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Today, drones are used in both a civilian and military context, a swarm being a group of autonomous drones which are partly controlled by an operator. Swarms are a concept that is still in the research stage and previous research has consisted of how a swarm will communicate with the operator and how the swarm will work technically. However, the problem with the research available today is that it largely lacks the military connection. Hence, this study has aimed to investigate how the Armed Forces want to use swarms in the context of reconnaissance missions. The questions posed were, how do personnel within the Armed Forces want to plan swarm missions? What behaviors and capabilities do Armed Forces personnel want a swarm to possess? How do Armed Forces personnel want to receive information from swarms? Empirical data were collected by conducting three interviews with three individuals employed by the Armed Forces. The empirical data was then analyzed using qualitative content analysis where the responses were divided into smaller groups and sub-groups.  The study resulted in tables of desired abilities and behaviors that can be used in later research to create a real swarm system.

Secondhand ship is an option to improve marine business competitiveness. It provides a way for ship owners to integrate customer market rapidly without spending many resources on producing new ships. However, secondhand ships that perfectly suit owner's requirements becomes unavoidable challenge. Ship owners may decide to modify their ships to completely fulfill their requirements. A modification method that is often implemented is cargo replacement as observed from customer and global trends. It impacts ship stability due to different cargo properties which leads to different ship physical properties, such as position of center of gravity and buoyancy. Due to this impact, some ships may have excessive or reduced stability which causes potential damages. To ensure that cargo replacement does not negatively impact ship stability, it is evaluated according to the stability regulation of International Maritime Organization and classification society. A cement carrier vessel named MV Cemfjord is used as an example ship. The cargo is replaced from cement (ρ=1.35 tons/m3) to iron ore (ρ=3.03 tons/m3) and fly ash (ρ=0.794 ton/m3). Some modifications such as cargo position and total payload weight will be adjusted to some requirements. After implementing those modifications, some stability issues due to ship center of gravity shifting are considered. Therefore, the possibility of excessive and reduced stability may follow because of this effect. This study will investigate those stability issues and define the solution to overcome them. In this study, two solutions are offered. Firstly, the ship center of gravity is adjusted bymodifying the general arrangement. Other solution is conducted through adjusting the ship center of buoyancy by adding sponsons that affects buoyancy force on the ship hull. After defining the solution, it will be visualized into physical manners, in form of the new general arrangement or the sponsons dimension. Advantages and disadvantages of the chosen solution will also be discussed. / Andrahandsmarknaden för skepp är ett alternativ för sjöfartsindustrin att öka sin konkurrenskraft. Det ger möjligheten att etablera verksamheten på nya marknader utan att behöva bygga nya skepp. Utmaningen med detta är att hitta andrahandsskepp som kan möta kravspecifikationen som den nya ägaren ställer. En modifikation som ofta implementeras är byte av frakt gods för att tillgodose kunder och globala trender. Däremot påverkar lastens olika egenskaper stabiliteten i fartyget genom att masscentrum och flytkraftscentrum förskjuts. Detta är något som kan skada fartygen. För att undvika negativa konsekvenser från lastersättningen utreds den utifrån regler som är bestämda utav International Maritime Organization och klassificeringssällskap. Fartyget MV Cemfjord används som exempelskepp under den här studien. Ursprungligen är det ett fartyg som fraktar cement (ρ=1.35 ton/m3). I den här studien byts lasten ut till järnmalm (ρ= 3.03 ton/m3) och flyg aska (ρ=0.794 ton/m3). Modifikationer rörande lastpositionen och maximal lastkapacitet kommer göras för att möta vissa krav. Efter implementeringen kommer hänsyn tas till förskjutningen av fartygets masscentrum utifrån ett stabilitetshänseende. Studien kommer utreda och presentera lösningar för att komma till rätta med dessa problem. Två lösningar presenteras. Den första lösningen går ut på att flytta fartygets masscentrum genom att ändra fartygets generella layout. Den andra lösningen går ut på att förändra fartygets flytkraftscentrum. Detta görs genom att montera volymer på sidan av fartyget (eng. sponsons) som förändrar fartygets flytkraft. När lösningarna definierats kommer de visualiseras för att jämföra skillnader i fartygets yttre dimensioner. Fördelar och nackdelar med de två alternativen diskuteras också.

