planning using a novel immune approach

Inspired by the vertebrate immune system, artificial immune system (AIS) has emerged as a new branch of computational intelligence. This paper explores the application of AIS in the problem of assembly planning and proposes a novel approach, called the immune optimization approach (IOA), to generate the optimal assembly plan. Based on the bionic principles of AIS, IOA introduces manifold immune operations including immune selection, clonal selection, inoculation and immune metabolism to derive the optimal assembly sequence. Maintenance of population diversity, attention to the local as well as the global search, and employment of heuristic knowledge to direct the search of optimized assembly sequences are the major concerns of IOA. The details of IOA are presented and the immune operations are discussed. Two practical products are taken as examples to illustrate the validity of IOA in assembly planning, and encouraging solutions in quality and efficiency are achieved. Comparisons with genetic algorithm demonstrate that IOA finds the optimal assembly solution or near-optimal ones more reliably and more efficiently, indicating that IOA has potential and advantages in dealing with assembly planning.     

车身装配尺寸链生成方法

误差分析中装配函数的构造在装配体尺寸质量评价中扮演重要的角色。尺寸链的形成过程反映了装配函数的核心内容。针对柔性零件的装配连接特征,首先建立了车身装配尺寸链信息模型,通过路径搜索算法,提出车身装配体尺寸链的实现和生成方法。所生成的尺寸链综合考虑了设计要求、装配工艺（顺序）、接头形式等因素,为设计方案的优化评价提供了误差分析手段。     

Design automation and optimization of assembly sequences for complex mechanical systems

Assembly sequence design for a mechanical system can have significant impact on manufacturing cost and product quality. Traditionally, such a design process is largely based on experience and best practices, often ineffective and non-optimal as the system becomes complex. This paper proposes a new, systematic method for automatic assembly sequence design and optimization. Key elements include assembly modeling, sequence planning, locating scheme optimization, dimensional quality evaluation, and optimization. First, a directed graph and an assembly matrix are employed to describe the assembly relation of a system. Then, the feasible assembly sequences are generated through layered subassembly detection of adjacency matrices, filtered by engineering constraints. To evaluate quickly the assembly quality and compare the influences of different locating point schemes, a linear 3D variation propagation analysis model with deterministic locating principle is introduced. The optimal locating scheme is then selected using a genetic algorithm with the least variation propagation. Finally, the assembly dimensional quality for different sequences is evaluated and the optimal assembly sequences are achieved through genetic algorithms. A case of automotive body side assembly is presented to illustrate the whole methodology.     

装配规划中基于割集的装配顺序生成方法

针对装配规划提出一种新的装配零件关系的描述方法，该方法应用改进的关联图－优先约束关联图，描述装配零件间的连接关系、优先关系及约束关系。在生成产品装配顺序时，充分地把装配优先关系与割集法副合到装配顺序搜索中，有效地生成产品所有满足装配条件的装配顺序，为装配规划提供参考的装配工艺路径。     

An integrated method for block assembly sequence planning in shipbuilding

Many efforts in the past have been made to find more efficient methods for assembly sequence planning in machining area. While few researches reported in other area such as block assembly in shipbuilding industry. In general, a ship hull is built with hundreds of different blocks, most of which are complicated in structure and different from each other in assembly planning. Additionally, there may be a large number of feasible assembly sequences for any block. A better sequence can help to reduce the cost and time of the manufacture. Therefore, it is necessary to seek out the optimal sequence from all feasible ones. Currently, the assembly sequences are determined manually by some process engineers. Consequently, it is becoming a time-consuming task and cannot make the assembly plan consistent to improve productivity. In this paper, a methodology-integrated case-based reasoning and constraints-based reasoning is proposed to improve the assembly planning for complicated products. Besides, genetic algorithm is designed to evaluate and select the optimal sequence automatically from the reference ones. The validity of the method is tested using real blocks, and the results show that it can facilitate the optimal assembly sequences generation.     

