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  • 1.
    Agebro, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Nilsson, Andreas
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Driver preferences of steering gear ratio and steering wheel effort: A driving simulator study2006In: Proceedings of the FISITA World Automotive Congress, Yokohama, Japan 2006., 2006Conference paper (Refereed)
    Abstract [en]

    When driving an automobile, the driver has to correct the course as a result of road curvature and external disturbances. In order to make the vehicle both controllable and comfortable to drive, it is important that the steering system is designed with different drivers in mind. In this work, driver preferences of steering system characteristics is investigated by comparing standard steering wheel settings with unconventional steering gear ratio and steering wheel effort. The investigation is made using 18 test subjects in a moving base driving simulator. The evaluation includes two scenarios. In the first scenario the driver is overtaking a bus at 110 km/h when meeting traffic in the opposite lane. In the second scenario the driver is doing a manoeuvre by following a cone track at 55 km/h. To investigate if there are differences in preference of drivers with varying experience of driving, the drivers are chosen to either be low or high mileage drivers. People that drive less than 5,000 km/year are considered to be low mileage drivers, and people that drive more than 25,000 km/year are considered to be high mileage drivers.

    The results show that original settings of a typical passenger car, which served as reference, prove to display favourable characteristics compared to the unconventional settings investigated. However, there might be settings within the investigated intervals that can be considered superior. A distinct trend in the results is that increasing effort will lead to increased perceived stability, independent of ratio. High mileage drivers find the setting with low ratio and reference effort to possess better qualities than the reference when evaluating the attributes steering wheel force and response and only slightly less favourable properties than the reference when evaluating the attribute stability. High mileage drivers display a more distinct opinion and a higher sensitivity when evaluating the attributes. Despite the differing setup of the scenarios, many similarities can be observed when studying the results. Even though there are similarities in the results both between the scenarios and the categories of drivers, a study of the individual test subjects´ preferences reveal that several drivers prefer other settings than the reference for the investigated scenarios. Therefore, it is clear that the driver-vehicle system would benefit from tailoring the steering characteristics to the situation and driver.

  • 2.
    Agrawal, Harshit
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Gustafsson, Jacob
    Investigation of active anti-roll bars and development of control algorithm2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Active anti-roll bars have recently found greater acceptance among premium car manufacturers and optimal application of this technology has emerged as an important field of research. This thesis investigates the potential of implementing active anti-roll bars in a passenger vehicle with the purpose of increasing customer value. For active anti-roll bars, customer value is defined in terms of vehicle’s ride comfort and handling performance. The objective with this thesis is to demonstrate this value through development of a control algorithm that can reflect the potential improvement in ride comfort and handling. A vehicle with passive anti-roll bars is simulated for different manoeuvres to identify the potential and establish a reference for the development of a control algorithm and for the performance of active anti-roll bars. While ride is evaluated using single-sided cosine wave and single-sided ramps, handling is evaluated using standardized constant radius, frequency response and sine with dwell manoeuvres.The control strategy developed implements a combination of sliding mode control, feed forward and PI-controllers. Simulations with active anti-roll bars showed significant improvement in ride and handling performance in comparison to passive anti-roll bars. In ride comfort, the biggest benefit was seen in the ability to increase roll damping and isolating low frequency road excitations. For handling, most significant benefits are through the system’s ability of changing the understeer behaviour of the vehicle and improving the handling stability in transient manoeuvres. Improvement in the roll reduction capability during steady state cornering is also substantial. In conclusion, active anti-roll bars are undoubtedly capable of improving both ride comfort and handling performance of a vehicle. Although the trade-off between ride and handling performance is significantly less, balance in requirements is critical to utilise the full potential of active anti-roll bars. With a more comprehensive control strategy, they also enable the vehicle to exhibit different driving characteristics without the need for changing any additional hardware.

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  • 3.
    Ahlberg, Max
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Optimization based trajectory planning for autonomous racing2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Autonomous driving is one of the three new technologies that are disrupting the classical vehicle industry together with electrification and connectivity. All three are pieces in the puzzle to drastically reduce the number of fatalities and injuries from traffic accidents but also to reduce the total amount of cars, reduce the polluting greenhouse gases, reduce noise pollution and completely eliminate unwanted driving. For example would most people rather rest, read or do anything else instead of driving in congested traffic. It is not small steps to take and it will have to be done incrementally as many other things. Within the vehicle industry racing has always been the natural place to push the boundaries of what is possible. Here new technologies can be tested under controlled circumstances in order to faster find the best solution to a problem.Autonomous driving is no exception, the international student competition ”Formula Student” has introduced a driverless racing class and Formula E are slowly implementing Robo Race. The fact that race cars aim to drive at the limits of what is possible enable engineers to develop algorithms that can handle these conditions even in the every day life. Because even though the situations when normal passenger cars need to perform at the limits are rare, it is at these times it can save peoples lives. When an unforeseen event occurs and a fast manoeuvre has to be done in order to avoid the accident, that is when the normal car is driving at the limits. But the other thing to take into considerations when taking new technology into the consumer market is that the cars cannot cost as much as a race car. This means simpler computers has to be used and this in turn puts a constraint on the algorithms in the car. They can not be too computationally heavy.In this thesis a controller is designed to drive as fast as possible around the track. But in contrast to existing research it is not about how much the limit of speed can be pushed but of how simple a controller can be. The controller was designed with a Model Predictive Controller (MPC) that is based on a point mass model, that resembles the Center of Gravity (CoG) of the car. A g-g diagram that describes the limits of the modeled car is used as the constraints and the cost function is to maximize the distance progressed along the track in a fix time step. Together with constraints on the track boundaries an optimization problem is giving the best possible trajectory with respect to the derived model. This trajectory is then sent to a low level controller, based on a Pure Pursuit and P controller, that is following the predicted race trajectory. Everything is done online such that implementation is possible. This controller is then compared and evaluated to a similar successful controller from the literature but which has a more complicated model and MPC formulation. The comparison is made and some notable differences are that the point mass model is behaving similar to the more complex model from the literature. Though is the hypothesis not correct since the benefits of the simplification of the model, from bicycle to point mass model, is replaced when more complex constraints has to be set up, resulting in similar performance even in computational times.A combination of the two models would probably yield the best result with acceptable computational times, this is left as future work to research.

