A Multi-Objective Optimization Approach for Multi-Head Beam-Type Placement Machines

This paper addresses a highly challenging scheduling problem in the field of printed circuit board (PCB) assembly systems using Surface Mounting Devices (SMD). After describing some challenging optimization sub-problems relating to the heads of multi-head surface mounting placement machines, we formulate an integrated multi-objective mathematical model considering of two main sub-problems simultaneously. The proposed model is a mixed integer nonlinear programming one which is very complex to be solved optimally. Therefore, it is first converted into a linearized model and then solved using an efficient multi-objective approach, i.e., the augmented epsilon constraint method. An illustrative example is also provided to show the usefulness and applicability of the proposed model and solution method.PCB assembly. Multi-head beam-type placement machine. Multi-objective mathematical programming. Augmented epsilon-constraint method

AI and OR in management of operations: history and trends

The last decade has seen a considerable growth in the use of Artificial Intelligence (AI) for operations management with the aim of finding solutions to problems that are increasing in complexity and scale. This paper begins by setting the context for the survey through a historical perspective of OR and AI. An extensive survey of applications of AI techniques for operations management, covering a total of over 1200 papers published from 1995 to 2004 is then presented. The survey utilizes Elsevier's ScienceDirect database as a source. Hence, the survey may not cover all the relevant journals but includes a sufficiently wide range of publications to make it representative of the research in the field. The papers are categorized into four areas of operations management: (a) design, (b) scheduling, (c) process planning and control and (d) quality, maintenance and fault diagnosis. Each of the four areas is categorized in terms of the AI techniques used: genetic algorithms, case-based reasoning, knowledge-based systems, fuzzy logic and hybrid techniques. The trends over the last decade are identified, discussed with respect to expected trends and directions for future work suggested

Mathematical Modelling and Methods for Load Balancing and Coordination of Multi-Robot Stations

The automotive industry is moving from mass production towards an individualized production, individualizing parts aims to improve product quality and to reduce costs and material waste. This thesis concerns aspects of load balancing and coordination of multi-robot stations in the automotive manufacturing industry, considering efficient algorithms required by an individualized production. The goal of the load balancing problem is to improve the equipment utilization. Several approaches for solving the load balancing problem are suggested along with details on mathematical tools and subroutines employed.Our contributions to the solution of the load balancing problem are fourfold. First, to circumvent robot coordination we construct disjoint robot programs, which require no coordination schemes, are flexible, admit competitive cycle times for several industrial instances, and may be preferred in an individualized production. Second, since solving the task assignment problem for generating the disjoint robot programs was found to be unreasonably time-consuming, we model it as a generalized unrelated parallel machine problem with set packing constraints and suggest a tailored Lagrangian-based branch-and-bound algorithm. Third, a continuous collision detection method needs to determine whether the sweeps of multiple moving robots are disjoint. We suggest using the maximum velocity of each robot along with distance computations at certain robot configurations to derive a function that provides lower bounds on the minimum distance between the sweeps. The lower bounding function is iteratively minimized and updated with new distance information; our method is substantially faster than previously developed methods. Fourth, to allow for load balancing of complex multi-robot stations we generalize the disjoint robot programs into sequences of such; for some instances this procedure provides a significant equipment utilization improvement in comparison with previous automated methods

Assembly Line

An assembly line is a manufacturing process in which parts are added to a product in a sequential manner using optimally planned logistics to create a finished product in the fastest possible way. It is a flow-oriented production system where the productive units performing the operations, referred to as stations, are aligned in a serial manner. The present edited book is a collection of 12 chapters written by experts and well-known professionals of the field. The volume is organized in three parts according to the last research works in assembly line subject. The first part of the book is devoted to the assembly line balancing problem. It includes chapters dealing with different problems of ALBP. In the second part of the book some optimization problems in assembly line structure are considered. In many situations there are several contradictory goals that have to be satisfied simultaneously. The third part of the book deals with testing problems in assembly line. This section gives an overview on new trends, techniques and methodologies for testing the quality of a product at the end of the assembling line

Mathematical Modelling for Load Balancing and Minimization of Coordination Losses in Multirobot Stations

The automotive industry is moving from mass production towards an individualized production, in order to improve product quality and reduce costs and material waste. This thesis concerns aspects of load balancing of industrial robots in the automotive manufacturing industry, considering efficient algorithms required by an individualized production. The goal of the load balancing problem is to improve the equipment utilization. Several approaches for solving the load balancing problem are presented along with details on mathematical tools and subroutines employed.Our contributions to the solution of the load balancing problem are manifold. First, to circumvent robot coordination we have constructed disjoint robot programs, which require no coordination schemes, are more flexible, admit competitive cycle times for some industrial instances, and may be preferred in an individualized production. Second, since solving the task assignment problem for generating the disjoint robot programs was found to be unreasonably time-consuming, we modelled it as a generalized unrelated parallel machine problem with set packing constraints and suggested a tighter model formulation, which was proven to be much more tractable for a branch--and--cut solver. Third, within continuous collision detection it needs to be determined whether the sweeps of multiple moving robots are disjoint. Our solution uses the maximum velocity of each robot along with distance computations at certain robot configurations to derive a function that provides lower bounds on the minimum distance between the sweeps. The lower bounding function is iteratively minimized and updated with new distance information; our method is substantially faster than previously developed methods

