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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...
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Citations
... Джін та ін. запропонував орієнтований граф зв'язку для представлення процесу складання з інформацією про пріоритет вузла [16]. Хомем де Мелло і Сандерсон використовували метод «вирізки» для створення всіх вузлів складальної одиниці за допомогою графа зв'язку [17]. ...
Modern industrial production requires the improvement of assembly processes, and thus increase the level of automated intelligent sequence planning. Therefore, researches in the field of automation of the sequence of assembly of products in industries are relevant at this time. In today's world there is a need to develop complex, accurate products. Problems are created in industries due to the reduction of the life cycle of products. There is a need to study the problem of assembly planning to achieve the goal of practical implementation and standardization of assembly plans. Creating graphs of the addition process is one of the problems. The assembly planning system can reduce human intervention in the process and reduce computational effort. The finished assembly contains many components that can be assembled using many sequences. A review of the methods from the literature showed that although these methods increase the automation level, they still cannot be applied to actual production because they do not take into account the experience and knowledge that can play a major role in planning and are of great value. Assembly planning, relationship charts, priority charts. Improving the assembly planning system to create a communication schedule and an assembly priority schedule was proposed. The advanced system will be used to generate possible assembly sequences with subassembly identification. A system has been developed to create alternative possible assembly sequences that can be used by component part / product designers in the early stages. A system capable of generating assembly sequences for simultaneous assembly of multiple parts has been proposed. Conclusions and work results can be applied used and improved for more productive product development by designers in the early stages and faster assembly of products in enterprises. The paper did not consider practical limitations (gravity) and irreversible assembly operations, such as permanent fastening, welding etc. Кey words: assembly, blocking graph, relation graph, sequence
... Kara et al. [14] constructed the product assembly liaison diagram and assembly liaison diagram was combined with assembly precedence rules through the "ask-answer" method which was used to generate subassemblies and the disassembly sequences of the product. Jin et al. [15] defined the assembly precedence according to geometric and assembly process constraints, and proposed a multi-level assembly model represented by an improved directed liaison graph containing part mating or locating information. The search space of subassembly identification can be decreased to some extent by applying assembly precedence relations among parts. ...
The generation of sequence planning becomes a difficult task as the number of part increases. As a consequence, dividing the complex product into multiple subassemblies which contain relatively few parts will decrease sequence planning difficulty. In the process of product assembly, semantic knowledge is an important basis for subassembly identification. Therefore, a semantic knowledge-driven subassembly identification framework is proposed. Generating information and knowledge during product design stage can be effectively utilized to become a variety of input constraints in the process of subassembly identification, including non-geometric structure constraints and assembly process constraints. Firstly, an assembly semantic model framework is constructed by mapping among spatial objects, assembly process and assembly relations, which are defined with Web Ontology Language (OWL) assertions. Next, the datum parts can be determined according to assembly directed graph. The influence of non-geometric structure attributes and assembly process factors on the assemblability was quantitatively expressed in semantics, and the characterization values and comprehensive weight value were deduced through Semantics Web Rule Language (SWRL) rules to construct weighted assembly directed graph. Based on this, simplifying weighted assembly directed graph through node merging and assembling is utilized to identify subassembly. Finally, the effectiveness of the framework is verified by transmission subassembly identification. The main contribution is presenting an ontology-based approach for sub-assembly identification, which can provide a feasible solution for the issue that mathematics-based subassembly identification approaches have great difficulty in explicitly representing assembly experience and knowledge.
... Given the combinatorial nature of the ASG problem, identifying connections and identifying assembly or disassembly sequences becomes significantly more difficult and time consuming as the number of assembly parts increases. An approach using sub-assemblies to help determine assembly sequences has been developed by [34] and further developed by [19]. The authors specify a number of conditions in order to automatically identify parallel and serial subassemblies. ...
The recognized potential of cobots for industrial applications has been motivating a growing body of literature. As further research uncovers new potential applications, cobots are permeating into more more complex industrial applications. The inherent safety of cobots enables them to work at multiple levels of autonomy in close proximity with human operators. While this opens a range of new possibilities for human-robot collaboration, it also requires a different approach to assembly sequence generation. Most assembly sequence generation methods lack the flexibility to consider assembly tasks concurrently performed by operator and cobot. By splitting the products into sub-assemblies, the focus of both robot and human can be divided over multiple sub-assemblies assembled simultaneously or centered into a single sub-assembly for mutual assistance. In this paper, an algorithm for the identification of assembly task precedence is presented. Unlike most previous methods, by identifying sub-assemblies, their assembly precedence and that of their comprising parts, parallel task execution is not hindered by rigid linear assembly sequences. The output of the proposed algorithm allows for the creation of collaborative assembly sequences embedding resource capability, collaborative workplace design, and safety considerations. The proposed algorithm uses liaison and collision matrices as input as well as base part and sub-assembly content.