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  • 4.
    Akner, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    A method to generate drive cycles from operational data2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates the possibility to develop a method to generate drive cycles for heavy duty vehicles for Scania’s customers. A representative drive cycle is important to simulate realistic driving of vehicles. Trucks that are sold by Scania and other manufacturers are collecting data which are logged from the vehicle’s on-board computer during operations. This data is used for the development of new trucks, and the idea is that with operational data, a drive cycle can be generated which is representative for the operations of a specific truck. The developed methodology generates a drive cycle which is compared against this operational data. By making a first selection of already existing drive cycles and modifying the closest drive cycle to a selection of parameters, a drive cycle which corresponds to the operations of the specific truck can be designed. To compare against the operational data, simulations of the truck performing the drive cycle are conducted, and the results are compared to the truck’s operational data. The simulation tool is an internally developed model at Scania which has been verified against test measurements on trucks. A final methodology to generate drive cycles are developed and it compares the simulated fuel consumption and engine load matrix against operational data. By redesigning the drive cycle in an iterative process, results from simulation of the drive cycle becomes very similar to the operational data.

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  • 5.
    Angelis, Stavros
    et al.
    Volvo Car Corporation.
    Tidlund, Matthias
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Leledakis, Alexandros
    Volvo Car Corporation.
    Lidberg, Mathias
    Chalmers university of technology.
    Nybacka, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Katzourakis, Diomidis
    Optimal Steering for Double-Lane Change Entry Speed Maximization2014In: Proceedings of ACEV'14 International symposium on advanced vehicle control, 22-26 September 2014,Tokyo, Japan, Tokyo, Japan: Society of Automotive Engineers, 2014Conference paper (Refereed)
    Abstract [en]

    This study introduces a method for estimating the vehicle’s maximum entry speed for an ISO3888 part-2 double-lane change (DLC) test in simulation. Pseudospectral collocation in TOMLAB/ PROPT calculates the optimal steering angle that maximizes the entry speed. The rationale is to estimate the vehicle’s performance in the design phase and adapt the tuning to improve DLC ratings. A two-track vehicle dynamics model (VDM) employing non-linear tires, suspension properties and a simplified Dynamic Stability and Traction Control (DSTC) system was parameterized as a 2011 T5 FWD Volvo S60 using in-field tests and its corresponding kinematics and compliance (K&C) measurements. A sensitivity analysis on the parameters revealed certain trends that influence the entry speed, which can be varied from 69.4 up to 73.3 km/h when adapting certain vehicle features. To evaluate the method, the generated optimal steering control inputs for the simulated S60 were applied on the actual car motivating the further development of the method. 

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  • 6.
    Arbuthnott, Andrew
    et al.
    Uneå University.
    Hannibal, Martin
    University of Southern Denmark.
    Nybacka, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Renewing industry cluster development via interregional industry-university links2011In: International Journal of Innovation and Regional Development, ISSN 1753-0679, Vol. 3, no 6, p. 604-631Article in journal (Refereed)
    Abstract [en]

    The importance of developing regional industry clusters has grown alongside the need for industries and universities to be more interlinked. A regional automotive testing industry cluster, located in the north of Sweden, is the innovative empirical setting for this research paper. Following the logic of induction, it is discovered that as the regional industry reached a certain maturity, renewal was sought via developing links to universities within other regions in Sweden. A conceptual sensemaking lens is used to theorise upon the links thus formed and to develop new insights into regional industry renewal processes and interregional industry-university links. Practical insights stemming from the case are also explained, and future research directions provided.

