产品装配顺序的层次化推理方法研究

提出一种装配优先关系分类模型，将装配顺序规划过程中的各种装配优先关系分为几种优先关系，确定性工艺优先关系和模糊性工艺优先关系3类。并在此基础上，提出层次化装配顺序推理方法，分别从装配顺序的几何可行性、工艺可行性和工艺优良性3个层次，对装配顺序进行递进推理，最终得到性能优良的装配顺序。开发的产品装配分析软件原型系统－－PAAS可以对复杂产品的装配顺序规划进行有效的分析和优化。     

COMPUTER-AIDED BLOCK ASSEMBLY PROCESS PLANNING IN SHIPBUILDING BASED ON RULE-REASONING

Computer-aided block assembly process planning based on rule-reasoning are developed in order to improve the assembly efficiency and implement the automated block assembly process planning generation in shipbuilding. First, weighted directed liaison graph （WDLG） is proposed to represent the model of block assembly process according to the characteristics of assembly relation, and edge list （EL） is used to describe assembly sequences. Shapes and assembly attributes of block parts are analyzed to determine the assembly position and matched parts of parts used frequently. Then, a series of assembly rules are generalized, and assembly sequences for block are obtained by means of rule reasoning. Final, a prototype system of computer-aided block assembly process planning is built. The system has been tested on actual block, and the results were found to be quite efficiency. Meanwhile, the fundament for the automation of block assembly process generation and integration with other systems is established.     

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     

Imperialist competitive algorithm for assembly sequence planning

Automated generation of all feasible assembly sequences for a given product is highly desirable in manufacturing industry. Many research studies in the past decades described efforts to find more efficient algorithms for assembly sequence planning. Imperialist competitive algorithm for assembly sequence planning is presented in this paper. Population individuals called countries are in two types: colonies and imperialists that all together form some empires. Each assembly sequence is encoded into the country. The proposed algorithm is tested and compared with genetic algorithm and particle swarm optimization. Results show that imperialist competitive algorithm can improve the quality in solution searching and upgrade the opportunity to find optimal or near-optimal solution for assembly sequence planning.     

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.     

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.     

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.     

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.     

几何增强的装配工艺本体建模

包含产品几何与非几何信息的产品装配要求是装配工艺设计的主要依据,对装配工艺设计决策结果具有决定性的影响。在装配工艺模型中描述产品的几何相关信息能够更好地表达如装配顺序,装配路径等内容,同时可以更好地辅助装配工艺决策,提高决策的自动化水平。提出一种几何增强的装配工艺本体模型,利用语义本体技术,建立产品几何信息在装配工艺中的描述方法,数据结构与关系描述。并以该模型为基础,建立基于几何增强装配工艺本体的装配工艺决策框架。该框架分为两部分：一是采用几何增强的装配工艺本体模型描述产品几何信息和装配工艺信息的数据结构和相互关系;二是为了让几何信息与装配工艺信息之间存在的丰富的隐含关系显性化,对语义本体推理机制进行增强,提出推理单元的概念,使决策框架具有从产品几何信息中推理装配工艺相关信息的能力,有效地支持装配工艺决策。以针对某传动器产品装配顺序决策的过程,验证所提出的几何增强装配工艺本体模型与框架的有效性。     

基于质量特征产品装配顺序规划的逆向推理算法探究

在Petri网柔性装配系统装配顺序规划中引入装配质量要素,并以装配零件的装配自由度,装配作业后稳定性,装配零件配合精度对装配质量的影响作为基本因子,提出装配质量置信度概念,解决柔性装配系统装配规划中装配质量及其定量化问题。根据装配形成的产品在Petri网装配状态图中表示为一个最终库所的特点,应用改进B树模型,提出仅以变迁信息的产品装配顺序规划Petri网逆向推理算法,简化装配顺序规划推理过程,对于多个变迁均可生成最终成品的情况,亦给出装配顺序规划的解决方案,并以摩托车发动机的装配为例,证明该算法是可行的。     

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.     

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。     

基于推理的有向图拓扑排序装配顺序规划及优化研究

装配顺序规划是虚拟装配中的重要研究内容。在阐述有向图拓扑排序技术原理的基础上,研究了基于推理的将有向图拓扑排序技术应用到产品装配顺序规划中的方法,探讨了应用可装配性评价技术得出最优装配顺序的途径。依据这些理论和算法在MDT平台上开发了一个箱体类产品的装配顺序自动规划系统,并以一个齿轮减速器为例进行了验证。     

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.     

计算机辅助几何可行装配顺序推理及其优化分析

针对装配优先关系分析、几何可行装配顺序推理以及最优几何可行装配顺序选择3个层次的问题,提出了一种系统化的分析方法——几何约束分析方法。该方法从装配体中各个零件之间的约束方向分析出发,可以自动求解出正确和完备的装配优先关系在装配优先关系的约束下,可以计算出所有的几何可行装配顺序规划;并从操作空间大、装配方便角度出发,设计出几何可行装配顺序优选算法,可以从大量的几何可行装配顺序中求解出几何性能最佳的装配顺序规划。应用具体实例分析演示了几何约束分析方法在计算机中的实现过程,并证实了该方法的实用性和有效性。     

基于遗传算法的装配序列规划研究

分析了传统装配序列规划的不足，建立了考虑子装配体稳定性的目标函数，采用带记忆的遗传算法进行装配序列规划；在初始种群生成时，可以输入带专家知识的可行装配序列改善种群的组成成份；在各种群的生成过程中，始终保留所获得的当前最优可行装配序列，确保算法最终收敛到最优或近优解。最后以实例说明该方法的有效性。     

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 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).