3,785 research outputs found
An Agent-Based Approach to Self-Organized Production
The chapter describes the modeling of a material handling system with the
production of individual units in a scheduled order. The units represent the
agents in the model and are transported in the system which is abstracted as a
directed graph. Since the hindrances of units on their path to the destination
can lead to inefficiencies in the production, the blockages of units are to be
reduced. Therefore, the units operate in the system by means of local
interactions in the conveying elements and indirect interactions based on a
measure of possible hindrances. If most of the units behave cooperatively
("socially"), the blockings in the system are reduced.
A simulation based on the model shows the collective behavior of the units in
the system. The transport processes in the simulation can be compared with the
processes in a real plant, which gives conclusions about the consequencies for
the production based on the superordinate planning.Comment: For related work see http://www.soms.ethz.c
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An Optimization Based Design Framework for Multi-Functional 3D Printing
This work investigates design analysis and optimization methods for the integration of
active internal systems into a component for manufacture using multi-material 3D printing
processes. This enables efficient design of optimal multifunctional components that exploit the
design freedoms of additive manufacturing (AM). The main contributions of this paper are in two
areas: 1) the automated placement and routing of electrical systems within the component volume
and, 2) the accommodation of the effect of this system integration on the structural response of
the part through structural topology optimization (TO). A novel voxel modeling approach was
used to facilitate design flexibility and to allow direct mapping to the 3D printer jetting nozzles.Mechanical Engineerin
High-Level Object Oriented Genetic Programming in Logistic Warehouse Optimization
DisertaÄŤnĂ práce je zaměřena na optimalizaci prĹŻbÄ›hu pracovnĂch operacĂ v logistickĂ˝ch skladech a distribuÄŤnĂch centrech. HlavnĂm cĂlem je optimalizovat procesy plánovánĂ, rozvrhovánĂ a odbavovánĂ. JelikoĹľ jde o problĂ©m patĹ™ĂcĂ do tĹ™Ădy sloĹľitosti NP-teĹľkĂ˝, je vĂ˝poÄŤetnÄ› velmi nároÄŤnĂ© nalĂ©zt optimálnĂ Ĺ™ešenĂ. MotivacĂ pro Ĺ™ešenĂ tĂ©to práce je vyplnÄ›nĂ pomyslnĂ© mezery mezi metodami zkoumanĂ˝mi na vÄ›deckĂ© a akademickĂ© pĹŻdÄ› a metodami pouĹľĂvanĂ˝mi v produkÄŤnĂch komerÄŤnĂch prostĹ™edĂch. Jádro optimalizaÄŤnĂho algoritmu je zaloĹľeno na základÄ› genetickĂ©ho programovánĂ Ĺ™ĂzenĂ©ho bezkontextovou gramatikou. HlavnĂm pĹ™Ănosem tĂ©to práce je a) navrhnout novĂ˝ optimalizaÄŤnĂ algoritmus, kterĂ˝ respektuje následujĂcĂ optimalizaÄŤnĂ podmĂnky: celkovĂ˝ ÄŤas zpracovánĂ, vyuĹľitĂ zdrojĹŻ, a zahlcenĂ skladovĂ˝ch uliÄŤek, kterĂ© mĹŻĹľe nastat bÄ›hem zpracovánĂ ĂşkolĹŻ, b) analyzovat historická data z provozu skladu a vyvinout sadu testovacĂch pĹ™ĂkladĹŻ, kterĂ© mohou slouĹľit jako referenÄŤnĂ vĂ˝sledky pro dalšà vĂ˝zkum, a dále c) pokusit se pĹ™edÄŤit stanovenĂ© referenÄŤnĂ vĂ˝sledky dosaĹľenĂ© kvalifikovanĂ˝m a trĂ©novanĂ˝m operaÄŤnĂm manaĹľerem jednoho z nejvÄ›tšĂch skladĹŻ ve stĹ™ednĂ EvropÄ›.This work is focused on the work-flow optimization in logistic warehouses and distribution centers. The main aim is to optimize process planning, scheduling, and dispatching. The problem is quite accented in recent years. The problem is of NP hard class of problems and where is very computationally demanding to find an optimal solution. The main motivation for solving this problem is to fill the gap between the new optimization methods developed by researchers in academic world and the methods used in business world. The core of the optimization algorithm is built on the genetic programming driven by the context-free grammar. The main contribution of the thesis is a) to propose a new optimization algorithm which respects the makespan, the utilization, and the congestions of aisles which may occur, b) to analyze historical operational data from warehouse and to develop the set of benchmarks which could serve as the reference baseline results for further research, and c) to try outperform the baseline results set by the skilled and trained operational manager of the one of the biggest warehouses in the middle Europe.