... Assembly precedence is then represented as arrowed lines between parts. Jin et al. [10] defined assembly precedence according to geometric and assembly process constraints. One of the merits advantages of this method is that the search space of SI will be reduced. ...
For complex products, the generation of an assembly or disassembly plan becomes a difficult task as the assembly parts’ numbers increase. To bypass this problem, the use of a subassembly concept represents an original technique. It aims to organize the multipart assembly product into some subassembly encapsulation. Each subassembly contains, relatively, a small number of parts. As a result, the assembly or disassembly plan problem becomes between the identified subassemblies and, in that case, can be generated easily. Despite the attractiveness of the subassembly concept, the identification of subassemblies from the CAD model product remains a relevant research subject to be improved. In fact, the resolution of the precedence relation problem from the CAD model data constitutes the biggest difficulty of this technique. In this work, a novel disassembly plan approach based on a subassembly concept is presented. The proposed approach starts with the investigation of the CAD assembly data to extract a contact matrix. Then, the extracted matrix is enriched by assembling conditions in order to search the set of base parts initiating subassemblies. Once the subassemblies were recognized, a new subassembly interference matrix is regenerated. The disassembly plan is carried out, between the known subassemblies, using a simplification method of subassemblies interference matrix. An example of the CAD assembly product is treated during this paper to clarify the different steps of the proposed approach. The simulated results of both subassembly identification and disassembly plan were compared to examples given by the literature in order to validate the developed approach.
... The assembly precedence is represented as arrowed lines between parts. Jin et al. [9] defined the assembly precedence according to geometric and assembly process constraints. Thanks to this method, the search space of SI will be reduced. ...
Seen the significant number of parts constituting a mechanism, assembly or disassembly sequence planning became a very hard problem. The subassembly identification concept can constitutes the most original way to solve this problem particularly for complex product. This concept aims to break down the multipart assembly product into particular number of subassemblies, and each subassembly is constituted by a small number of parts. Consequently the generation of assembly or disassembly sequence planning between parts can be determined relatively easily because it becomes between the subassemblies constituting the product. Then, each subassembly is assembled or disassembled using the same approach. In literature subassemblies identification approach from CAD model is not very developed and still a relevant research subject to be improved. In this paper, a novel subassemblies identification approach is presented. This proposed approach starts with the exploration of the CAD assembly data to get an adjacency matrix. Then, the extracted matrix is enriched by adding the contact in all directions in order to determine and to classify the base parts initiator of each subassembly. The next step is to identify subassemblies using a new matrix called sum matrix obtained from contact all direction matrix and fit matrix. For better discussing and explaining the stages of the proposed approach an example of CAD assembly product is presented in all sections of this paper.
... The assembly precedence is represented as arrowed lines between parts. Jin et al. [9] defined the assembly precedence according to geometric and assembly process constraints. Thanks to this method, the search space of SI will be reduced. ...
Assembly or disassembly sequence planning is a very hard combinatory problem while the assembly parts numbers become important. To reduce this difficulty, especially for the case of complex products, the subassembly identification concept can constitute an original way. It aims to decompose the complex assembly product into some subassembly entities containing a small number of parts. Consequently, the generation of assembly or disassembly sequence planning of parts becomes between the subassemblies and, in that case, can be determined relatively easily. Despite the prettiness of the subassembly method, the identification of subassembly from a computer-aided design (CAD) model remains a relevant research subject to be improved. In this paper, a subassembly identification approach is presented. The proposed approach begins with the exploration of the CAD assembly data to carry out an adjacency matrix. Then, to identify the subassemblies, the extracted matrix is transformed through three steps. The first step consists of idealizing this matrix by removing all connection parts identified by the Feature-Manager, which permits reducing its size. Afterward, based on the reduced matrix, an all-direction matrix is constructed to identify the base part of a subassembly. The third step consists of enriching the all-direction matrix by mounting conditions to construct the set of subassemblies. An example of a CAD assembly mechanism is presented in all sections of this paper in order to explain and discuss the steps of the proposed approach.