  • 7.
    Asher, Mohit Hemant
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Lönnergård, Alexander
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Objective evaluation of vehicle handling during winter conditions2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Vehicle handling evaluation is a crucial part of the vehicle development process. The evaluation can be done in two ways, subjectively; by expert test drivers or objectively; by performing repeatable standard manoeuvres usually by steering robots. Subjective testing is resource intensive as prototypes need to be built. Objective testing is less so, as it can be performed in a virtual environment in conjunction with physical testing. In an e˙ort to reduce resources and time used in vehicle development, manufacturers are looking to objective testing to assess vehicle behaviour.Vehicle handling testing in winter strongly relies on subjective testing. This thesis aims to investigate into the usage of objective test strategy to assess vehicle handling behaviour in winter conditions. Manoeuvres and metrics are defined for summer con-ditions, but not for winter. Hence the goal was to define new or modified metrics and manoeuvres custom to winter testing.Data from an objective winter test was obtained and analysed. The manoeuvres used were constant radius (CR), frequency response (FR), sine with dwell (SWD) and throt-tle release in turn (TRIT). The manoeuvres were compared to public standards from the International Organization for Standards (ISO) and National Highway Traÿc Safety Administration (NHTSA) as well as the vehicle manufacturer standards.The data from a reference vehicle is compared to that from three configuration vehicles, one without anti-roll bar in the front, one without rear anti-roll bar and a standard. The di˙erence in the signals between reference and configuration vehicles is compared to the spread in data of the reference vehicle to determine the signal-to-noise ratio in the manoeuvres. The spread of reference data is analysed to determine the distribu-tion and to di˙erentiate between the two test days. To replicate vehicle behaviour in simulation, winter tyre models using brush and Magic Formula model equations were investigated. These were used in a bicycle and a VI-CarRealTime model. The perfor-mance of these are checked and compared. The bicycle model is used in an unscented Kalman filter, to investigate potential improvements in signal processing. The metrics obtained from the study of standards are checked for robustness in winter conditions by analysis of variance (ANOVA) methods. The procedure of selection of metrics from the ANOVA results is explained. Further, the manoeuvres are modified virtually in VI-CarRealTime, from the results of a sensitivity analysis. The di˙erence in metrics between reference and configuration vehicles is maximized.The final results of the thesis were; a test plan with modified manoeuvres and a set of robust metrics. Also containing important information to aid in the execution of the tests. The conclusions drawn were that the noise in winter testing is high, but the di˙erence between vehicles is statistically significant for some robust metrics. The metrics related to yaw rate were in general more robust. Open-loop throttle and steering control in manoeuvres should be avoided as far as possible. A bicycle model is not complex enough to represent vehicle behaviour at high slip angles. Performance increase of a UKF is not justified as to the e˙ort involved.

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  • 8.
    Bartos, Elias
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Ahlberg, Kristian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Minimizing of Drain Leakage on a Scania Retarder2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To enhance the drivability and increase safety a major part of Scania’svehicles is fitted with a retarder. The retarder is a complementary brake system that assists the vehicles mechanical brakes. When running a retarder some oil leakage can occur. The main source to the leakage is oil sump ventilation but there is also some contribution from the solenoid valve block that controls the retarder. Test results from the test rig shows that with rather simple methods the oil leakage in form of oil mist can be captured. The efficiency of for instance concept 1 with half the volume and a chicane interior was as high as 99 to 100 %. For the concept 2 with the expanded metal filter the efficiency was in the order of 96 to 100 %. From testing it has also become clear that there is a problem to feed the oil back into the oil sump. Initial tests shows that the retarder is rather sensitive regarding the placing of the feedback channel. It is considered that the best option is to only use the feedback channel that enters the internal drain of the retarder. Measurements show that the airflow in the tube from the accumulator could reach velocities up to 67 m/s. It is considered that the best solution is to have two separate chambers, one for the accumulator and one for the oil sump ventilation, the safety valve and the proportion valve. The reason for this is that the combination of oil in a chamber together with high airflow from the accumulator is disastrous and the retarder leaks far worse compared to original. The conclusion is therefore that it is important to separate air from the accumulator from places where oil can occur. Tests also revealed that the size of an external volume is not of any great importance when it comes to colleting oil. There was no significant difference in between of using a volume of 0.64 l or 0.19 l. However regarding overfilling it is favorable to have a larger volume since this increases the retarder’s capability to withstand oil leakage when it is overfilled.

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  • 9.
    Batmanian, Saro
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Naga, Pasam
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Control and balancing of a small vehicle with two wheels for autonomous driving2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Control and balancing of an inverted pendulum has gained a lot of attention over the past few decades due to its unstable properties. This has become a great challenge for control engineers to verify and test the control theory. To control and balance an inverted pendulum, proportional integrated derivative (PID) method or linear quadratic regulator (LQR) method can be used through which a lot of simulations can be done using the represented theories.Since urban population is increasing at a very alarming rate, there is a need to discover new ways of transportation to meet the future challenges and demands. Scania has come up with a new conceptual bus called NXT which aims to develop a modular vehicle that should configure and re-configure themselves between different transportation tasks. NXT vehicle has front and rear drive modules which can be represented as single axle, two-wheeled vehicles which in-turn can be viewed as an inverted pendulum with a huge Center of Gravity. Controlling and balancing of the pod or drive module precisely and accurately is an interesting challenge since it is an unstable inverted pendulum with huge center of gravity (COG). This behaviour of the system has created a research question whether the module is controllable or not.Therefore this thesis focuses on the possibility of controlling the pod which is a two-wheeled inverted pendulum vehicle with a COG offset. Also, the thesis focuses on the construction, mod-elling, testing and validation of a down-scaled model, what sensors are needed to balance the pod precisely, how the sensors must be integrated with the system and how the pod can be controlled remotely from a certain distance by a human. The developed pod houses the technologies like sensors, BLDC motor controllers, hoverboard, Arduino board and Bluetooth transmitters.The Master Thesis starts by presenting an introduction to the inverted pendulum theories, Scania NXT project, information about the research methods, thesis outline and structure . It continues by describing related literature about the inverted pendulums, segways, hoverboards, motor controllers and Arduino boards. Afterwards, the process of deriving a mathematical model, together with simulation in Matlab, Simulink and Simscape is described. Later, construction of the pod is made and lot of effort is put to run the pod. Since the pod needs to be controlled remotely by a human, a remote controlled systemis implemented via mobile phone using an app and finally the thesis is finished with a conclusion and ideas for future work.