Nonpermutation flow line scheduling by ant colony optimization
A flow line is a conventional manufacturing system where all jobs must be processed on all machines with the same operation sequence. Line buffers allow nonpermutation flowshop scheduling and job sequences to be changed on different machines. A mixed-integer linear programming model for nonpermutation flowshop scheduling and the buffer requirement along with manufacturing implication is proposed. Ant colony optimization based heuristic is evaluated against Taillard's (1993) well-known flowshop benchmark instances, with 20 to 500 jobs to be processed on 5 to 20 machines (stages). Computation experiments show that the proposed algorithm is incumbent to the state-of-the-art ant colony optimization for flowshop with higher job to machine ratios, using the makespan as the optimization criterion
Simulation Optimization Studies of Routing and Process Flow Problems
Computer aided simulation is emerging as a powerful tool for numerical analysis and in conducting performance evaluations of complex systems that depend on a multitude of variables. The primary objective in such simulation studies is to gauge the performance of the system under a various constraints and operating conditions. The effects of changing the operating parameter space can thus be analyzed without having to implement costly changes. Simulations are also carried out for the baseline scenarios to verity and validate the basic underlying system model. In this thesis research, two practical problems were studied through numerical modeling, and optimized solutions obtained for both. Optimizing the pick-up and delivery routes using a commercial software tool was the first task. Optimization of a production assembly line using a discrete event simulation tool was the second project that was carried out. The primary objective for the first task was to explore various routing scenarios and determine delivery routes that would minimize the total network mileage, while maintaining the pick-up time slots requested by the clients. A related task was to evaluate the possible advantages of centralizing all routing activity from a single site, instead of the two-hub scenario currently in effect. A total of eight different scenarios were studied as part of this effort. The second task involved optimization of the throughput of a fuel injector plant by placing buffers within the assembly lines for increased productivity
Hybrid order picking : A simulation model of a joint manual and autonomous order picking system
Order picking is a key process in supply chains and a determinant of business success in many industries. Order picking is still performed manually by human operators in most companies; however, there are also increasingly more technologies available to automate order picking processes or to support human order pickers.
One concept that has not attracted much research attention so far is hybrid order picking where autonomous robots and human order pickers work together in warehouses within a shared workspace for a joint target. This study presents a simulation model that considers various system characteristics and parameters of hybrid order picking systems, such as picker blocking, to evaluate the performance of such systems. Our results show that hybrid order picking is generally capable of improving pure manual or automated order picking operations in terms of throughput and total costs. Based on the simulation results, promising future research potentials are discussed
A Review Of Design And Control Of Automated Guided Vehicle Systems
This paper presents a review on design and control of automated guided vehicle systems. We address most key related issues including guide-path design, estimating the number of
vehicles, vehicle scheduling, idle-vehicle positioning, battery management, vehicle routing, and conflict resolution. We discuss and classify important models and results from key publications in literature on automated guided vehicle systems, including often-neglected areas, such as idle-vehicle positioning and battery management. In addition, we propose a decision framework for design and implementation of automated guided vehicle systems, and suggest some fruitful research directions
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