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Development, operation, and testing of a heuristic line balancing program for a microcomputer are discussed. Tasks are grouped into work stations along an assembly line such that the number of work stations required is minimized. The model is built primarily using the Hoffman (1963) procedure with modifications described by Gehrlein and Patterson (1975). For purposes of comparison the Rank Positional Weight technique (Helgeson and Birnie, 1961) is also included in the model. Testing included thirty-seven different balances using problems from the literature. For each balance, both Rank Positional Weight and Hoffmann solutions were obtained in the forward and reverse directions. Four measures of performance were considered in this study. These measures of performance were: (1) the average percentage a balance is above the optimum solutions, in terms of number of stations; (2) time to obtain a balance; (3) the best solution in terms of the lowest number of stations and lowest standard deviation of the slack times; and (4) the largest value of minimum station slack time. Overall it was found that the Hoffmann procedure with a delay factor if 1.5 was best suited for the microcomputer application. Further work is recommended to find the optimum delay factor and apply the Modified Hoffmann procedure to solving line balancing problems where the cycle time is minimized given a set of work stations.

Detta arbete har utförts inom ett projekt på Scania, Södertäljes chassimontering. Scania genomgår nu en omställning till elektrifierade lastbilar. För att göra den här omställningen krävs det förstudier på hur monteringar för nya komponenter kan se ut. Det här arbetet fokuserar på en förmontering som ingår i Scanias omställning, där målet är att ta fram ett koncept av montering och layout med rätt nivå av säkerhet, kvalitet och leveranssäkerhet i en arbetsmiljö som är hållbar över tid. Ett annat mål med det här examensarbetet är att undersöka vilka metoder och analyser som används i samband med framtagning av layout, balansering och riskanalys och jämföra det med hur det funkar på Scania. Eftersom det är en förstudie har arbetet fokuserat på att fånga kapaciteten av ett maximalt scenario samt även undersökt ett mindre scenario för att analysera flexibiliteten i den framtagna lösningen. Resultatet från detta arbetet är att Scania arbetar mycket från erfarenhet kompletterat med teoretiska metoder och i nära samarbete med påverkade gränssnitt för att ta hänsyn till många olika delar samt se helheten. Andra resultat från det här arbetet är en konceptlayout presenterad i AutoCAD och en balanserad monteringssekvens gjord i Avix. På grund av sekretess är bara delar av leveranserna till Scania presenterade i denna rapport. Det resultat som presenteras är centrerat runt en station, benämnd station X. Slutsatsen från arbetet är att teoretiska metoder ofta behöver kompletteras med erfarenhet, eftersom verkligheten är mer komplex än vad de teoretiska metoderna kan fånga. Scanias klimatomställningsplan är enligt författarna utarbetad och omställningen är ett drivande fokus inom företaget. Författarna ser stor potential i att Scania ska nå sina hållbarhetsmål. / This thesis was conducted within a project at Scania, Södertälje Chassi Assembly. Scania is currently going through a transformation towards electrified transport solutions. This transformation leads to a need of new products, and therefore a need of prestudies for new assembly lines. The focus of this thesis is on one preassembly being part of Scanias transformation, where the goal is to deliver a concept of assembly and layout with the right amount of safety and quality in a lasting working environment. Another goal is to look into what methods and techniques that are used within the development of layout, balancing and risk assessment, and to compare these with what is implemented at Scania. Since this thesis carries through a prestudie, the work has been investigating a worst case scenario, regarding the maximum capacity of the preasembly. A lower scenario has also been looked into, in order to explore the flexibility of the suggested preassembly. The result of the thesis work and the delivery to Scania was a conceptual layout in AutoCad and a balanced assembly sequence in Avix. Due to sensitive material, parts of these deliveries are presented in the report, these parts are centered around one of the assembly stations, station X. Regarding the comparison it was found that Scania works a lot based on experience, complemented with theoretical methods, having close cooperation with near interfaces in order to intercept many aspects and achieve an holistic view. One concluding note of the thesis, is that the theoretical methods often need to be complemented with experience, since the reality is complex and has more interfaces than what is captured with the methods and techniques. The sustainability plan of Scania is well worked through and it is a driving focus for the company, which the authors see as a great potential for Scania in order to reach their climate targets.

Modeling and Implementation of a Hardware Efficient Low-Voltage-To-Cell Battery Balancing Circuit for Electric Vehicle Range Extension / One disadvantage of electric vehicles is their limited driving range when compared to internal combustion engine vehicles. Battery packs are also a significant cost to electric vehicle manufacturers, and lithium-ion battery cells must remain within controlled voltage limits. Thus, the requirements for the electric system are to be cost effective, perform battery management, and make it as efficient as possible to increase its range. Battery packs are typically constructed from around 100 battery cells in a series connection. During use of an electric vehicle, the battery cells become mismatched due to small differences in capacity. This effect is further amplified as the electric vehicle ages. Diverging cells cause issues during driving, since weak cells can limit the useable capacity of the vehicle. In order to use the whole capacity of the battery pack, and thus the entire range of the electric vehicle, the cells should be balanced. Strong cells should distribute their excess capacity to weaker cells during driving. The thesis presents the design, modeling and implementation of a novel hardware-efficient battery balancing circuit. First, the theory behind battery balancing is presented. Next, existing battery balancing circuits are compared. Finally, the proposed battery balancing circuit is discussed. The design of the proposed topology is examined in detail. Simulations show that the circuit transfers energy between non-adjacent cells throughout the entire pack. Experimental work is performed on two custom printed circuit boards, a 12 cell lithium-ion module, and a 12V lead acid battery. The results confirm the function of the prototype. The effect of the battery balancing circuit on driving range is examined with vehicle modeling simulations. A 2018 Chevrolet Bolt model is produced and capacity differences are given to each cell. The proposed topology balances the cells while driving, extending driving range on UDDS and HWFET drive cycles. / Thesis / Master of Applied Science (MASc) / One disadvantage of electric vehicles is their limited driving range when compared to internal combustion engine vehicles. Thus, there is a requirement to make the electric system as efficient as possible in order to increase its range. A large piece of the electric system includes the battery pack. Battery packs are typically constructed from around 100 battery cells in a series connection. During use of an electric vehicle, the battery cells become mismatched. This effect is also amplified as the electric vehicle ages. In order to use the whole capacity of the battery pack, and thus the entire range of the electric vehicle, the cells should be balanced. The thesis presents the design, modeling and implementation of a novel hardware efficient battery balancing circuit. The effect of the battery balancing circuit on driving range is examined.