Simulation-Based Control of Complex Material Handling Systems

2008-2009Material Handling (MH) consists in the movement and storage of parts, in a manufacturing or distribution process, from one location to another. Material Handling Systems (MHSs) are everywhere in production plants, assembly lines, product distribution, logistics, intermodal activities (railways, road transportation, container ships, etc..). They usually are distributed, sometimes itinerant and often mixed manned and automated. Although not adding value in the manufacturing process, MH usually influences great part of a company’s operation costs, especially, for example, in the food distribution chain. Due to the increasing demand for a high variety of products, flexibility and efficiency are two important keywords in MHSs. Optimizing MH activities means having shorter response times and an increased throughput of the plant. The importance of this optimization process is very high in today’s companies. Nowadays, the interest in this process is growing rapidly since several new technologies, like the Radio Frequency Identification (RFID) are available which finally allow to introduce an automation level to operating MHSs, almost without stopping operations and at a very low cost. In MHSs control iusses involve the problem of the optimal sequencing and scheduling of short-term activities. The so-called problem of "Dispatching” consists in defining a procedure to assign resources to missions. This is often made by using heuristic rules called Dispaching rules. For control purposes, a model of the system is necessary. Due to the complex and heterogeneous nature of MHSs, modeling approaches proposed in the literature are typically very specific and context-dependent. Moreover, the strong combinatorial nature of the control problem, and the presence of a great number of constraints to be considered, usually make the design of a control solution very tough. To devise a closed form analytical control action can require a great computational effort and could result not so convenient. Indeed, turbulence and variations in the input set of the system can suddenly make not more adequate a hardly designed control action. Thus, the choice of Dispatching rules as control actions, despite producing only local optimum solutions, is very usual for MHSs. Dispatching rules, indeed, result in a more reasonable and robust way to control MHSs since they are effective and computationally inexpensive. In the absence of a closed form control solution, Simulation is fundamental to evaluate the effects of a control action which cannot be analytically predicted. The outcome of the application of a rule or another can be easily tested via simulation and this is the reason why having a good model assumes a further major importance. In this thesis a unique arcchitecture for the modeling and the control of complex MHSs has been proposed.VIII n.s

Material handling systems for the fluidized-bed combustion boiler at Rivesville, West Virginia

The 300,000 lbs/hr steam capacity multicell fluidized-bed boiler (MFB) utilizes complex material handling systems. The material handling systems can be divided into the following areas: (1) coal preparation; transfer and delivery, (2) limestone handling system, (3) fly-ash removal and (4) bed material handling system. Each of the above systems are described in detail and some of the potential problem areas are discussed. A major potential problem that exists is the coal drying system. The coal dryer is designed to use 600 F preheated combustion air as drying medium and the dryer effluent is designed to enter a hot electrostatic precipitator (730 F) after passage through a cyclone. Other problem areas to be discussed include the steam generator coal and limestone feed system which may have operating difficulties with wet coal and/or coal fines

Stress analysis of the additional loading device of the bridge crane for weights up to 500 t

In this work, additional loading device of the bridge crane for loads up to 500t, used at the „Đerdap” Hydro power plant, is analysed. The main aim is to determine the stress state, especially the stress distribution along the cross sections at the position of the opening for weight attachment. The main reason for conducting this analysis was the fact that non-destructive examination (NDE) revealed some defects in the material. The stress values are determined using analytical and numerical methods. Both of them have shown that the safety factor value in the cross sections around the opening are acceptable, and that the material has sufficient remaining strength despite the defects observed using NDE