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  • 10.
    Beltran Gutierrez, Javier
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Yujiao, Song
    Chalmers.
    Methods for Verification of Post-Impact Control including Driver Interaction2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis project focuses on the verification method of a safety function called PICthat stands for Post-Impact Control which controls the vehicle motion of passengercars after being exposed to external disturbances produced by a 1st impact, aiming atavoiding or mitigating secondary events.The main objective was to select a promising method, among several candidates, todevelop further for testing the function and the interaction with the driver. To do thisis was first necessary to map the real destabilized states of motion that are targeted bythe function. These states are referred as Post-Impact problem space and are acombination of variables that describes the host vehicles motion at the instant thedestabilizing force has ceased. Knowing which states are requested by the solutioncandidates, it is possible to grade the rig candidates based on the capability ofcovering the problem space. Then, simulating the proposed rig solutions withMatlab/Simulink models to investigate which candidate fulfils best the problem space.The result of the simulations and other criteria is that a moving base simulator(Simulator SIM4) is most fitted to research verification. The second mostadvantageous solution is the rig alternative called Built-in Actuators.

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  • 11.
    Berg, Mats
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Stensson Trigell, AnnikaKTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Selected and extended papers from the 21st symposium of the International Association of Vehicle System Dynamics: held at the Royal Institute of Technology (KTH), Stockholm, Sweden, August 17-21, 20092010Conference proceedings (editor) (Refereed)
  • 12.
    Berg, Mats
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Stensson Trigell, AnnikaKTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Special Issue: State of the Art Papers of the 21st IAVSD Symposium2009Conference proceedings (editor) (Refereed)
  • 13.
    Bhat, Sriharsha
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Industrial Engineering and Management (ITM), Centres, Integrated Transport Research Lab, ITRL.
    An Investigation into the Optimal Control Methods in Over-actuated Vehicles: With focus on energy loss in electric vehicles2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As vehicles become electrified and more intelligent in terms of sensing, actuation and processing; a number of interesting possibilities arise in controlling vehicle dynamics and driving behavior. Over-actuation with inwheel motors, all wheel steering and active camber is one such possibility, and can facilitate control combinations that push boundaries in energy consumption and safety. Optimal control can be used to investigate the best combinations of control inputs to an over-actuated system. In Part 1, a literature study is performed on the state of art in the field of optimal control, highlighting the strengths and weaknesses of different methods and their applicability to a vehicular system. Out of these methods, Dynamic Programming and Model Predictive Control are of particular interest. Prior work in overactuation, as well as control for reducing tire energy dissipation is studied, and utilized to frame the dynamics, constraints and objective of an optimal control problem. In Part 2, an optimal control problem representing the lateral dynamics of an over-actuated vehicle is formulated, and solved for different objectives using Dynamic Programming. Simulations are performed for standard driving maneuvers, performance parameters are defined, and a system design study is conducted. Objectives include minimizing tire cornering resistance (saving energy) and maintaining the reference vehicle trajectory (ensuring safety), and optimal combinations of input steering and camber angles are derived as a performance benchmark. Following this, Model Predictive Control is used to design an online controller that follows the optimal vehicle state, and studies are performed to assess the suitability of MPC to over-actuation. Simulation models are also expanded to include non-linear tires. Finally, vehicle implementation is considered on the KTH Research Concept Vehicle (RCV) and four vehicle-implementable control cases are presented.

    To conclude, this thesis project uses methods in optimal control to find candidate solutions to improve vehicle performance thanks to over-actuation. Extensive vehicle tests are needed for a clear indication of the energy saving achievable, but simulations show promising performance improvements for vehicles overactuated with all-wheel steering and active camber.

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  • 14.
    Bhat, Sriharsha
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Davari, Mohammad Mehdi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Nybacka, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Industrial Engineering and Management (ITM), Centres, Integrated Transport Research Lab, ITRL.
    Study on energy loss due to cornering resistance in over-actuated electric vehicles using optimal control2017In: SAE International Journal of Vehicle Dynamics, Stability, and NVH - V126-10, 2017Conference paper (Refereed)
    Abstract [en]

    As vehicles become electrified and more intelligent in terms of sensing, actuation and processing; a number of interesting possibilities arise in controlling vehicle dynamics and driving behavior. Over-actuation with in- wheel motors, all wheel steering and active camber is one such possibility, which facilitate the control strategies that push boundaries in energy consumption and safety. Optimal control can be used to investigate the best combinations of control inputs to an over-actuated system. This paper shows how an optimal control problem can be formulated and solved for an over-actuated vehicle case, and highlights the translation of this optimal solution to a real-world scenario, enabling intelligent means to improve vehicle efficiency. This paper gives an insight into the Dynamic Programming (DP) as an offline optimal control method that guarantees the global optimum. Therefore the optimal control allocation to minimize an objective function and simultaneously fulfill the defined constraints can be achieved. As a case study the effect of over-actuation on the cornering resistance were investigated in two different maneuvers i.e. step steer and sine with dwell, where in both cases the vehicle assumes to be in steady state situation. In this work the cornering resistance is the main objective function and maintaining the reference trajectory is the constraint which should be fulfilled. A parameter study is conducted on the benefits of over-actuation, and depending on the type of over-actuation about 15% and 50% reduction in cornering resistance were observed during step steer and sine with dwell maneuver respectively. From a second parameter study that focused on COG position from a safety perspective, it is more beneficial for the vehicle to be designed to under-steer than over-steer. Finally, a method is described to translate the offline optimal results to vehicle implementable controllers in the form of both feed-through lookup-tables and rule-based feed-forward control.