Volvo Construction Equipment is one of the leading construction machinery manufacturers in the world. To stay amongst the leaders, research and development projects for new technologies are crucial. The most important path of development today is the reduction of emissions produced by these heavy duty vehicles. To tackle this challenge, several technologies are already used in industry. One example are hybrid machines that combine a conventional diesel engine with batteries, resulting in reduced engine size and pollutants. Another option are full battery-electric vehicles, which can reduce the on-site emissions to zero. The electrochemical processes within batteries are however comparable slow and result in long recharge times. A new focus of development within the industry are hybrid systems combining fuel cells and batteries. Since hydrogen can be refueled almost as fast as convenient fuel, it solves the issue of long recharge times. Additionally, the reaction is emission free, since there is no combustion process and the only byproduct that is emitted from the fuel cell is chemically clean water. This thesis aims to propose an architecture and packaging solution to replace the diesel engine in a large size wheel loader with a fuel cell power system. This also includes all respective auxiliary systems, i.e. energy storage, cooling and electric systems. Achieving the same performance as a conventional large size wheel loader as well as keeping the spatial envelope the same are the main objectives of this work. To achieve these goals, an extensive study on the most common drive cycles is carried out to understand the power demand of the machine. After the selection of an energy storage system based on a MATLAB simulation script, a cooling system is modelled and scaled to fulfill the operating requirements of the different components. Eventually, all systems are modeled and installed into the wheel loader in CATIA V5. The study showed, that the new system architecture of the vehicle can be fitted into the existing engine bay with a slight extension of the rear frame and hood. Two power optimized batteries are combined with one fuel cell. Hydrogen tanks with a filling volume of 478 [L] can be installed in the machine, covering 50% of the customer population curve without degradation of performance. This includes one refill of the wheel loader during the day. The performance parameters match the conventional machine up to a high degree, concluding that the conversion of a large size wheel loader into a fuel cell powered wheel loader is feasible.

The engineering competition Formula Student has introduced a Driverless Vehicle (DV)class, which requires the students to develop a car that can autonomously make its wayaround a cone track. To ensure the safety of such a vehicle, an Emergency Brake System(EBS) is required. The EBS shall ensure transition to safe state for detection of a singlefailure mode. This thesis work covers the design of the EBS for KTH Formula Student(KTH FS).Due to the safety critical character of this system, the software part of the EBS, calledEBS Supervisor, has been analyzed in accordance with the safety standard ISO 26262 tosee if an improved safety could be achieved. The analysis has been perform according toPart 3: Concept phase of ISO 26262 with an item definition, Hazard Analysis and RiskAssessment (HARA), Functional Safety Concept (FSC) and Technical Safety Concept(TSC).The result of the analysis showed that the EBS Supervisor requires extensive redundanciesin order to follow ISO 26262. This includes an additional CPU as well as signal checksof inputs and outputs. Due to limited resources in terms of money and time within theKTH FS team, these redundancies will not be implemented. The process of working withthe safety standard did however inspire an increased safety mindset. / Ingenjörstävlingen Formula Student har introducerat en förarlös tävlingsklass (eng:Driverless Vehicle) som innebär att studenterna ska utveckla en bil som autonomt kan tasig runt en konbana. För att försäkra sig om säkerheten för ett sådant fordon krävs ettnödbromssystem (eng: Emergency Brake System (EBS)). EBS:en skall försäkra att enövergång till ett säkert tillstånd sker då ett singulärt fel upptäcks. Det här examensarbetetbehandlar designen av EBS:en för KTH Formula Student.På grund av den säkerhetskritiska karaktären hos detta system har mjukvarudelen avEBS:en, kallad EBS Supervisor, blivit analyserad utifrån säkerhetsstandarden ISO 26262för att se om en förbättrad säkerhet kunde uppnås. Analysen har blivit genomfördenligt Del 3: Konceptfas av ISO 26262 med item definition, Hazard Analysis and RiskAssessment, Functional Safety Concept och Technical Safety Concept.Resultatet av analysen visade att EBS Supervisor kräver omfattande redundanser föratt uppfylla ISO 26262. Detta inkluderar en extra CPU såväl som kontroller av inochutsignaler. På grund av begränsade resurser i form av pengar och tid inom KTHFS, valdes dessa redundanser att inte implementeras. Processen av att arbeta medsäkerhetsstandarden har dock inspirerat ett ökat säkerhetstänk.

