In today’s competitive market, a company will not succeed unless they stand out in other ways than pure benefits with its products. This can be reached by in some way altering the process currently in place. One way, is by introducing process innovation. Advantages related to the adoption of process innovation has been found in literature, for example by increase competitiveness, increase productivity, and increase plant visibility. However, process innovation evokes uncertainty. Discrete Event Simulation (DES) models has in previous research been suggested as a tool to reduce uncertainty at manufacturing companies when they are undergoing changes. However, the study of change in process innovation setting has been largely ignored. By acknowledging this gap in current research, the aim of this study is to investigate whether the use of DES models are able to reduce uncertainties in process innovation. The study is guided by three research questions: 1. What are the characteristics of process innovation introduction in a production process context? 2. How is the production process at manufacturing companies affected by process innovation related uncertainties? 3. How can the usage of DES contribute to reduction of uncertainties during the introduction of process innovation at manufacturing companies? In order to answer these questions, a research methodology consisting of a literature review and a case study including the usage of DES were applied. In this thesis the case study is conducted at a manufacturing company, presented with the goal of making a modification in the production. This is done in an attempt to make it more environmental friendly while also establish a competitive edge over the rivals. To reach this, an implementation of a process innovation technology is under planning, but introducing something new creates numerous uncertainties. To be able to implement this process innovation, uncertainty reduction is crucial. By identify literature within the field, and compare with findings from interviews and workshops at the studied company, process innovation characteristics and how process innovation evokes uncertainties were identified. From the usage DES in this thesis, uncertainties were reduced, partly reduced and identified while some uncertainties remain unresolved. Moreover, the findings point to the creation of the simulation model working as a visualisation of the current production and the possible future, which generates a discussion platform for all stakeholders involved. / I den nuvarande konkurrenskraftiga marknaden har ett företag många utmaningar ifall de vill lyckas. Det räcker nämligen inte längre med att ha bra produkter utan de måste också förbättras på andra sätt. Ett sätt att uppnå detta på, är att genomföra förändringar i den nuvarande produktionen, en metod för detta är introducera en processinnovation på företaget. Under detta arbete har fördelarna relaterade till processinnovation upptäckts i befintlig litteratur, till exempel genom att ökad konkurrentskraftighet, produktivitet och synlighet för fabriken. Dessvärre framkallar implementeringen av en processinnovation osäkerheter. Diskret händelse simulering (DES) modeller har i tidigare forskning föreslagits som ett verktyg för at minska osäkerheter i tillverkningsföretag, medan de planerar att genomgår en förändring. Forskning om hur simulering hanterar fabriker som genomgår en processinnovation har i hög grad ignorerats. De här studien har för avsikt att undersöka just det området där nuvarande forskning brister, nämligen om ifall DES modeller kan minska osäkerheter i processinnovationer. Tre forskningsfrågor har tagits fram för att styra arbetet: 1. Vilka kännetecken har introduktionen av processinnovation i en produktionsprocess kontext? 2. Hur påverkas produktionsprocess hos tillverkande företag av de osäkerheter som processinnovation medför? 3. Hur kan DES användas för att bidra till minskandet av osäkerheter i tillverkande företag som introducerar processinnovation? För att besvara dessa frågor genomfördes an litteraturstudie och en fallstudie som innehöll simulering. Fallstudien som utfördes på ett tillverkningsföretag som är i planeringsstadiet för att införa en processinnovation. Innovationen har för avsikt att göra produktionen mer miljövänlig och samtidigt skapa en fördel över konkurrenterna. Nuvarande planering är fylld av osäkerheter eftersom tillägget av någonting nytt alltid gör det. Därför är reduceringen av osäkerheter avgörande för att en implementering ska kunna genomföras Genom att identifiera forskning inom området, och jämföra den med resultat från företagsrelaterade intervjuer och workshops, identifierade kännetecken på processinnovation och hur processinnovation skapar osäkerheter. Genom att använda DES i examensarbetet, minskades antalet osäkerheter, till fullo och delvis, och nya osäkerheter identifierades. Dessutom visar resultat på studien att simulering kan användas som ett visualiseringsverktyg för att skapa en diskussionsplattform angående framtida förändringar i produktionen.

