Jean-Michel Henrioud

Integrated design of product families and assembly systems

This paper describes a methodology for the integrated design of product families and assembly processes. A product family is considered as a set of similar products whose main functions are identical. The primary goal is to obtain a unified and efficient assembly process for the whole product family. The product variations (e.g. dimensions, geometry, optional parts) and the assembly plans introduce the need for flexibility in the assembly process. Since flexibility implies more capital investments and productivity reduction, the minimization of the required flexibility is proposed as design criterion.

Assembly sequences, assembly constraints, precedence graphs

In this paper, the authors present a critical discussion on relations between assembly constraints, assembly sequences and precedence graphs and a method to generate precedence graphs from any given set of assembly sequences. It is demonstrated that it is generally impossible to encompass assembly constraints for any product into a single precedence graph but that it is possible to encompass them in a precedence hypergraph as long as no some soft constraints have not been used to produce the assembly sequences. When soft constraints like clusters of components or early realisations for some tasks are used, several precedence graphs are required and the proposed method does not apply.

Systematic generation of assembly precedence graphs

In this paper, the authors present a complete method allowing a systematic generation of assembly precedence graphs for mechanical products. The generated precedence graphs can be used as the input data of different assembly line design methods such as line balancing. This method involves two stages: the first stage generates all feasible operations from which the second stage determines all the precedence graphs. The first stage is already operational, thus our attention is paid to the description of the principle of the second stage and its mathematical support. The basic idea of this stage is to decompose the set of all feasible operations into several subsets which determine all the precedence graphs. The mathematical support of this idea is a fundamental theorem whose proof is given. Some notions are introduced in this paper, like the assembly graph and base graph. The algorithm of this stage is proposed.<<ETX>>

Systematic method for the design of flexible assembly systems

A method for the design of flexible assembly systems is presented. The approach involves two stages: the systematic determination of all the valid assembly plans and then, for each one, the determination of all the corresponding assembly systems. Each valid assembly plan is described by an assembly graph. All the valid partitions of this graph are provided. Each partition defines the structure of an admissible assembly system and each subgraph in each partition defines a workstation for the corresponding assembly system. A recursive algorithm is presented. It produces the admissible workstations. The method avoids the difficulties inherent in precedence graphs.<<ETX>>

An assembly-oriented product family representation for integrated design

This paper presents a product family representation model which was developed during a research project called CISAL, the purpose of which was to propose an integrated approach for the design of product families and their assembly system. This model is able to deal with partial information from the design of the product family, a situation that often occurs at early stages of the concurrent design of products and production means. The proposed model is assembly-oriented, because the project covered design for assembly, assembly planning, and line layout issues. In fact, it was developed on the basis of the design methodology itself. An originality of the design approach-which impacted the proposed model-is to decompose the product into so-called functional entities defined by the designer. The product family is then seen as an assembly of functional entities that can be analyzed, designed, and further assembled separately. Component variants are aggregated into generic components, and links between components become generic. The paper presents the essential concepts related to this product family representation, before showing their application to an illustrative industrial case study: a family of signaling relays.

Generation of precedence hypergraphs for assembly system design

Abstract In this paper, the authors propose an original method for the determination of precedence graphs for Assembly Line Design. This method is based on the transformation of a set of assembly sequences into an hypergraph including “and” and “or ” precedence relations between assembly tasks. The resulting hypergraph may be straightforwardly transformed into a set of ordinary precedence graphs. It is also possible to develop Assembly Line Balancing (or Assembly Line Design) algorithms directly from the proposed hypergraph. Copyright

Adaptive line balancing for flexible assembly systems

Random equipment incident is a major problem when scheduling flexible assembly systems (FASs). In this paper, the authors suggest a reactive scheduling approach through the parameter associated to the line balancing, the objective is to adapt the line balancing to the equipment state. The consistency technique is used to solve the balancing problem and an heuristic approach is provided for online scheduling. Finally, the results of a computer simulation, compared with another heuristic approach, are reported.<<ETX>>

Linguistic model and a control problem for assembly workstation

This paper proposes a control problem statement in the framework of supervisory control technique for the assembly workstations. A desired behaviour of an assembly workstation is analysed. The behaviour of such a workstation is cyclic and some linguistic properties are established. An algorithm for the computation of the supremo controllable language of the closed system desired language is proposed.

Algorithm for Reactive Scheduling in Flexible Assembly Systems

Abstract A flexible assembly system must face random incidents of the equipment. The scheduling system must decide if it is possible to continue the assembly process, due to a new tasks to-workstations assignment In this paper, the authors propose two algorithms for reactive task assignment. The algorithms are based on a specific assembly process model A searching technique is used for finding all the possible assignments.

Tasks-to-Workstations Assignment in Assembly Systems Using a Stochastic Algorithm

Abstract In this paper, the authors propose a stochastic algorithm for tasks to workstation assignment in assembly systems, that minimizes the lines cycle time. This kind of optimization problem, as like the assembly line balancing, leads to a graph partitioning problem meeting precedence constraints. The algorithm uses a stochastic search technique, which considers, as possible solutions, only partitions of the task set. It converges with probability 1 to a global minimum.