INTEGRATED APPROACH TO ASSEMBLY SEQUENCE PLANNING OF C0MPLEX PRODUCTS

Assembly sequence planning will be more difficult due to the increasing complexity ofproducts. An integrated approach to assembly sequence planning of complex products applying de-composition-planning-combination strategy is presented. First, an assembly is decomposed into a hier-archical structure using an assembly structure representation based on connectors. Then, an assemblyplanning system is used to generate the sequences that are locally optimal for each leaf partition in thestructure hierarchy. By combining the local sequences systematically in a bottom-up manner andchoosing suitable ones from the merged sequences, the assembly sequence of each parent structureincluding the whole assembly is generated. An integrated system has been completed. A complexproduct is given to illustrate the feasibility and the practicality of the approach.     

INTEGRATED APPROACH TO ASSEMBLY SEQUENCE PLANNING OF COMPLEX PRODUCTS

Assembly sequence planning will be more difficult due to the increasing complexity of products. An integrated approach to assembly sequence planning of complex products applying decomposition-planning-combination strategy is presented. First, an assembly is decomposed into a hierarchical structure using an assembly structure representation based on connectors. Then, an assembly planning system is used to generate the sequences that are locally optimal for each leaf partition in the structure hierarchy. By combining the local sequences systematically in a bottom-up manner and choosing suitable ones from the merged sequences, the assembly sequence of each parent structure including the whole assembly is generated. An integrated system has been completed. A complex product is given to illustrate the feasibility and the practicality of the approach.     

基于人因仿真分析的装配序列评价模型及应用

为减少装配作业疲劳,降低动作强度,提高装配质量和效率,提出了一种基于人因工程仿真分析的装配序列综合评价模型。以装配序列的人因性能优劣为目标,创建了包含定量与定性指标在内的综合评价指标体系;提出了装配序列人因工程仿真分析模型,通过虚拟仿真技术与人因分析方法获取人因性能的基础指标属性值。采用客观自适应熵权法和改进模糊层次分析法分别确定各定量指标和定性指标的权重,利用三角模糊数定量化定性评价值,基于Topsis框架得到适合人体作业的最优装配序列。最后结合Tecnomatix数字化仿真平台将该评价模型应用于某航天产品减速器可行装配序列的优选,验证了方法的有效性。     

A multi-plant assembly sequence planning model with integrated assembly sequence planning and plant assignment using GA

In a multi-plant collaborative manufacturing system, the manufacturing operations and assembly operations for producing a product can be distributed at different plants at various locations. The components are assembled with assembly operations performed in a multi-plant assembly sequence. In this research, a multi-plant assembly sequence planning model is presented by integrating (1) assembly sequence planning, and (2) plant assignment. In assembly sequence planning, the components and assembly operations are sequenced according to the assembly constraints and assembly cost objectives. In plant assignment, the components and assembly operations are assigned to the suitable plants to achieve multi-plant cost objectives. The feasible assembly sequences are generated using the developed graph-based models of assembly precedence graphs and matrices. A genetic algorithm (GA) method is presented to evaluate the multi-plant assembly sequences with an objective of minimizing the total of assembly operational costs and multi-plant costs. The main contribution lies in the new model for multi-plant assembly sequence planning and the new GA encoding scheme for simultaneous assembly sequence planning and plant assignment. Example products are tested and discussed. The test results show that the presented method is feasible and efficient for solving the multi-plant assembly sequence planning problem.     

Generation of assembly models from kinematic constraints

In this paper, we propose a new joint-based assembly modeling method. In joint-based assembly modeling, the assembly constraints are specified on the components, but not on the geometric elements of the components. The proposed method generates assembly models from kinematic joint constraints by applying three procedures (1) to extract all feasible JMFs (Joint Mating Feature) for each mating component using information on joint constraints, (2) to derive mating alternatives for each pair of mating components after reducing the number of JMFs using the pruning criteria, and (3) to generate an assembly model by choosing the intended one from the mating alternatives for each pair of mating components and solving the JMF constraints. Since the joint constraints are expressed in terms of the relations between components rather than relations between geometric elements, the proposed method is more intuitive and natural for assembly modeling and supports modeling activities effectively by minimizing user interactions. By using joint mating constraints for assembly modeling, moreover, the kinematic behaviors of assemblies determined in the conceptual design stage can be directly applied and consistently maintained up to the detailed design stage. In the proposed method, it is also not necessary to re-input the mating constraints even when the component topology is changed.