De nombreux systèmes de transport peuvent être modélisées par des synchronisations ordinaires (pour tout k>=l, l'occurrence k de l'événement B se produit au moins t unités de temps après l'occurrence k-l de l'événement A). Ces systèmes sont linéaires dans l'algèbre (max,+). Pour certaines applications, il est primordial de modéliser la simultanéité entre événements. Comme la synchronisation ordinaire ne suffit pas à exprimer ce phénomène, nous introduisons la synchronisation partielle (l'événement B ne peut se produire que quand l'événement A se produit). Dans ce mémoire, des méthodes développées pour la modélisation et le contrôle de systèmes linéaires dans l'algèbre (max,+) sont étendues à des systèmes régis par des synchronisations ordinaires et partielles. Nous considérons uniquement des systèmes divisés en un système principal et un système secondaire et gouvernés par des synchronisations ordinaires entre événements dans le même système et des synchronisations partielles d'événements dans le système secondaire par des événements dans le système principal. Nous introduisons une commande optimale et une commande prédictive pour cette classe de systèmes par analogie avec les résultats disponibles pour les systèmes linéaires dans l'algèbre (max,+). En considérant un comportement donné pour le système principal, il est aussi possible de représenter le système secondaire par une fonction de transfert et de modifier sa dynamique pour suivre un modèle de référence. / Many transportation networks can be modeled by (max,+)-linear systems, i.e., discrete event systems ruled by standard synchronizations (conditions of the form: "for all k>=l, occurrence k of event B is at least t units of time after occurrence k-l of event A"). In some applications, it is also necessary to model simultaneity between events (e.g., for a road equipped with traffic lights, a vehicle can cross an intersection only when the associated traffic light is green). Such conditions cannot be expressed using standard synchronizations. Hence, we introduce the partial synchronization (condition of the form: "event B can only occur when event A occurs"). In this thesis, we consider a class of discrete event systems ruled by standard and partial synchronizations, called (max,+)-systems with partial synchronization. Such systems are split into a main system and a secondary system such that there exist only standard synchronizations between events in the same system and partial synchronizations of events in the secondary system by events in the main system. We adapt some modeling and control approaches developed for (max,+)-linear systems to (max,+)-systems with partial synchronization. Optimal feedforward control and model predictive control for (max,+)-linear systems are extended to (max,+)-systems with partial synchronization. Furthermore, transfer relation and model reference control are provided for the secondary system under a predefined behavior of the main system.

A master thesis within mechanical engineering performed by two student has been conducted at Scania in Oskarshamn. The purpose has been to investigate if Discrete Event Simulation using ExtendSim can be applied to increase Scanias assembly productivity. The projectiles was to investigate how the buffer systems could be managed by vary the amount of buffers and their transport speed. The assembly line takt times with regard of their availability was also investigated. The method of approach was to build a simulation model to gaining valid decision making information regarding these aspects. Process stop data was extracted and imported to ExtendSim where the reliability library was used to generate shutdowns. Comparing 24 sets over 100 runs to each other a median standard deviation of 0,91 % was achieved. Comparing the total amount of assembled cabs over a time period of five weeks with the real timedata a difference of 4,77 % was achieved. A difference of 1,85 % in total amount of shutdown time was also achieved for the same conditions. The biggest effect of varying buffer spaces was for system 6A. An increasement of up to 20 more assembled cabs over a time period of five weeks could then be achieved. By increasing all the buffertransports speeds by 40 % up to 20 more assembled cabs over a time period of ve weeks could be achieved. A push and pull system was also investigated where the push generated the best results. A 22 hour decreasement of total shutdown time and an increasement of 113 more assembled cabs over a time period of ve weeks could be achieved.

Newsvendor problems in Operations Research predict the optimal inventory levels necessary to meet uncertain demands. This thesis examines an extended version of a single period multi-product newsvendor problem known as the ice cream vendor problem. In the ice cream vendor problem, there are two products – ice cream and hot chocolate – which may be substituted for one another if the outside temperature is no too hot or not too cold. In particular, the ice cream vendor problem is a data-driven extension of the conventional newsvendor problem which does not require the assumption of a specific demand distribution, thus allowing the demand for ice cream and hot chocolate respectively to be temperature dependent. Using Discrete Event Simulation, we first simulate a real-world scenario of an ice cream vendor problem via a demand whose expected value is a function of temperature. A sample average approximation technique is subsequently used to transform the stochastic newsvendor program into a feature-driven linear program based on the exogenous factors of probability of rainfall and temperature. The resulting problem is a multi-product newsvendor linear program with L1-regularization. The solution to this problem yields the expected cost to the ice cream vendor as well as the optimal order quantities for ice cream and hot chocolate, respectively.