  • 15.
    Bhattacharyya, Shounak
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Sivaramakrishnan, Suraj
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Parameter Optimisation of EPAS Using CAE2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To keep up with technological as well as logistical challenges of the modern automobile market, major car manufacturing firms have resorted to virtual simulation tools. This enables the development as well as validation of vehicular models much before resources are invested into a new physical prototype.This project focuses on the development of a tool that would help in optimising the handling parameters of a vehicle. This is achieved by creating an optimization routine for tuning the various parameters of the Electronic Power Steering (EPAS). This process is usually done manually, by on-track testing, due to the difficulties in correlating Subjective Assessments (SA) with Objective Metrics (OM). Automating this process would help to reduce the overall research and development time, by providing a baseline tune for the EPAS parameters which could then be finely tweaked by manual track testing.The tool is built by interfacing various software in a multi-objective optimisation environment known as ModeFrontier. The modelling and simulations are performed in IPG CarMaker, with the post processing of the results taken care of by Sympathy for Data. Multiple optimization algorithms were tested to achieve the best optimisation routine. The EPAS parameters, namely the Basic Steering Torque, Active Return and Active Damping, act as the input to the optimization routine. The outputs of the model are the Objective Metrics, which provide a clear indication of the dynamic performance of a component. These metrics are optimized to _t the Steering DNA structure, which uniquely describes the attributes of a vehicle. The final optimised vehicle is manually tested at the track, to determine the real driving feel.

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  • 16.
    Blaszykowski, Sylvain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Design, modeling and implementation of the power train of an electric racing car: Control of a permanent magnet machine and implementation of a torque vectoring process in a FSAE car2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work emphasize the design, implementation and optimization of an electric power train for a Formula Student racing car.

    As a first part, theory and control of a PMSM machine, in an automotive context is investigated: a CAN bus communication system has been implemented and a field weakening strategy. Precise modeling of the car has then been performed using CarMaker, developed by IPG and making it possible to perform accurate tests and forecast regarding the performances of the vehicle. This model was then used to develop and test different launch control strategies together with a torque vectoring strategy and study the influence of different parameters on the vehicle performances.

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  • 17.
    Brondex, Julien
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Design of a prototype of an adaptive tire pressure system2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    At a time when the global warming stands out as one of the major concerns of this century, every effort to reduce the impact of human activity on the environment deserves to be considered seriously. The pollution generated by the road traffic has a large responsability in this phenomena. There are several ways to reduce the ecological footprint of road vehicles and one of those is to work on the so-called rolling resistance.

    The rolling resistance is largely influenced by the pressure in the tires. Keeping the optimal pressure in all four tires depending on the driving conditions is a guarantee of energy efficiency. Furthermore, tire pressure has also a significant impact on the wear of tires, the vehicle handling, the braking distance and the overall performances.

    In view of the foregoing, the company Yovinn AB, in collaboration with the Centre for ECO2 Vehicle Design, would like to design a prototype of an adaptive tire pressure system. Such a system would be able to automatically and continuously adapt the pressure in the tires to the driving situation in order to always maintain the optimal pressure. After a summary of what already exists in this field, the present work aims at describing a possible solution supported by calculations and CAD drawings. As it will be explained, the proposed solution enables a fast pressure adaptation in all four tires of a standard passenger car. Moreover, since it makes use of basic pneumatic components it is quite easy to implement for a relatively small cost. However, the system does not permit to make use of the energy stored in the air under pressure contained in the tires when deflation is required. The study was performed for one type of car only, i.e. the Volvo V70, and has to be adapted on a case-by-case basis.

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  • 18. Bucca, Giuseppe
    et al.
    Carnevale, Marco
    Collina, Andrea
    Facchinetti, Alan
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jönsson, Per-Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Adoption of different pantographs' preloads to improve multiple collection and speed up existing lines2012In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 50, no SUPPL. 1, p. 403-418Article in journal (Refereed)
    Abstract [en]

    The current collection using more than one pantograph is needed in railway operation to provide power to non-electrically connected traction units and, in some cases, to reduce current density on the collector strips that heavily influences the wear on the contacting bodies. The multiple current collection may become a critical condition due to the mechanical disturbances produced on the trailing pantographs by the interaction between the first pantograph and the catenary. The present-day evolution of pantograph preload regulating systems, exploiting pressure-controlled servo-valves driven by electronic units, allows a diversification of the preloads of front and rear pantographs. In this work, a suitable solution to improve multiple pantograph collection quality is analysed by the use of a lower mean force on the leading pantograph aimed at reducing the oscillations of contact wire the trailing pantograph is subjected to. This would improve the current collection quality of the trailing pantograph, and could be pursued even admitting a slight worsening of front pantograph's performances.