Issues in modelling and identification of Discrete Event Systems

2011 - 2012Discrete Event System (DES) are systems whose behavior is governed by discrete events occurring asynchronously over time and solely responsible for generating state transitions. DESs are particularly used in the field of the manufactured systems, handling systems and transportation systems: even if such system are being studying for long time, because of their complexity, they still present many issues that attract research interest. In particular this dissertation focuses about handling system modeling and DES identification. Obtaining a good model of a system (both time-driven and event-driven) allows to more easily execute operations as performance analysis, control, monitoring of system evolution. However, in some cases modeling of a system is not simple because of several complications due to the behavior of the system or of the context it belongs to. As example, sometimes, especially in the context of material handling and transportation, systems present both an event-driven and a time-driven behavior. In all that cases a very high accuracy is not requested it is usual neglect the latter and “looking” at the system as a DES (as example modeling a handling system it is possible to be interested in knowing if a vehicle is or not in a zone of the path while it is not important to know its exactly position). When the time-driven behavior plays a fundamental role in the obtaining the overall system performance, such dynamics cannot be neglected and they have to be explicitly modeled. This is the case, as example, of the automated warehouse systems, where the handling subsystem, as will be shown in the rest of this dissertation, presents time-driven dynamics that greatly influence the warehouse’s performance. Consequently a new way to model the system behavior has to be used. However, there are situation in which the difficult issue is not choosing the right formalism to model the system but it is the modeling itself. This is typical in many practical contexts, where it can occur that one has to work with unknown ready-made systems and no documentation about their behavior is available, or the model of a very complex system is needed. In these and other cases modeling becomes hard and another way to obtain the model of the system is needed: automated identification can be the solution. In the modeling environment, contribution of this thesis consists in presenting a new methodology to obtain a model oriented to the control and performance analysis of complex material handling systems that is highly modular, compact and made of parameterized modules. First a discrete event model is presented and then a new formalism that merges the concepts of Hybrid Petri Nets and Colored Petri Nets is introduced: the Colored Modified Hybrid Petri Nets (CMHPNs). Hence a new CMHPN model is proposed: it allows to model both the event nature and the continuous nature of the system. As more, to allow the monitoring of system evolutions, a freeware simulation tool for the CMHPNs is presented. Finally it is shown how the CMHPN model can be used to execute analysis and performance evaluation. Liveness analysis is performed by means of a hybrid automaton obtained from the net model. A deadlock prevention policy is synthesized working on an aggregated model. To prove the effectiveness of this new formalism an existing large automated warehouse system is presented as case study: its CMHPNs model is used to simulate the system behavior and to analyze the warehouse’s performance. In the identification environments, the guidelines of a new “active” approach to identify the model of a preexisting system is described. The proposed preliminary algorithm identifies a free labeled PN model on the basis of the observed output sequences and of the modifiable input consisting of the enabled controllable transitions set. The main idea is to use the knowledge of the set of enabled controllable transitions together with additional information on the conflicting transitions to accelerate the net identification with respect to the passive identification approaches. In particular, the system assumes that the maximum time that must elapse from the enabling of a transition until it fires is known and that it is possible to detect if the system is entered in a cyclic behavior. Using this additional information, it is possible to determine set of constraints to represent sequences that are not accepted by the system. Such constraints can be used to improve the net identification. [edited by author]XI n.s

Utilizing the Product Development Process to Bring an Idea from Concept to Production

The purpose of this thesis is to document and discuss the five-stage product development process starting with defining a problem and resulting in manufacturing a final product for sale as it was implemented in the Portable Fire Pit Center for Manufacturing Excellence Senior Capstone Project. This project was carried out over the course of the Fall 2019 and Spring 2020 semesters by a team consisting of three Undergraduate Mechanical Engineering majors and two Undergraduate Accountancy majors. The ultimate goal of the project was to carry out a full production run of the Portable Fire Pit outputting fifteen units meeting retail quality standards. At the onset of the project, a project management plan and product development schedule were created to sequence tasks and proportionally distribute labor and resources over the course of the project. The first step of the project plan was to begin the prototyping phase of the product development cycle. This involved creating an initial product design that included the features required to solve the initial problem and also implement principles of Design for Manufacturing and Assembly (DFMA). The second state of the development process was to create a final product design by carrying out market research, making iterative prototypes, and improving the original design. The third stage of development involved making preliminary plans for a full production run, estimating production cost and budget based off of this plan, and developing a mock business plan for our product. The fourth stage of the process involved setting up the process layout and testing a full production run, applying Lean manufacturing principles to increase optimization. The fifth and final stage consisted of ramping up to full production and doing an hour-long production run. The author of this thesis will carry out an analysis of the product development process and discuss the effectiveness of DFMA and Lean manufacturing principles as they were carried out in this project

Specification and Automatic Generation of Simulation Models with Applications in Semiconductor Manufacturing

The creation of large-scale simulation models is a difficult and time-consuming task. Yet simulation is one of the techniques most frequently used by practitioners in Operations Research and Industrial Engineering, as it is less limited by modeling assumptions than many analytical methods. The effective generation of simulation models is an important challenge. Due to the rapid increase in computing power, it is possible to simulate significantly larger systems than in the past. However, the verification and validation of these large-scale simulations is typically a very challenging task. This thesis introduces a simulation framework that can generate a large variety of manufacturing simulation models. These models have to be described with a simulation data specification. This specification is then used to generate a simulation model which is described as a Petri net. This approach reduces the effort of model verification. The proposed Petri net data structure has extensions for time and token priorities. Since it builds on existing theory for classical Petri nets, it is possible to make certain assertions about the behavior of the generated simulation model. The elements of the proposed framework and the simulation execution mechanism are described in detail. Measures of complexity for simulation models that are built with the framework are also developed. The applicability of the framework to real-world systems is demonstrated by means of a semiconductor manufacturing system simulation model.Ph.D.Committee Chair: Alexopoulos, Christos; Committee Co-Chair: McGinnis, Leon; Committee Member: Egerstedt, Magnus; Committee Member: Fujimoto, Richard; Committee Member: Goldsman, Davi