This thesis assesses the potential of using computer simulation to aid existing lean manufacturing training methods such as lecture and live simulation. An investigation of this possibility was carried out in conjunction with UMEP's Lean 101 class. In the study, two experimental computer simulation models demonstrating the push and pull production scenarios were constructed using ProModel software. Simulation models were equipped with a Visual Basic interface to aid trainees to manipulate the model via ActiveX. Constructed computer simulation was compared with live simulation to answer these research questions: 1. Was computer simulation able to teach additional lean concepts not covered in live simulations? 2. Was training time less for trainees going through a computer simulation than for those going through a live simulation? 3. Was a computer simulation quicker and easier to set up than a live simulation for trainers? 4. Did computer simulation achieve comparable educational objectives as live simulation? Objective measurements for first three questions were positive and conclusive. For the fourth one, a survey was conducted among trainees of a treatment group (computer simulation only) and a control group (live simulation only) to collect responses. Statistical analysis of the subjective responses indicated the computer simulation aided the trainees to learn and implement lean manufacturing, but was not as effective as live simulation. Holistically, these results did not warrant the complete changeover from live simulation to computer simulation. Yet, a combined implementation of computer simulation and live simulation was proposed to reap the benefits from the best of both approaches.

This thesis is focused on using discrete event simulation in a large plant in order to improve the control logic of the production department. Specifically it’s about the factory ŠKODA AUTO a.s. located in Mladá Boleslav and solved production node is the paint shop area. The chapters of this thesis are focused on used conveyor technology, basics of discrete event simulation, the subsequent development of a virtual model, design of simulation experiments and concept of a new solution. At the end of this work evaluation of proposed solution with comparison to the original solution is included.

Cette thèse porte sur le diagnostic des défauts dans des Systèmes à Evènements Discrets (SED) pour lesquels l’occurrence des événements est soumise à des contraintes temporelles. Les domaines d’application potentiels sont nombreux et variés allant de la production manufacturière aux systèmes de transport en passant par les réseaux de communication et les systèmes d’information. La complexité croissante de ces systèmes nécessite l’élaboration de méthodes de surveillance de plus en plus efficaces et performantes pour garantir leur sécurité, leur disponibilité ainsi que le maintien de leurs propriétés dans le temps. Les réseaux de Petri Stochastiques Temporisés Partiellement Observés (RdPSTPO) sont utilisés pour modéliser le système ainsi que les défauts qui peuvent l’affecter. L’étude concerne particulièrement les défauts qui se traduisent par la violation des contraintes temporelles. Une exploitation pertinente des informations temporelles, en vue du diagnostic, constitue la contribution majeure de la thèse. En effet, une meilleure utilisation de ces informations permet de discerner avec précision les différents comportements qui expliquent les mesures. De plus, la probabilité d’occurrence des défauts est calculée en fonction des dates des mesures collectées. Deux approches sont développées : la première est dédiée aux défauts ponctuels et la seconde aux dérives lentes dans les systèmes cycliques. / This PhD thesis deals with the fault diagnosis of Discrete Event Systems (DES) for which the occurrence of events is constrained by temporal specifications. The domain of application is large and varied ranging from manufacturing systems to transportation systems, communication networks and information systems. The increasing complexity of these systems requires the development of effective and efficient monitoring methods to ensure their security, availability and the maintenance of their properties over the time. For that purpose, Partially Observed Stochastic Timed Petri Nets (POSTPN) are used to model the system and the different faults that may affect it. The study is particularly concerned with faults that result after the violation of temporal constraints. Our main contribution in this thesis is the relevant exploitation of the timed information for the fault diagnosis. In fact, a better use of these temporal informations allow to discern with precision the different behaviors that are consistent with the measurements. In addition, the probability of faults occurrence is evaluated according to the dates of collected measurements. Two approaches are developed : the first one is used for single faults and the second one for slow drifts in cyclical systems.

This paper presents an efficient and accurate analytical model for the radio interface of the general packet radio service (GPRS) in a GSM network. The model is utilized for investigating how many packet data channels should be allocated for GPRS under a given amount of traffic in order to guarantee appropriate quality of service. The presented model constitutes a continuous-time Markov chain. The Markov model represents the sharing of radio channels by circuit switched GSM connections and packet switched GPRS sessions under a dynamic channel allocation scheme. In contrast to previous work, the Markov model explicitly represents the mobility of users by taking into account arrivals of new GSM and GPRS users as well as handovers from neighboring cells. Furthermore, we take into account TCP flow control for the GPRS data packets. To validate the simplifications necessary for making the Markov model amenable to numerical solution, we provide a comparison of the results of the Markov model with a detailed simulator on the network level.

