Papers by Keyword: Assembly Sequence Planning

Abstract: There may be several feasible sequences of assembly operations for assembling a mechanical product. Requirement of fixtures for each assembly sequence are different and hence the assembly lead time. Assembly Sequence Planning (ASP) is the activity of finding sequence (s) of assembly operations which has improved productivity and reduced lead time. Generating such suitable assembly sequence (s) have always been a challenging research area because every product is special in terms of its design characteristics. Significant level of automation has been achieved in ASP but huge efforts are still required to enhance its performance through improvement of the existing algorithms and data structures. Identifying stable configurations between constituent parts of an assembly is one of such important concern to augment ASP. It helps reducing dependence on fixtures by driving the assembly process through more number of stable configuration stages making it economical in time and cost.The purpose of this piece of work is to formulate a method to obtain information rich stability predicate automatically through Computer Aided Design (CAD) interface for a mechanical product.The method is automatic and saves hours of time studying the assembly by a skilled and experienced assembly analyst.

Abstract: Assembly Sequence planning is one of the important stages during the product manufacturing process. For the purpose of effectively reducing the degree of complexity and improving the efficiency, the modeling method of assembly sequence planning based on connector structures is proposed. The concept of connector structure is presented, which is regarded as basic assembly units to cover features of assembly parts and package functional parts and connectors. The model of assembly sequence planning is built, which represents the precedence constraint relationship among connector structures. Finally, an example is studied and the model of assembly sequence planning based on connector structure is built to illustrate the effectiveness of the modeling method.

Abstract: Assembly sequence planning is one of the key technologies for virtual assembly. It mainly consists of three parts, i.e. assembly modeling, planning algorithm and evaluation of sequence planning. This paper presents an overview about the research status quo and methods of the above three parts, analyzes both the advantages and disadvantages of those research methods and their application scope and proposes the trends of their development.

Abstract: For the purpose of effectively reducing the degree of complexity and improving the efficiency, the method of assembly sequence planning based on connector structure and ant algorithm was proposed. The concept of connector structure was presented, which was regarded as basic assembly unit to cover features of assembly parts. Then, a model of assembly sequence planning was built, which represented the precedence constraint relationship among connector structures. Additionally, the combination of the connector structure concept and characteristics of ant colony algorithm was developed for generating optimal assembly sequences under the guidance of precedence relations in the model. Finally, an example was studied to illustrate the effectiveness of the strategy.

Abstract: Assembly Sequence Planning (ASP) is an essential question for aircraft assembly process design. Modern aircraft assembly contains plenty of complex shape components, which have so many assembly features to ensure, this leads to a large number of feasible assembly sequences using traditional sequence planning algorithms; and it is hard to evaluate the contribution to assembly quality for every sequence. A methodology called Key Characteristics Based ASP is proposed in this paper, which can significantly reduce unavailable sequences and ensure key features for quality in assembly process designing compared with previous methods. The methodology focuses on the final assembly quality and considers it as Assembly Key Characteristics (AKCs) in the beginning of assembly process design. With tools such as AKCs decomposition, Datum Flow Chain, precedence constraint matrix, the methodology describes the main process for ASP. To verify the technologys effectiveness, this paper presents an application of the algorithm in an aircraft component assembly by an 863 program.

Abstract: Assembly sequence planning (ASP) plays an important role in the production planning and should be optimized to minimize production time and cost when large numbers of parts and sub-assemblies are involved in the assembly process. Although the ASP problem has been tackled via a variety of optimization techniques, these techniques are often inefficient when applied to larger-scale problems. In this study, an approach using particle swarm optimization (PSO) is proposed to tackle one of the ASP problems which are optimizing the assembly sequence time. PSO uses a number of agents (particles) that constitute a swarm moving around in the search space looking for the best solution. Each bird, called particle, learns from its own best position and the globally best position. Experimental results show that PSO algorithm can produce good results in optimizing the assembly time, has a powerful global searching ability and fast rate of convergence.

Abstract: According to the characteristics and demands of assembly sequence planning (ASP) of complicated electromechanical products, the improved Ant-Colony algorithm is presented to solve the problem. In order to plan assembly sequence, Precedence Graph, which is created based on assembly model, is created to record precedence relations between components. Several mechanisms are designed to make the precedence relations correct and compendious. To examine the feasibility of the sequences for tool’s operation, a quick checking method is proposed based on Potential Interference Information, which is created by simulating the tool’s movement and checking the interference information in entire assembly. Then, the Ant Colony Algorithm is improved to generate optimal assembly sequences with the guidance of precedence relations. Two important influence factors have been taken into account in the method. (1) A Penalty-Evaporation mechanism is proposed for the algorithm to punish unfeasible solutions. (2) Via analyzing the effects of the parameters in the state transfer function, the better solution is obtained while change the fixed parameters to transforming with time. Finally, an example illustrates the effectiveness of the strategy.

Abstract: An assembly sequence planning (ASP) method that combined the advantages of ant colony system (ACS) and Max-Min ant system (MMAS) is proposed. To identify the best sequence easily, five optimization criterions are automatically quantified, including reorientation, parallelism, continuity, stability and auxiliary stroke, and then integrated into the multi-objective heuristic and fitness functions of ant colony optimization (ACO). To improve the search capability for the global-best sequence, several measures are presented from aspects of determining number of ant, max-min pheromone limits, performance appraisal for initial components allocation and the group method for same components. The ASP algorithm based on Max-Min ant colony system (MMACS) is proposed. An assembly planning system AutoAssem is developed based on Siemens NX platform, and the actual effectiveness of each optimization measure is testified through case study of a valve.

Abstract: The essentiality of assembly assessment and assembly optimization in design stage is analyzed, and the existent problems of conventional assembly design method are illuminated. ADMDMU (Assembly Design Method based Digital Mock-Up) is illuminated, and the process of ADMDMU established, and the ADMDMU architecture is given out. The key techniques of ADMDMU are analyzed, and include assembly design based KBE (Knowledge Based Engineering) and virtual assembly based physically attribute. According to physical attribute, physically based modeling, visual object movement control, force simulation method and assembly sequence planning method are emphatically illuminated. Assembly design system based DMU is established in foundation of ADMDMU.

Abstract: The aim of assembly sequence planning (ASP) is to achieve the best assembly sequence which assembly cost and time used is less. The geometrical feasibility of an assembly sequence is validated by the interference matrix of the product. The number of assembly tool changes and the number of assembly operation type changes are considered in the fitness function. To establish the mapping relation between ASP and particle swarm optimization (PSO) approach, some definitions of position, velocity and operator of particles are proposed. The difference of the proposed discrete PSO (DPSO) algorithm with the other algorithm is the emphasis on the geometrical feasibility of the assembly sequence. The geometrical feasibility is verified at the first and the every iteration. The performance and feasibility of the proposed algorithm is verified via a simplified engine assembly case.