Optimization of job shop scheduling with material handling by automated guided vehicle

Job Shop Scheduling with Material Handling has attracted increasing attention in both industry and academia, especially with the inception of Industry 4.0 and smart manufacturing. A smart manufacturing system calls for efficient and effective production planning. On a typical modern shop floor, jobs of various types follow certain processing routes through machines or work centers, and automated guided vehicles (AGVs) are utilized to handle the jobs. In this research, the optimization of a shop floor with AGV is carried out, and we also consider the planning scenario under variable processing time of jobs. The goal is to minimize the shop floor production makespan or other specific criteria correlated with makespan, by scheduling the operations of job processing and routing the AGVs. This dissertation includes three research studies that will constitute my doctoral work. In the first study, we discuss a simplified case in which the scheduling problem is reformulated into a vehicle dispatching (assignment) problem. A few AGV dispatching strategies are proposed based on the deterministic optimization of network assignment problems. The AGV dispatching strategies take future transportation requests into consideration and optimally configure transportation resources such that material handling can be more efficient than those adopting classic AGV assignment rules in which only the current request is considered. The strategies are demonstrated and validated with a case study based on a shop floor in literature and compared to classic AGV assignment rules. The results show that AGV dispatching with adoption of the proposed strategy has better performance on some specific criterions like minimizing job waiting time. In the second study, an efficient heuristic algorithm for classic Job Shop Scheduling with Material Handling is proposed. Typically, the job shop scheduling problem and material handling problem are studied separately due to the complexity of both problems. However, considering these two types of decisions in the same model offers benefits since the decisions are related to each other. In this research, we aim to study the scheduling of job operations together with the AGV routing/scheduling, and a formulation as well as solution techniques are proposed. The proposed heuristic algorithm starts from an optimal job shop scheduling solution without limiting the size of AGV fleet, and iteratively reduces the number of available vehicles until the fleet size is equal to the original requirements. The computational experiments suggest that compared to existing solution techniques in literature, the proposed algorithm can achieve comparable solution quality on makespan with much higher computational efficiency. In the third study, we take the variability of processing time into consideration in optimizing job shop scheduling with material handling. Variability caused by random effects and deterioration is discussed, and a series of models are developed to accommodate random and deteriorating processing time respectively. With random processing time, the model is formulated as a Stochastic Programming Job Shop Scheduling with Material Handling model, and with deteriorating processing time the model can be nonlinear under specific deteriorating functions. Based on a widely adopted dataset in existing literature, the stochastic programming model were solved with Pyomo, and models with deterioration were linearized and solved with CPLEX. By considering variable processing time, the JSSMH models can better adapt to real production scenarios

Materyal Aktarma Sistemlerinin İyileştirilmesi ve Gıda Sektöründen Bir Örnek Olay Çalışması

Materyal aktarma sisteminin optimizasyonu ile do0ru malzemenin, do0ru zamanda, do0ru yerde, do0ru aralkta, do0ru ko#ullarda, uygun maliyetle ve do0ru miktarda ta#nmasn sa0lamak için kullanlan en do0ru yöntemin seçilmesi ifade edilmektedir. Literatürde skça kar#la#ld0 üzere, materyal aktarm ürünün maliyetini arttrrken, de0erine herhangi bir katkda bulunmamaktadr. Malzeme ta#mann maliyeti tam olarak ölçülememesine ra0men, pahal bir üretim faaliyeti oldu0u için i#letme maliyetleri içerisinde önemli bir paya sahip oldu0u genellikle kabul görmektedir. Tesis tipine ba0l olarak toplam maliyetlerin %10 ile %80'ini olu#turmaktadr. Malzeme aktarma sisteminin iyile#tirilmesi, gereksiz ta#malar ortadan kaldrarak çevrim zamann da azaltr, ve böylece çkt miktarnda da önemli bir art# sa0lar. Bu da üretim maliyetlerinde azalma demektir. Malzeme aktarma sisteminin seçimi ve fabrika ortamndaki kurulumu ise tesis yerle#imi ile ayr dü#ünülmeyecek bir planlama faaliyetidir. Dolays ile Bu çal#mada, çkt miktarndaki de0i#imler incelenmek amacyla bir benzetim modeli kurulmu# ve veriler benzetim programna aktarlm#tr. Benzetim sonuçlarna göre materyal aktarma için kullanlan arabalarn says ve bu ta#ma i#lemlerini etkileyebilece0i dü#ünülen di0er baz faktörler de0i#tirilerek benzetim modeli çal#trlm# ve sonuçlar incelenmi#tir. Sonuçlardan yola çklarak mevcut materyal aktarma sistemi ve ili#kili olarak tesis yerle#imi ile ilgili öneriler geli#tirilmi#tir."ncelenen örnek olayda, bir gda firmasnda yaplan analizlerde materyal aktarma sistemi ve ba0msz dü#ünülmesi mümkün olmayan i#yeri düzeni de göz önüne alnm# ve i#yerinde bir takm düzenlemeler yaplarak de0i#iklikler de0erlendirilmi#tir. Material handling uses the right method to provide the right amount of the right material at the right place, at the right time, in the right sequence, in the right position, in the right condition, and at the right cost. It is often stated that material handling only contributes to the cost of producing a product, rather than contributing to the value of a product. Although it is difficult to measure the cost of material handling exactly, it is generally agreed that it represents a significant portion of the cost of doing business. Depending on the type of facility, estimates ranging from 10 to 80% of the total cost have been made. To improve material handling systems will reduce unnecessary handlings and also cycle time. So the output rate can be increased by this manner. Material handling, if done properly, have a significant potential to add profits to a firm. By thinking this potential, a simulation working has been made, and data has been transferred to the simulation program. Simulation was run by altering variables transporter units used for material handling and affecting these handling operations in according to the outcomes from simulation program and has been evaluated results. The case study to be analysed is carried out in a food firm. In this firm material handling system and layout, which is impossible to think without material handling systems, has been taken into consideration and has been evaluated by implementing changes on layout by altering data