The thesis focuses on investigating and optimizing a bushing script implemented as a tool in MSC ADAMS/Car. The study provides an insight on the representation of a rubber bushing and identify parameters which can be used to define the properties of a bushing in a simulation environment such as ADAMS/Car. The tool being studied here can be used to implement different kind of bushings such as a hydro bushing and a general rubber bushing, but optimization was implemented for the rubber bushing only. With an increasing reliance on Computer Aided Engineering (CAE) tools in the designing process, it is necessary that the vehicle behaviour can be predicted without relying on physical testing. CAE tools reduces the need of prototypes and provides a faster approach to designing vehicles. MSC ADAMS/Car is one such tool, which has been used here to predict the vehicle dynamic behaviour, which will influence the ride, handling and comfort characteristics of the vehicle. Rubber bushings, which have been studied here, have a significant contribution to the overall stiffness of the vehicle and as such, it is imperative that the tool being used here, is accurate and makes the designing process easy. The rubber bushing can be imagined to be a combination of a non-linear elastic spring, a frequency dependent Maxwell component and an amplitude dependent frictional element. In order to ease the design of the bushing properties, a reduced number of input properties are used to calculate the bushing properties internally. While trying to validate the force hysteresis loop obtained through the model with the measured data, it was seen that the accuracy was quite poor for the model when loading it with dynamic loads corresponding to amplitudes of0.2 mm and lower. The quasi-static loading and dynamic loading above 0.2 mm is shown to have a satisfactory accuracy when compared to the measured data.

The investment of space commerce is skyrocketing and it is predicted to be a nascent business in the future. The spacecraft demand has been growing not only for NASA and other space agency’s mission but also collaboration business between small space industries, academia, and scientific community. This glimpse brought an interest to a new investor, government, military, and manufacturing company to deliver their objectives efficiently. Nowadays, many startups compete embracing innovation and pioneering the novelty of space project beyond prodigious vision in an unprecedented way. Many players foresee that decreasing size of the rocket is an important key to survive and succeed in the space business. One of the efficient acts is lowering the launch cost. This can be achieved by designing a small size, lightweight and affordable spacecraft. Within this context, a Beyond Atlas Spacecraft which will be sent to Asteroid 2016-HO3, has achieved a wet mass of 20.85 kg with the size of 24.7 x 42.2 x 40.8 cm in stowed mode and 84 x 399 x 40.8 cm in unstowed mode. However, the drawback being light and small may lead to catastrophic failure due to resonance frequency events. According to past experience, the gyro of the Swedish national satellite was damaged during ground testing and it was suspected due to high amplification when the natural frequency coincides to the main structure resonance. Therefore, this work is focusing on a spacecraft development and a non-destructive structural analysis. The coupled-load analysis of a preliminary spacecraft design including sinusoidal, random vibration and shock analysis are calculated using FEM. This effort can reduce the risk of component destruction before laboratory testing as well as understand better the dynamic behavior of the spacecraft. The critical frequency in each orthogonal axis with base input from launch environment of the LM-3A Launch Vehicle was devised. The maximum stress, amplitude, and acceleration in accordance of qualification test criteria were evaluated and discussed. / Investeringen av rymdhandeln är skyrocketing och det förväntas bli en växande verksamhet i framtiden. Efterfrågan på rymdfarkoster har ökat inte bara för NASA och andra rymdorganisationens uppdrag utan även samarbete mellan små rymdindustrier, akademin och det vetenskapliga samfundet. Denna glimt väckte intresse för en ny investerare, regering, militär och tillverkningsföretag för att effektivt kunna leverera sina mål. Idag konkurrerar många startups om att omfatta innovation och banbrytande rymdprojektets nyhet bortom en fördärvad vision på ett aldrig tidigare skådat sätt. Många spelare förutser att minskad storlek på raketen är en viktig nyckel för att överleva och lyckas i rymdverksamheten. En av de effektiva handlingarna sänker lanseringskostnaden. Detta kan uppnås genom att utforma en liten storlek, lätt och prisvärd rymdfarkost. Inom detta sammanhang har en Beyond Atlas Spacecraft som skickas till Asteroid 2016-HO3, uppnått en våt massa på 20,85 kg med storleken 24,7 x 42,2 x 40,8 cm i stuvningsläge och 84 x 399 x 40,8 cm i ostoppat läge. Nackdelen som är ljus och liten kan emellertid leda till katastrofalt fel på grund av resonansfrekvenshändelser. Enligt tidigare erfarenhet skadades gyroen i den svenska nationella satelliten under marktestning och det misstänktes på grund av hög förstärkning när den naturliga frekvensen sammanföll med huvudstrukturen resonans. Därför fokuserar detta arbete på rymdskeppsutveckling och en icke-destruktiv strukturanalys. Den kombinerade belastningsanalysen av en preliminär rymdfarkostkonstruktion inklusive sinusformad, slumpvibration och chockanalys beräknas med användning av FEM. Denna insats kan minska risken för komponent förstörelse före laboratorietestning samt förstå bättre rymdskeppets dynamiska beteende. Den kritiska frekvensen i varje ortogonal axel med basinmatning från startmiljön för LM-3A-startkärlet utformades. Den maximala spänningen, amplituden och accelerationen i enlighet med kvalifikationstestkriterierna utvärderades och diskuterades.

