This thesis work presents a model predictive control (MPC) based trajectory planner forhigh speed lane change and low speed parking scenarios of autonomous four wheel steering(4WS) vehicle. A four wheel steering vehicle has better low speed maneuverabilityand high speed stability compared with normal front wheel steering(FWS) vehicles. TheMPC optimal trajectory planner is formulated in a curvilinear coordinate frame (Frenetframe) minimizing the lateral deviation, heading error and velocity error in a kinematicdouble track model of a four wheel steering vehicle. Using the proposed trajectory planner,simulations show that a four wheel steering vehicle is able to track different type ofpath with lower lateral deviations, less heading error and shorter longitudinal distance. / I detta avhandlingsarbete presenteras en modellbaserad prediktiv kontroll (MPC) -baseradbanplaneringsplan f¨or h¨oghastighetsbanan och l°aghastighetsparametrar f¨or autonomtfyrhjulsdrift (4WS). Ett fyrhjulsdrivna fordon har b¨attre man¨ovrerbarhet med l°ag hastighetoch h¨oghastighetsstabilitet j¨amf¨ort med vanliga fr¨amre hjulstyrningar (FWS). MPC-optimalbanplanerare ¨ar formulerad i en kr¨okt koordinatram (Frenet-ram) som minimerar sidof¨orl¨angningen,kursfel och hastighetsfel i en kinematisk dubbelsp°armodell av ett fyrhjulsstyrda fordon.Med hj¨alp av den f¨oreslagna banaplaneraren visar simuleringar att ett fyrhjulsstyrfordonkan sp°ara olika typer av banor med l¨agre sidof¨orl¨angningar, mindre kursfel ochkortare l¨angsg°aende avst°and.

In this thesis, support structures of a polymer powder based process called XXXXXXXX™ are examined. These structures are crucial for most additive manufacturing processes. The effects of several factors on five industrially important characteristics of support structures are examined by use of the Design of Experiment (DoE) method. It describes the planning as well as the analysis of the experiments. The experiments are planned in a fractional factorial 211-5 design with 64 specimens, resulting in a resolution of IV. The analysis of the data is done by use of the ANOVA method, with which the significance of effects and interaction effects are checked. / I detta examensarbete undersöks stödstrukturer för en polymer-pulverbaserad process kallad XXXXXXXX. Dessa strukturer är väsentliga för de flesta aditiv tillverkning. Med hjälp av metoden "Design of Experiment" (DoE) undersöks effekten av flera faktorer på fem industriellt viktiga egenskaper för stödstrukturer. DoE beskriver både planeringen och analysen av experiment. Experimenten planeras i en fraktionerad faktoriell 211-5 design med 64 provexemplar vilket resulterar i en upplösning av IV. Dataanalysen genomförs med hjälp av ANOVA-metoden, med vilken signifikansen av effekter och interaktionseffekter kan undersökas.

In most application to date reinforced carbon fiber composites have been used in relatively smaller thickness, less than 10mm thick and essentially for carrying in-plane loads. As a result, design and testing procedures were developed which reflected the need to understand the in-plane response of the material. recently, engineers and designers have begun to use reinforced carbon fiber composites in thicker sections, where an understanding of the through-thickness response is of para-mount importance in designing reliable structures, particularly where the through-thickness strength has a controlling influence on the overall structural strength of the component. In this thesis tests will be done on carbon fiber non-crimp fabric (NCF) which will be loaded in compression and shear and elastic moduli and strength will be evaluated. In characterizing the through-thickness mechanical properties of a composite, the objective is to produce a state of stress in the test specimen which is uniform and will repeatedly measure the true properties with accuracy. In this study, specimens were machined from two blocks of thick (~20 mm) laminates of glass/epoxy and NCF carbon fiber infused with vinylester and tested in compression, and shear.

This thesis investigated the impact performance of CFRP products within the sports industry. The primary aim of this thesis was to evaluate different configurations, matrix system, and technologies to find the best performing solutions for impact. During this work, an extensive literature study was conducted and various solutions were reviewed. Further on, several tubes were manufactured, impacted and put through a 2 point bending test to find out the residual strength. It was found that TeXtreme R fabrics positively affected the impact performance when compared to conventional fabrics and UD depending on the placement location. Thin plies proved to be better than conventional plies. Newer technologies such as CNT stitching requires further investigation before it can be qualitatively assessed.