  • 19. Bucca, Guiseppe
    et al.
    Carnevale, Marco
    Collina, Andrea
    Facchinetti, Alan
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jönsson, Per-Anders
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Differentiation of pantographs’ preloads as a mean to improve multiple collection and speed upexisting lines2011In: Proceedings of 22nd Symposium of the International Association for Vehicle System Dynamics / [ed] Simon Iwnicki, 2011Conference paper (Refereed)
  • 20.
    Böhlander, Marcus
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Design and Safety Analysis ofEmergency Brake System forAutonomous Formula Car: In Reference to Functional Safety ISO 262622018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    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.

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  • 21. Bünte, T.
    et al.
    Andreasson, Johan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Global chassis control based on inverse vehicle dynamics models providing minimized utilisation of the tyre force potential2006In: VDI Berichte, ISSN 0083-5560, no 1931, p. 163-173Article in journal (Refereed)
  • 22.
    Casanueva, Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Altimira, Mireia
    KTH, School of Engineering Sciences (SCI), Mechanics. Mech. Eng. Dept., Tecnun (Univ. of Navarra).
    Course design oriented towards degree objectives in higher education2016In: EDULEARN16 Proceedings, IATED , 2016, p. 1662-1669Conference paper (Refereed)
    Abstract [en]

    The goal of engineering education is to facilitate the learning of technical knowledge and understanding, skills, and attitudes required by students to become successful engineers. In the Swedish higher education system, the qualifications for a master degree in engineering are listed in the Higher Education Ordinance. Such qualifications, also called Degree Objectives, have to be fulfilled on a programme level, that is, throughout all courses that form the programme. This requires a high level of communication and collaboration between all course responsibles and the programme coordinator. At the same time, it also restricts the freedom in the design of each individual course, as they all have fit into a 2-year-long educational puzzle. Designing courses from their conception with a view on fulfilling all the degree objectives would be more effective in terms of programme coordination. However, it poses new challenges, since it requires that all degree objectives related to skills and attitudes be fulfilled in each and every course through its learning activities. Is there a way of designing the course activities in such a way that most degree objectives are covered, while respecting the diversity in learning styles and maturity level of the students, and promoting self-regulation? We explore the possibilities of this course design concept when framed within the CDIO Initiative. We analyse the relative importance of the different Degree Objectives in Swedish Higher Education, and how these can be introduced in the Intended Learning Outcomes of each individual course while keeping in mind the personal evolution of the students at different stages of their education.

  • 23.
    Cauwet, Thomas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Development of waste heatrecovery systems for mobileheavy duty applications2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The focus of today’s automotive industry is to reduce emissions and fuel consumption of all vehicles.

    Concentrating on the truck industry, the last 20 years have focused largely on cutting emissions of particulate matter and nitrogen oxides. For the future, attention will be focused on fuel consumption and emissions of carbon dioxide. Waste heat recovery appears to be a very promising concept for fuel economy on long haul heavy duty Diesel trucks.

    After a general introduction on the concept of waste heat recovery and the Rankine cycle, this thesis work shows how to model and calibrate a cooling system circuit for a heavy duty Diesel engine equipped with a waste heat recovery system. Then an overview of the current transmission systems that are suitable to transfer energy from the waste heat recovery expander to the engine shaft is presented. For all transmission architectures, input speed range, speed ratio range, transmission efficiency as well as weight and size are detailed and compared to each other. Finally, these systems are modeled and integrated to a complete vehicle Simulink simulation platform and simulations are run on two highway driving cycles. Resulting average recovered powers and fuel consumptions are compared and the analysis finally shows that a gear train transmission has the best performance for this kind of driving cycle.

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  • 24.
    Cellière, Florian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Vehicle dynamic simulation and powertrain simulation of a heavy hybrid vehicle with interconnected suspensions2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis presents two simulations of a heavy hybrid vehicle, the first part of the thesis is focused on the specifications of the vehicle designed in accordance with the requirements based on the literature study of the soils where the vehicle will travel. The second part presents the study of the vehicle through two simulations. The first simulation is oriented on the dynamical behavior of the vehicle. The second simulation focuses on the energy management of the vehicle. The presented thesis is a multi-disciplinary study, combining knowledge on vehicle dynamics, hydraulic suspensions and hybrid systems.

    The dynamical simulation of the vehicle has been performed with Matlab/Simulink and the third party program Delft-Tire for the tire modelling. Specials features of Matlab have been used; SimMechanics for the modelling of the parts, links and joints of the vehicle, and SimHydraulics for the modelling of the hydraulic suspensions. The principal tests performed on the vehicle by the dynamical simulation are the tests defined by the NATO - STANAG standards as AVTP 03-170. The tests are a crossing obstacle test and different sine wave roads. The obstacle of the obstacle crossing test is an APG-10 obstacle, an 10 inch high step with vertical edges. The objective of this simulation is to verify the design of the suspension and to observe the forces created in each link of the suspension system in order to design the chassis and the suspension system. The sine wave driving tests are performed to highlight the influence of the different hydraulic connections. Finally the slalom test presents the influence of the hydraulic anti-roll bar.

    The results show that the vehicle suspension verifies the STANAG standard. The results show also that the forces applied at the wheel by the obstacle crossing defined in the AVTP 03- 170 are directly related to the diameter and the stiffness of the tire. The maximum forces encountered at the wheel corresponds to 2.5 G vertically and 1.5 G longitudinally. The sine wave driving and the slalom test are showing the benefits and the need for advanced hydraulic suspensions.

