Special Session on Industry 4.0

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Optimization of Simultaneous Scheduling for Machines and Automated Guided Vehicles Using Fuzzy Genetic Algorithm

Flexible manufacturing system (FMS) has been introduced by the researchers as an integrated manufacturing environment. Automated guided vehicles (AGVs) introduced as the main tool of material handling systems in FMS. While the scheduling of AGVs and machines are highly related; simultaneous scheduling of machines and AGVs has been proposed in the literature. Genetic algorithm (GA) proposed as a robust tool for optimization of scheduling problems. Setting the proper crossover and mutation rates are of vital importance for the performance of the GA. Fuzzy logic controllers (FLCs) have been used in the literature to control key parameters of the GA which is addressed as fuzzy GA (FGA). A new application of FGA method in simultaneous scheduling of AGVs and machines is presented. The general GA is modified for the aforementioned application; more over an FLC is developed to control mutation and crossover rates of the GA. The objective of proposed FGA method is to minimize the makespan, production completion time of all jobs that they are produced simultaneously. An optimal sequence of operations is obtained by GA. There is a heuristic algorithm to assign the AGVs to the operations. As the main findings, the performance of GA in simultaneous scheduling of AGVs and machines is enhanced by using proposed method, furthermore a new mutation operator has been proposed. Several experiments have been done to the proposed test cases. The results showed that tournament selection scheme may outperform roulette wheel in this problem. Various combinations of population size and number of generations are compared to each other in terms of their objective function. In large scale problems FGA method may outperforms GA method, while in small and medium problems they have the same performance. The fluctuation of obtained makespan in FGA method is less than GA method which means that it is more probable to find a better solution by FGA rather than GA

Towards an integrated technology management across the rail supply chain extended to society: building the case study on high-speed trains

The present paper was prepared for the course “Project III”, with the supervision of Prof. António Moniz, reporting on the author speaking notes at the Winter School on Technology Assessment, 6-7 December 2010, as part of the Doctoral Programme on Technology Assessment at FCT-UNL.The railway industry is pushing for market uptake of research for better and competitive products and services as resulted from the workshop of the European Railway Advisory Council held this year 2010. What seems less considered by the industry concerns is however the new paradigm resulting from the financial crisis from 2008 and, as important, the increasing exposure to social movements (this last one the focus of my research). In support, the present paper proposes to develop a scientific based methodology driven from technology assessment (TA) that manages research results within society. In a first instance such exercise should be limited to a specific technology in railways as it can be the High Speed (HS) train and the technologies it embeds. The high-speed trains integrate the most advanced technologies in the sector and represent billions of Euros of public investment, greater than for conventional lines. The expected impacts are to integrate the technology effort of all parties extended to society from early stage of design to latter market entry. This increases the rail industry competitiveness, enhances innovative technologies, and improves predictability of future social conditions while decrease risks of market failure.António Brandão Moniz (FCT-UNL) e Rosário Macário (IST-UTL

Towards an integrated technology management across the rail supply chain extended to society: building the case study on high-speed trains

The present paper was prepared for the course “Project III”, with the supervision of Prof. António Moniz, reporting on the author speaking notes at the Winter School on Technology Assessment, 6-7 December 2010, as part of the Doctoral Programme on Technology Assessment at FCT-UNL.The railway industry is pushing for market uptake of research for better and competitive products and services as resulted from the workshop of the European Railway Advisory Council held this year 2010. What seems less considered by the industry concerns is however the new paradigm resulting from the financial crisis from 2008 and, as important, the increasing exposure to social movements (this last one the focus of my research). In support, the present paper proposes to develop a scientific based methodology driven from technology assessment (TA) that manages research results within society. In a first instance such exercise should be limited to a specific technology in railways as it can be the High Speed (HS) train and the technologies it embeds. The high-speed trains integrate the most advanced technologies in the sector and represent billions of Euros of public investment, greater than for conventional lines. The expected impacts are to integrate the technology effort of all parties extended to society from early stage of design to latter market entry. This increases the rail industry competitiveness, enhances innovative technologies, and improves predictability of future social conditions while decrease risks of market failure.António Brandão Moniz (FCT-UNL) e Rosário Macário (IST-UTL