For a successful design of an engineering system it is essential to pay careful attention to its dynamic response. This is particularly true, in the case of nonlinear systems, since they can exhibit very complex dynamic behaviour, including multiple co-existing stable solutions and chaotic motions, characterized by large sensitivity to initial conditions. In some systems nonlinear characteristics are desired and designed for, but in other cases they are unwanted and can cause fatigue and failure. A type of dynamical system which is highly nonlinear is discontinuous or non-smooth systems. In this work, systems with impacts are primarily investigated, and this is a typical example of a discontinuous system. To enhance or optimize the performance of dynamical systems, some kind of control can be implemented. This thesis concerns implementation of low-cost control strategies for discontinuous systems. Low-cost control means that a minimum amount of energy is used when performing the control actions, which is a desirable situation regardless of the application. The disadvantage of such a method is that the performance might be limited as compared with a control strategy with no restrictions on energy consumption. In this work, the control objective is to enforce a continuous or discontinuous grazing bifurcation of the system, whichever is desirable. In Paper A, the dynamic response and bifurcation behaviour of an impactoscillator with dry friction is investigated. For a one-degree-of-freedom model of the system, analytical solutions are found in separate regions of state space. These are then used to perform a perturbation analysis around a grazing trajectory. Through the analysis, a condition on the parameters of the system is derived, which assures a continuous grazing bifurcation. It is also shown that the result has bearing on the dynamic response of a two-degree-of-freedom model of the system. A low-cost active control strategy for a class of impact oscillators is proposed in Paper B. The idea of the control method is to introduce small adjustments in the position of the impact surface, at discrete moments in time, to assure a continuous bifurcation. A proof is given for what control parameters assures the stabilization. In Paper C, the proposed low-cost control method is implemented in a quarter-car model of a vehicle suspension, in order to minimize impact velocities with the bumpstop in case of high amplitude excitation. It is shown that the control method is effective for harmonic road excitation. / QC 20101118

With this contribution to the AVT-113/VFE-2 task group it was possible to prove the feasibility of high Reynolds number CFD computations to resolve and thus better understand the peculiar dual vortex system encountered on the VFE-2 blunt leading edge delta wing. Initial investigations into this phenomenon seemed to undermine the hypothesis, that the formation of the inner vortex system relies on the laminar state of the boundary layer at separation onset. As a result of this research, this initial hypothesis had to be expanded to account also for high Reynolds number cases, where a laminar boundary layer status at separation onset could be excluded. Furthermore, the data published in the same context shows evidence of secondary separation under the inner primary vortex. This further supports the supposition of a different generation mechanism of the inner vortical system other than a pure development out of a possibly laminar separation bubble. The unsteady computations performed on numerical grids with different levels of refinement led furthermore to the establishment of internal guidelines specific to the DES approach. / QC 20101111

Welded structures susceptible to weld deformations require sequent processing to allow for mounting of precision components. This thesis includes a case study of the rear axle mount on a Volvo L220 wheel loader. A product development process was deployed in order to explore and evaluate alternative mounting methods such that manufacturing cost due to sequent processing could be decreased. Analysis of the frame variations showed any new concepts has to accommodate variations of up to $\delta z=-1.24\pm3.5$ mm. The product development process found two potential concept philosophies; transferring concepts which improves upon the current concept by transferring the processing away from the frame onto smaller components that are cheaper to process, and absorbing concepts that avoids sequent processing by absorbing the frame variations altogether. The transferring concept "Custom Plate" was selected for further development. The concept is based on the principals of reverse engineering by manufacturing a custom plate from a 3D surface map of the deformed mounting surface, placed between the frame and rear axle bridge, matching the surface geometry of both entities. The concept showed no apparent critical strength issues when simulated in CATIA V5. However, the economical gain of the concept is slim and depends heavily what spaces can be allocated for additional processing machinery. Suggestions for further development of the concept are given along with a discussion of improvements outside of the system boundary of the project, such as simulation of welds and welding sequence, and collection, storing, analysis, and visualisation of data.