    The second simulation is the modelling of the hybrid power management of the vehicle. The simulation has been performed with the objectives to create a tool for sizing series hybrid powertrain. This simulation has also been performed with Matlab/Simulink and the Simscape Library.

    The tool created show that when, the vehicle is equipped with 150 kW of power generation and 300 kW of battery would be able to drive at a constant speed of 10 km/h with the terrain inputs evaluated from the literature study, but to create sufficient result the input parameters of the tools need to have a better definition.

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  • 25.
    Chahine, Richard
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Modeling of a World Rally Championship Car Damper and Experimental Testing of Its Components2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Rally cars are driven on many different types of surfaces. Each type of surface demands a special type of damper setup. In order to achieve optimum performance on the snow covered and icy Swedish roads, the gravel of the Spanish rallies and the smooth tarmac of the German rallies, a large flexibility in the possible damper settings is required. Prodrive, a British motorsport group, has been racing two Mini Countryman as factory team cars for BMW Mini as of Rally D’Italia in Sardinia in May 2011 and has requested that Öhlins Racing AB equips these cars with dampers. Öhlins Racing AB has been developing a damper for rally applications called the TPX. This damper is equipped with an Active Rebound Control system (ARC). The ARC allows for high levels of grip to be achieved together with good chassis control.

    The TPX damper with its ARC system is quite complex in structure. As there are many parts in the damper which can be altered, optimizing the damper would require a very large number of tests. A physical model of the TPX damper with its ARC system would reduce the time spent in the lab and help speed up the development of the damper. Prodrive would also like to a have a model of the damper that they can use in their model of the entire car which they use to setup the cars for races and to develop the car.

    The goal of this Master’s Thesis was therefore to create a model based in MatLab Simulink that qualitatively but not necessarily quantitatively replicated the dampers behavioral trends. Components which are very difficult to model, such as shim stacks, needed not be modeled. Their characteristics could be measured in the lab.

    During this Master’s Thesis project a model for the TPX damper was created using Simulink to model most of the physical parts of the damper. The rest of the model including its inputs and control were taken care of by a GUI. The model functions so simulations can be performed. Plotting the results of the simulations together with data from experimental tests was also made easy by the GUI. The results from comparisons between the simulated damper and the real object indicate that refinements need to be made to the model before it can be put to use as a tool for helping in optimizing the TPX damper’s construction. Hysteresis in the form of friction as well as damper flexibility does not seem to be negligible. The variation of the oil’s compressibility and the dynamic behavior of the check valves also need to be looked into. The graphs from the simulations seem to replicate the real dampers performance trends as intended. The numerical magnitudes of the data produced by the simulation are however not accurate. Overall the model produced during this master’s thesis seems to be a good step forward on the path to producing a useful model. Some suggestions for the next steps in improving the model are provided.

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  • 26.
    Chen, Siyao
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Robust motion estimation for vehicle dynamics applications using simplified models2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The overall aim of this thesis is to explore the accurate estimation methods for the vehicle motion with relatively cheap sensors. The vehicle states are essential to the vehicle control applications but sometimes expensive sensors are necessary to obtain accurate values. At first, a validation work for the rigid body motion estimation has been done and the results show that accurate linear and rotational accelerations can be achieved only with low-cost accelerome-ters. The main part of this work focuses on developing an estimator for the vehicle body angle, angle rate (including both roll and pitch) and the road an-gle, as a key block of the overall project Vehicle Dynamics Estimation. The estimation results are the inputs of another estimation block: vehicle lateral dynamic estimator; and part of the important inputs of the angle estimator (velocities and the time derivative) also come from the lateral dynamic esti-mator instead of the expensive sensors. The estimation technique employed in this work is the linear augmented Kalman filter with the unknown road angles as the augmented estimation states. The roll and pitch motion are assumed to be decoupled with each other, and the linear mass-damper-spring dynamic model is adopted to obtain the equations of the vehicle states. Some unknown parameters shown in the dynamic equations are identified at first with SimRod testing data and the results are satisfactory. The road angles are modeled as a zero-order random walk model. The bicycle model, vehicle body-road and ve-hicle body-frame kinematics are used to derive the measurement equations of the Kalman filter. After the simulation and measurement inputs are obtained, the process and measurement error covariance are tuned to finally decide the estimation results. Also, SimRod testing data are used to validate the results, and the estimation performance for the vehicle body angle and angle rate are good; while the road angles need to be further validated with more available data set.

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  • 27.
    Chevatco, Vladimir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Exploration of steering feel2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis, the concept of steering feel, as experienced by the driver, is explored. First a literature review is conducted to highlight previous work on this topic. From this review, the Norman on-centre test and steering wheel torque are identified as important concepts, and are chosen to form the base of this thesis. Following this, steering system and tyre construction are described, and a single-track mathematical model of a car and its tyres is illustrated. Those models are then implemented in Simulink and are used to simulate the Norman on-centre test and explore the effects of vehicle mass, steering ratio and power-steering servo curves on steering wheel torque. Without power steering, vehicle mass and steering ratio are identified as having the largest effect on the steering torque. With power steering added to the model, it becomes the dominating factor in shaping the steering wheel torque, and it is concluded that future research in this area is likely to focus on power-steering and steer-by-wire effects.