A dominating source for the radiated acoustic noise from a train at low speeds is the traction motor. This noise originates from electromagnetic forces acting on the structure resulting in vibrations on the surface and thus radiated noise. It is often perceived as annoying due to its tonal nature. To achieve a desirable acoustic behavior, and also to meet legal requirements, it is of great importance to thoroughly understand the generation of noise of electromagnetic origin in the motor and also to be able to control it to a low level. In this work, experimental tests have been performed on a traction motor operated from pulse width modulated (PWM) converter. A PWM converter outputs a quasi-sinusoidal voltage created from switched voltage pulses of different widths. The resulting main vibrations at PWM operation and their causes have been analyzed. It is concluded that an appropriate selection of the PWM switching frequency, that is the rate at which the voltage is switched, is a powerful tool to influence the noise of electromagnetic origin. Changing the switching frequency shifts the frequencies of the exciting electromagnetic forces. Further experimental investigations show that the trend is that the resulting sound power level decreases with increasing switching frequency and eventually the sound power level reaches an almost constant level. The underlying physical phenomena for the reduced sound power level is different for different frequency ranges. It is proposed that the traction motor, similar to a thin walled cylindrical structure, shows a constant vibration over force response above a certain frequency. This is investigated using numerical simulations of simplified models. Above this certain frequency, where the area of high modal density is dominating, the noise reducing effect of further increasing the switching frequency is limited. / <p>QC 20180109</p>

The work in this thesis focuses on the use of explicit finite element analysis (FEA) in the modelling of fluid-structure interaction of panel-water impacts. Paper A, considers modelling of a two-dimensional rigid wedge impacting a calm water surface. From analytical methods and results of a systematic parameter study a generalised approach for determination of fluid discretization and contact parameters in the modelling of arbitrary hull-water impact situations is developed and presented. In paper B the finite element modelling methodology suggested in paper A is evaluated for elastic structures by a convergence study of structural response and hydrodynamic load. The structural hydroelastic response is systematically studied by a number of FE-simulations of different impact situations concerning panel deadrise, impact velocity and boundary conditions. In paper B a tentative method for dynamic characterization is also derived. The results are compared with other published results concerning hydroelasticity in panel water impacts. The long-term goal of this work is to develop design criteria, by which it can be determined whether the loading situation of a certain vessel type should be regarded as quasi-static or dynamic, and which consequence on the design a dynamic loading has. / QC 20101126

This thesis report presents a study on the virtualization of an Electric Cabin Scooter used to validate the feasibility of converting it into an autonomous vehicle. The project aimed to design, develop, and test a virtual model of the car that can navigate from points A to B while avoiding obstacles. The report describes the methodology used in the project, which includes setting up the workspace, construction of the virtual model, implementation of ROS2 controllers, and integration of SLAM and Navigation2. The thesis report also describes and discusses related work, as well as the theoretical background of the project. Results show a successfully developed working virtual vehicle model, which provides a solid starting point for future work. / Detta examensarbete presenterar en studie om virtualiseringen av en elektrisk kabinscooter. Den virtuella modellen används för att validera genomförbarheten av att omvandla den till ett autonomt fordon. Projektet syftade till att designa, utveckla och testa en virtuell modell av bilen som kan navigera från punkt A till B medan den undviker hinder. Rapporten beskriver metodiken som används i projektet, vilket inkluderar att sätta upp arbetsytan, konstruktion av den virtuella modellen, implementering av ROS2-kontroller och integration av SLAM och Navigation2. Rapporten diskuterar även relaterat arbete, samt teoretisk bakgrund till arbetet. Resultaten visar en framgångsrikt utvecklad fungerande virtuell fordonsmodell, som ger en solid utgångspunkt för framtida arbete.