Stora transportköpare visar ett stort intresse för att använda eldrivna lastbilar och på så sätt minska koldioxidutsläpp och främja en renare miljö. Detta medför en ökad förbrukning av elektrisk energi, vilket kräver expansion av elnäten för att klara av den ökade belastningen. Borås Elnät ansvarar för eldistributionen i centrala Borås och omkringliggande områden och vill undersöka hur expansion av elnätet kan påverkas av en ökad belastning från eldrivna tunga fordon. Syftet med denna projektrapport är att identifiera framtida laddningsbehov, påverkan på elnätet och eventuella åtgärder. Metoden bestod av tre delar för att ta fram resultatet. Först undersöktes nuläget gällande tungafordon i Viared, sedan nuläget för eldrivna lastbilar och till sist om nuvarande elnät kan hantera den eventuella extra belastning som kan tillkomma från eldrivna lastbilar. Tre framtidsscenarier studerades för att få fram den eventuella belastningen. Dessa framtidsscenarier baserades på fem, tio och tjugo år fram i tiden. Informationen inhämtades genom möten med företag och dialoger med branschaktörer, samt genom att studera befintlig forskning och litteratur. En uppskattad andel av eldrivna fordon i fordonsflottan togs fram med hjälp av tillgänglig information. Denna information användes för att utveckla en generell bild av framtiden för elektriska fordon i Viared. Resultatet pekar på en ökning av eldrivna fordon för samtliga tre scenarion där andelen eldrivna fordon i fordonsflottan ökar med tiden. Detta kan komma att påverka elnätet i Viaredgenom att den högsta förväntade strömmen som kan uppstå är högre än vad de nuvarande kablarna klarar. Toppeffekten som kan uppstå i transformatorstationen börjar också nå nivåer som kan peka på att åtgärder behöver göras. / Large transportation buyers show a great interest in using electric trucks to reduce carbondioxide emissions and promote a cleaner environment. This entails an increased consumption of electrical energy, which requires the expansion of electrical grids to handle the increased load. Borås Elnät is responsible for the electricity distribution in central Borås and surrounding areas and wants to investigate how the expansion of the electrical grid can be affected by an increased load from electric heavy vehicles. The purpose of this project report is to identify future charging needs, the impact on the electrical grid, and possible measures. The method consisted of three parts to obtain the results. First, the current situation regarding heavy vehicles in Viared was examined, then the current situation for electric trucks, and finally whether the existing electrical grid can handle the potential additional load from electric trucks. Three future scenarios were studied to determine the potential load. These scenarios were based on five, ten, and twenty years into the future. Information was gathered through meetings with companies and dialogues with industry stakeholders, as well as studying existing research and literature. An estimated share of electric vehicles in the vehicle fleet was determined using available information. This information was used to develop a general picture of the future of electric vehicles in Viared. The results indicate an increase in electric vehicles for all three scenarios, where the proportion of electric vehicles in the vehicle fleet increases over time. This may impact the electrical grid in Viared, as the highest expected current that can occur exceeds what the current cables can handle. The peak power that can occur at the transformer station is also reaching levels that may indicate the need for action.

Formula Student is a global engineering competition where university students collaborate to design, construct, and race formula-style cars. Aerodynamics is one aspect in the vehicle design that can improve on-track performance by increasing cornering and straight-line speed. To improve the aerodynamics of KTH Formula Student's DeV18 vehicle, the side structure is being redesigned. The current model, DeV17, features an underperforming tunnel-based side structure. To address this issue, this had the goal to investigate a new multi-element wing design that utilizes ground effect. The design study of the DeV18 vehicle is conducted using Siemens NX 2212 for 3D modelling and Simcenter Star-CCM+ 17.06.008-R8 for airflow simulations. To quickly investigate certain design parameters effect on the results, Design Manager Project inside Simcenter Star-CCM+ is used. The resulting side structure produces a total of 26 N of downforce and 6 N of drag at 40 kph, more than twice that of DeV17’s side structure while also producing less drag. Although this significant improvement compared to DeV17, it is believed that further increases in performance are necessary to compete with top teams. By using a more sophisticated method to optimize the multi-element wing, such as adjoint optimization, the concept could be improved. However, the overall potential of the concept is still considered too limited to achieve the desired performance goals, which is why it will no longer be investigated further.

The railway vehicles are an increasing mean of transportation due to, its reduced impact on environment and high level of comfort provided. These reasons have contributed to settle a positive perception of railway traffic into the European society. In this upward context, the railway industrial sector tackles some important challenges; maintaining low operational costs and controlling the nuisance by-products of trains operation, the most important being railway noise. Track dynamic plays a main role for both issues, since a significant part of the operational costs are associated with the track maintenance tasks and, the noise generated by the track can be dominant in many operational situations. This explains why prediction tools are highly valued by railway companies. The work presented in this licentiate thesis proposes methodologies for accurate and efficient modelling of railway track dynamics. Two core axes have led the development of this task, on one hand, the rail modelling and, on the other hand, the characterisation of the finite length nature of track supports. Firstly, concerning the rail modelling technique, it has evolved under two major premises. On one hand, regarding the frequency domain, it should describe high frequency behaviour of the rail. In order to accomplish with this first premise, a model based on Timoshenko beam theory is used, which can accurately account for the vertical rail behaviour up to 2500 Hz. On the other hand, with respect to the time domain, the response should be smooth and free of discontinuities. This last condition is fulfilled by implementation of the Timoshenko local deformation. Secondly, a model of support that considers its finite length nature is sought. For this purpose, a Timoshenko element over elastic foundation is formulated. Thus, the common model of support, which is based on a concentrated connection, is substituted by a distributed model of support. In this way, several enhancements are achieved; the temporal contact force response is smoothed and a more realistic shape is obtained, the amplitude of the displacement due to the parametric excitation is reduced and the magnitude associated to the ‘pin-pin’ frequency is not overestimated. / <p>QC 20170522</p>