... The method of directed graph representation and analysis using an adjacency matrix is presented by Lin (1991). The matrix approach is used in ASP models by Santochi and Dini (1992), Lai and Huang (2004), Jin et al. (2010) and Suszyń ski et al. (2013). ...
Purpose:
The main aim of this article is to develop the method of generating assembly sequences, which can be used in the shipbuilding industry. The method must take into account the assumptions specific for assembly processes of large-size steel ship hulls, among others, a large number of connections, multi-stage and parallel assembly, set priority relations between connections.
Design/methodology/approach:
The assembly sequence is presented as a directed acyclic graph, which vertices are mutually uniquely assigned to connections on a hull structure. The minimization of the number of unmet priority precedence of performing connections has been proposed as a criterion of optimization. The genetic algorithm has been proposed as a method to solve problems.
Findings:
The proposed method allows to model the acyclic assembly process of welded structures and find solutions minimizing the objective function even for very complex problems. Because of this, the method has a chance to be used in shipbuilding.
Research limitations/implications:
Mathematical formulation of priority assumptions is quite laborious. The possibility of partial automation of this process should be considered. Due to the complexity of the problem a relatively simplified objective function has been proposed. In assembling a hull additional criteria should be taken into account. It is the direction of further research.
Practical implications:
The method can be successfully used in shipbuilding and in planning the production of other steel welded structures, among others, tanks, components of bridges, offshore structures. Examples of calculations were performed on an actual structure of a hull fragment.
Originality/value:
A new way of coding the acyclic serial-parallel sequence was designed. The proposed method allows to analyse the sequence using the graph theory. Original, two-part crossover and mutation operators for assembling sequence were proposed.
... Assembly optimization in the production planning stage deals with determination of optimum assembly sequence and determination of optimum location of each resource; researches on the assembly sequence optimization are done by the previous researchers and are useful for construct the assembly model [12][13][14][15][16][17]. Tseng et al. [18] use Guided-GAs to deal with the assembly sequence problem. ...
Assembly process modeling mechanism, which contains all the process elements, is crucial for assembly process planning. This study proposes an assembly process modeling mechanism based on the product hierarchy, and the assembly-by-disassembly approach is used for constructing the assembly process model. Firstly, three stage for process models called disassembly process model (DPM), rough assembly process model (RAPM), and finish assembly process model (FAPM) are presented, and the process information, such as the motion information, process marks is given. Secondly, the operation semantics for assembly process model is proposed to describe the physical constraints between parts and components. Thirdly, the establishing procedure of assembly process model is given, which includes establishing process of disassembly task tree, design process of disassembly process node, mapping process from DPM to RAPM, and mapping process from RAPM to FAPM four subprocesses. At last, a prototype assembly process planning system, called AMTProcesser, is developed based on the proposed modeling mechanism.
... Both approaches makes use of precedence graph and connection graph. Jin et al. proposed a directed liaison graph to represent an assembly with assembly precedence information [18]. Homem de Mello and Sanderson used the 'cut-set' method to generate all of the subassemblies of an assembly using liaison graph [19]. ...
Assembly planning is an important activity which directly governs more than 50% of the cost of products. Literature reveals that considerable theoretical work has been focused on assembly sequence planning but very little work addresses practical implementation. The assembly planning problem needs a special consideration on account of the need for partial constraints such as subassembly detection. This paper reports the design and implementation of a software system which automatically determines a product assembly sequence, and subassemblies, which can be assembled in parallel, given only the geometric description of the assembly. The system is conceptually divided into two stages. The first stage takes CAD model of the product assembly as input, which generates a contact relationship and precedence relationship to aid in the generation of assembly sequences. In the second stage the relationships generated in first stage are augmented with fastener information to determine the subassemblies. The software system developed was successfully tested on practical assemblies. Comparison with literature shows that this algorithm is not only fast but unlike other algorithms, it also gives sequences in which multiple parts can be assembled at a time.
... A precedence graph represents the different possible sequences of tasks that have to be accomplished before other tasks [86,194]. Appropriate assembly modeling is a key factor in generating assembly sequences [96,199]. ...
This paper reviews the state-of-the-art methodologies for developing computer-aided design (CAD) model based systems for assembly simulation, planning and training. Methods for CAD model generation from digital data acquisition, motion capture, assembly modeling, human–computer interface, and data exchange between a CAD system and a VR/AR system are described. Also presented is an integrated methodology for designing, planning, evaluating and testing assembly systems. The paper further describes the implementation of these methods and provides application examples of CAD model based simulation for virtual assembly prototyping, planning and training. Finally, the technology gaps and future research and development needs are discussed.