Behovet av akut vård har ökat under de senaste åren och satt ökad press på ambulanssektorn i stort. Hur man kan förbättra och effektivisera olika delar av vårdkedjan är en fråga som beslutsfattare inom denna sektor ständigt behöver ha i åtanke för att kunna möta detta behov. Det finns visioner om en likvärdig vård för alla människor i vårt samhälle, som tyvärr kan vara svåra att nå i praktiken. Människor som bor i glesbefolkade områden behöver i regel vänta längre på en ambulans än personer som bor i urbana områden, och transporttiden för dessa ambulansutryckningar blir längre eftersom det ofta är långt till närmaste akutmottagning. För ambulanspersonalen kan det dessutom i vissa fall vara svårt att göra en korrekt bedömning om huruvida en mindre akut patient behöver transporteras till en akutmottagning eller inte. En tänkbar förändring i vårdkedjan kan vara att transportera mindre akuta patienter till en närliggande vårdcentral istället för en akutmottagning - en så kallad alternativ vårdväg. Detta hade både kunnat resultera i kortare transporttider på glesbyggden (vilket i sin tur kan ha en påverkan på ambulansens tillgänglighet) och ge ambulanspersonal möjlighet att välja ett mellansteg mellan att lämna kvar en patient i hemmet och att transportera den till en akutmottagning.  För att undersöka vilken påverkan en alternativ vårdväg kan ha på ambulanser sett till både tid och tillgänglighet, har en diskret händelsestyrd simuleringsmodell utvecklats. Denna modell har använts i en scenariostudie för att undersöka hur en alternativ vårdväg kan påverka ambulans och patienter på glesbygden. Data från SOS Alarm och Region Skåne har möjliggjort en generering av indata som bättre överensstämmer med verkligheten. Resultatet av scenariostudien tyder på att en alternativ vårdväg kan förbättra tillgängligheten för en ambulans på glesbygden genom att förkorta transporttiden till mottagande vårdinstans. / The need for emergency care has increased in recent years and has put increased pressure on the ambulance sector in general. How to improve and streamline different parts of the care chain is an issue that decision-makers in this sector constantly need to keep in mind in order to meet this need. There are visions of equal care for all people in our society, which unfortunately can be difficult to achieve in practice. People who live in sparsely populated areas usually experience longer waiting times to receive an ambulance than people in urban areas, and the transport time for these ambulance calls is longer because of the (usually) longer distance to the nearest emergency room. In addition, for ambulance personnel, it can in some cases be difficult to make a correct assessment of whether a less acute patient needs to be transported to an emergency department. A possible change in the care chain could be to transport less acute patients to a nearby health center instead of an emergency room - a so-called alternate route of care. This could result in both shorter transport times in sparsely populated areas (which in turn can have an impact on the availability of the ambulance) and give ambulance staff the opportunity to choose an intermediate step between leaving a patient at home and transporting it to an emergency department. To investigate the impact that an alternate route of care can have on the aspects of time and accessibility for ambulances, a discrete event-driven simulation model was developed. This model has been used in a scenario study to investigate how an alternate route of care can affect ambulances and patients in sparsely populated areas. Data from SOS Alarm and Region Skåne have made it possible to generate input data that better corresponds to reality. The results of the scenario study indicate that an alternate route of care can improve the accessibility of an ambulance in sparsely populated areas by shortening the transport times to the receiving care institution.

Studien presenterar hur Södra Wood kan applicera diskret händelsestyrd simulering (DES) genom modeller på sågverk för att bland annat öka produktionsvolym, förkorta ledtider och minska lagernivåer. Med hjälp av digitala verktyg som FACTS Analyzer simulerades önskade förändringar på produktionsflödet och även andra organisationella förändringar. Utfallet av de simulerade förändringarna resulterade i flertalet positiva slutsatser som kunde presenteras och även visualiseras. Bevisligen kan simuleringar användas som grund till diverse besulttaganden och vidare även till Proof-Of-Concept trots att aggregerade modeller används. Det finns dock mycket utrymme kvar till vidareutveckling av denna typ av arbeten där värdeflödet i industrier av denna domän kan gynnas väsentligt.