DESIGN OF CRUCIAL ELEMENTS FOR INDUSTRIAL PLANTS, OFFSHORE PLATFORMS AND UNDERWATER FACILITIES

The paper proposes some specific models to be used in design of crucial elements for Industrial Plants that previously were not easy to be addressed by simulation due their functional complexity. As examples of these kinds of elements are proposed autonomous systems for fire fighting and/or emergencies for on-shore and off shore plants as well as equipment for underwater operations. The paper proposes use of MS2G Simulation Paradigm (Modeling, interoperable Simulation and Serious Games) as solution in these specific cases to test concepts and capabilities

AN INTEGRATED FRAMEWORK FOR APPLYING LEAN MANUFACTURING AND OTHER STRATEGIES IN MASS CUSTOMIZATION ENVIRONMENTS

Manufacturing organizations are facing fragmented markets and increased demand of variety from consumers. As a result, many of these firms have adopted mass customization manufacturing strategies in an effort to offer their customers the freedom of choice while maintaining operational efficiency. Lean manufacturing strategies have also seen heavy use in manufacturing environments. This study investigates the possibilities of integrating lean manufacturing principles and practices into mass customization environments in order to improve system performance. The feasibility of other manufacturing strategies such as agility, Quick Response Manufacturing and the Theory of Constraints assisting in the application of lean manufacturing for mass customization is also explored with the goal of developing a theoretical framework for the application of these manufacturing systems in different types of mass customization environments. The result of these investigations is tested and verified using a real world case study

Génération des séquences de désassemblage et leur évaluation : Intégration dans un environnement de réalité virtuelle

Integration of disassembly operations during product design is an important issue today. It is estimated that at the earliest stages of product design, the cost of disassembly operations almost represents 30 % of its total cost. Nowadays, disassembly operation simulation of industrial products finds a strong interest in interactive simulations through immersive and real-time schemes. In this context, in the first place, this thesis presents a method for generating the feasible disassembly sequences for selective disassembly. The method is based on the lowest levels of a disassembly product graph. Instead of considering the geometric constraints for each pair of components, the proposed method considers the geometric contact and collision relationships among the components in order to generate the so-called Disassembly Geometry Contacting Graph (DGCG). The latter is then used for disassembly sequence generation thus allowing the number of possible sequences to be reduced by ignoring any components which are unrelated to the target. A simulation framework was developed integrated in a Virtual reality environment thus allowing generating the minimum number of possible disassembly sequences. Secondly, a method for disassembly operation evaluation by 3D geometric removability analysis in a Virtual environment is proposed. It is based on seven new criteria which are: visibility of a part, disassembly angles, number of tools' changes, path orientation changing, sub-assembly stability, neck score and bending score. All criteria are presented by dimensionless coefficients automatically calculated, thus allowing evaluating disassembly sequences complexity. For this purpose, a mixed virtual reality disassembly environment (VRDE) is developed based on Python programming language, utilizing VTK (Visualization Toolkit) and ODE (Open Dynamics Engine) libraries. The framework is based on STEP, WRL and STL exchange formats. The analysis results and findings demonstrate the feasibility of the proposed approach thus providing significant assistance for the evaluation of disassembly sequences during Product Development Process (PDP). Further consequences of the present work consist in ranking the criteria according to their importance. For this purpose, moderation coefficients may be allocated to each of them thus allowing a more comprehensive evaluating method.De nos jours, l'intégration des opérations de désassemblage lors de la conception des produits est un enjeu crucial. On estime que dans la phase initiale de la conception d'un produit, le coût des opérations de désassemblage représente environ 30% de son coût total. Ainsi, la simulation des opérations de désassemblage de produits industriels trouve un fort intérêt pour des simulations interactives grâce à des programmes d'immersion et en temps réel. Dans ce contexte, dans un premier temps, cette thèse présente une méthode de génération des séquences de désassemblage possibles pour le désassemblage sélectif. La méthode est basée sur les niveaux les plus bas du graphe de désassemblage des produits. Au lieu de considérer les contraintes géométriques pour chaque paire de composants, la méthode proposée tient compte des contacts (relations géométriques entre les composants) et des collisions afin de générer le Graphe Géométrique de Contacts et de Désassemblage (DGCG). Celui-ci est ensuite utilisé pour la génération des séquences de désassemblage permettant ainsi de réduite le nombre de séquences possibles en ignorant les composants non liés avec la cible. Une application de simulation a été développée, intégrée dans un environnement de réalité virtuelle (RV) permettant ainsi la génération du nombre minimum de séquences possibles de désassemblage.Dans un second temps, une méthode d'évaluation des opérations de désassemblage par analyse géométrique 3D de l'amovibilité dans un environnement RV est proposée. Elle est basée sur sept nouveaux critères qui sont: la visibilité d'une pièce, les angles de désassemblage, le nombre des changements d'outils, le changement d'orientation des trajectoires, la stabilité des sous-ensembles, les angles de rotation du cou et flexion du corps. Tous ces critères sont présentés par des coefficients sans dimension calculés automatiquement par l'application développée, permettant ainsi d'évaluer la complexité des séquences de désassemblage. A cet effet, un environnement mixte de réalité virtuelle pour le désassemblage (VRDE) est développé, basé sur le langage de programmation Python, en utilisant deux bibliothèques : VTK (Visualisation Toolkit) et ODE (Open Dynamics Engine), les formats d'échange étant fichiers: STEP, WRL et STL. L'analyse des résultats obtenus démontrent la fiabilité de l'approche proposée fournissant ainsi une aide non négligeable pour l'évaluation des séquences de désassemblage lors de processus de développement de produits (PDP). Les autres conséquences de ce travail consistent à classer les critères en fonction de leur importance. A cet effet, des coefficients de modération peuvent être attribués à chacun d'eux permettant ainsi une méthode d'évaluation plus complète