Enhancing the performance of automated guided vehicles through reliability, operation and maintenance assessment

Automated guided vehicles (AGVs), a type of unmanned moving robots that move along fixed routes or are directed by laser navigation systems, are increasingly used in modern society to improve efficiency and lower the cost of production. A fleet of AGVs operate together to form a fully automatic transport system, which is known as an AGV system. To date, their added value in efficiency improvement and cost reduction has been sufficiently explored via conducting in-depth research on route optimisation, system layout configuration, and traffic control. However, their safe application has not received sufficient attention although the failure of AGVs may significantly impact the operation and efficiency of the entire system. This issue becomes more markable today particularly in the light of the fact that the size of AGV systems is becoming much larger and their operating environment is becoming more complex than ever before. This motivates the research into AGV reliability, availability and maintenance issues in this thesis, which aims to answer the following four fundamental questions: (1) How could AGVs fail? (2) How is the reliability of individual AGVs in the system assessed? (3) How does a failed AGV affect the operation of the other AGVs and the performance of the whole system? (4) How can an optimal maintenance strategy for AGV systems be achieved? In order to answer these questions, the method for identifying the critical subsystems and actions of AGVs is studied first in this thesis. Then based on the research results, mathematical models are developed in Python to simulate AGV systems and assess their performance in different scenarios. In the research of this thesis, Failure Mode, Effects and Criticality Analysis (FMECA) was adopted first to analyse the failure modes and effects of individual AGV subsystems. The interactions of these subsystems were studied via performing Fault Tree Analysis (FTA). Then, a mathematical model was developed to simulate the operation of a single AGV with the aid of Petri Nets (PNs). Since most existing AGV systems in modern industries and warehouses consist of multiple AGVs that operate synchronously to perform specific tasks, it is necessary to investigate the interactions between different AGVs in the same system. To facilitate the research of multi-AGV systems, the model of a three-AGV system with unidirectional paths was considered. In the model, an advanced concept PN, namely Coloured Petri Net (CPN), was creatively used to describe the movements of the AGVs. Attributing to the application of CPN, not only the movements of the AGVs but also the various operation and maintenance activities of the AGV systems (for example, item delivery, corrective maintenance, periodic maintenance, etc.) can be readily simulated. Such a unique technique provides us with an effective tool to investigate larger-scale AGV systems. To investigate the reliability, efficiency and maintenance of dynamic AGV systems which consist of multiple single-load and multi-load AGVs traveling along different bidirectional routes in different missions, an AGV system consisting of 9 stations was simulated using the CPN methods. Moreover, the automatic recycling of failed AGVs is studied as well in order to further reduce human participation in the operation of AGV systems. Finally, the simulation results were used to optimise the design, operation and maintenance of multi-AGV systems with the consideration of the throughputs and corresponding costs of them.The research reported in this thesis contributes to the design, reliability, operation, and maintenance of large-scale AGV systems in the modern and rapidly changing world.</div

Intelligent Simulation Modeling of a Flexible Manufacturing System with Automated Guided Vehicles

Although simulation is a very flexible and cost effective problem solving technique, it has been traditionally limited to building models which are merely descriptive of the system under study. Relatively new approaches combine improvement heuristics and artificial intelligence with simulation to provide prescriptive power in simulation modeling. This study demonstrates the synergy obtained by bringing together the "learning automata theory" and simulation analysis. Intelligent objects are embedded in the simulation model of a Flexible Manufacturing System (FMS), in which Automated Guided Vehicles (AGVs) serve as the material handling system between four unique workcenters. The objective of the study is to find satisfactory AGV routing patterns along available paths to minimize the mean time spent by different kinds of parts in the system. System parameters such as different part routing and processing time requirements, arrivals distribution, number of palettes, available paths between workcenters, number and speed of AGVs can be defined by the user. The network of learning automata acts as the decision maker driving the simulation, and the FMS model acts as the training environment for the automata network; providing realistic, yet cost-effective and risk-free feedback. Object oriented design and implementation of the simulation model with a process oriented world view, graphical animation and visually interactive simulation (using GUI objects such as windows, menus, dialog boxes; mouse sensitive dynamic automaton trace charts and dynamic graphical statistical monitoring) are other issues dealt with in the study