Contribution to the capacity determination of semi-mobile in-pit crushing and conveying systems

As ore grades decline, waste rock to ore ratios increase and mines become progressively deeper mining operations face challenges in more complex scenarios. Today´s predominant means of material transport in hard-rock surface mines are conventional mining trucks however despite rationalisation efforts material transportation cost increased significantly over the last decades and currently reach up to 60% of overall mining. Thus, considerations and efforts to reduce overall mining costs, promise highest success when focusing on the development of more economic material transport methods. Semi-mobile in-pit crusher and conveyor (SMIPCC) systems represent a viable, safer and less fossil fuel dependent alternative however its viability is still highly argued as inadequate methods for the long term projection of system capacity leads to high uncertainty and consequently higher risk. Therefore, the objective of this thesis is to develop a structured method for the determination of In-pit crusher and conveyor SMIPCC system that incorporates the random behaviour of system elements and their interaction. The method is based on a structured time usage model specific to SMIPCC system supported by a stochastic simulation. The developed method is used in a case study based on a hypothetical mine environment to analyse the system behaviour with regards to time usage model component, system capacity, and cost as a function of truck quantity and stockpile capacity. Furthermore, a comparison between a conventional truck & shovel system and SMIPCC system is provided. Results show that the capacity of a SMIPCC system reaches an optimum in terms of cost per tonne, which is 24% (22 cents per tonne) lower than a truck and shovel system. In addition, the developed method is found to be effective in providing a significantly higher level of information, which can be used in the mining industry to accurately project the economic viability of implementing a SMIPCC system

Development of the framework for a lean, energy efficient, and environmentally friendly port: umm qasr port as a Case Study

The research focus is to examine rigorously how the implementation of Lean within the Umm Qasr Port improves the operation processes and to explore the Lean impact on environment improvement and energy efficiency management. In this research, the ROPMEE model has been developed by the researcher to evaluate the service quality in the cargo delivery process in the Port of Umm Qasr as it covers all the functional and non-functional areas in the cargo delivery process compared to other quality dimensions. The findings confirm that the process quality dimension is the most influential factor in service quality in the Port of Umm Qasr. The reasons for the poor performance of current practices adopted by the port are the use of traditional ways of information flow and a decision-making process that requires more time and steps within the whole process. The lack of smooth process flow is a potential cause of bottlenecks within port operation that create serious problems not only for the customer but also for the port itself. In this research, a visual representation is created of how the current value stream map for different port processes has been established on the identification and elimination of non- value-added activity or “waste” involved in delivering services in Umm Qasr port for customers. A VSM tool was applied to visually map the cargo handling flow, ship entrance, ship maneuvering and cargo clearance to display the current and future states of processes in a way that highlights opportunities for improvement. Based on the defined and classified waste according to the seven deadly wastes of Lean, this research suggests a future value stream map for port processes. The impact of the identified wastes has been quantified in terms of cost, carbon dioxide emissions working time efficiency, and energy consumption cost. This research is the first attempt to develop a Lean port model for improving port processes, as there have been no previous studies aimed at providing a holistic framework for improving port performance, which can be used by other ports. Implementing the Lean approach requires a gradual shift in work culture by involving all port employees and customers in the continuous improvement process and changing the service delivery from a push to pull system