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  • 28.
    Christ, Florian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Adaption and evaluation of transversal leaf spring suspension design for a lightweight vehicle using Adams/Car2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This investigation deals with the suspension of a lightweight medium-class vehicle for four passengers with a curb weight of 1000 kg. The suspension layout consists of a transversal leaf spring and is supported by an active air spring which is included in the damper. The lower control arms are replaced by the leaf spring ends. Active ride height control is introduced to compensate for different vehicle load states. Active steering is applied using electric linear actuators with steer-by wire design. Besides intense use of light material the inquiry should investigate whether elimination of suspension parts or a lighter component is concordant with the stability demands of the vehicle. The investigation is based on simulations obtained with MSC Software ADAMS/Car and Matlab. The suspension is modeled in Adams/Car and has to proof it's compliance in normal driving conditions and under extreme forces. Evaluation criteria are suspension kinematics and compliance such as camber, caster and toe change during wheel travel in different load states. Also the leaf spring deflection, anti-dive and anti-squat measures and brake force distribution are investigated. Based on a simplified version of the leaf spring suspension design a full vehicle model is created. The comparison between the suspension models evaluates the same basic suspension parameters to ensure the compliance. Additionally roll rate and understeer gradient are investigated. It can be shown that the vehicle equipped with transversal leaf spring instead of lower control arms fulfils the set kinematics and compliance requirements. Road holding performance is assured for normal driving conditions on public roads.

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  • 29.
    Cocron, Peter
    et al.
    TU Chemnitz.
    Neumann, Isabel
    TU Chemnitz.
    Kreußlein, Maria
    TU Chemnitz.
    Pereira Cocron, Maria
    TU Chemnitz.
    Wanner, Daniel
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Bierbach, Maxim
    Federal Highway Research Institute (BAST).
    Augusto, Bruno
    VTI.
    Driver and vehicle behaviour to power train failures in electric vehicles – experimental results of field and simulator studies.2014Report (Refereed)
    Abstract [en]

    see fulltext

  • 30.
    Conte, Francesco
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Expanding the brush tire model for energy studies2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Considering the more and more important issues concerning the climate changes and the global warming, the automotive industry is paying more and more attention to vehicle concepts with full electric or partly electric propulsion systems. The introduction of electric power sources allow the designers to implement more

    advanced motion control systems in vehicle, such as active suspensions. An example of this concept is the Autonomous corner module (ACM), designed by S. Zetterström. The ACM is a modular based suspension system that includes all features of wheel control, such as control of steering, wheel torque and camber

    individually, using electric actuators. With a good control strategy it is believed that is it possible to reduce the fuel consumption and/or increase the handling properties of the vehicle.

    In particular, camber angle has a significant effect on vehicle handling. However, very few efforts have been done in order to analyse its effects on tire dissipated energy.

    The aim of this study is to develop a new tire model, having as starting point the simple Brush Tire model, in order to analyse the tire behaviour, in terms of forces generated and energy dissipated, for different dynamic situations. In order to reach this scope, the characteristic equations of the rubber material are implemented

    in a 3D Multi-Line brush tire model. In this way the energy dissipated, thus the rolling resistance force, can be studied and analysed, considering also the tire geometry.

    From the results of this work it is possible to assert that the angular parameters (e.g. camber angle) affect the power losses in rolling tires, as well as the tire geometry influences their rolling resistance. Thus, using a good control strategy, it is possible to reduce the power losses in tires.

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  • 31.
    Dabhi, Meet
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Vaidyanathan, Karthik Ramanan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Automation and synchronizationof traction assistance devices toimprove traction and steerability ofa construction truck2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Automotive development has always been need-based and the product of today is an evolutionover several decades and a diversied technology application to deliver better products to theend users. Steady increase in the deployment of on-board electronics and software is characterizedby the demand and stringent regulations. Today, almost every function on-board a modernvehicle is either monitored or controlled electronically.One such specic demand for AB Volvo arose out of construction trucks in the US market. Usersseldom have/had a view of the operational boundaries of the drivetrain components, resultingin inappropriate use causing damage, poor traction and steering performance. Also, AB Volvo'sstand-alone traction assistance functions were not suciently capable to handle the vehicle useconditions. Hence, the goal was set to automate and synchronize the traction assistance devicesand software functions to improve the traction and steerability under a variety of road conditions.The rst steps in this thesis involved understanding the drivetrain components from design andoperational boundary perspective. The function descriptions of the various traction softwarefunctions were reviewed and a development/integration plan drafted. A literature survey wascarried out seeking potential improvement in traction from dierential locking and also its eectson steerability. A benchmarking exercise was carried out to identify competitor and suppliertechnologies available for the traction device automation task.The focus was then shifted to developing and validating the traction controller in a simulationenvironment. Importance was given to modeling of drivetrain components and renement ofvehicle behavior to study and understand the eects of dierential locking and develop a differentiallock control strategy. The modeling also included creating dierent road segments toreplicate use environment and simulating vehicle performance in the same, to reduce test timeand costs. With well-correlated vehicle performance results, a dierential lock control strategywas developed and simulated to observe traction improvement. It was then implemented onan all-wheel drive construction truck using dSPACE Autobox to test, validate and rene thecontroller.Periodic test sessions carried out at Hallered proving ground, Sweden were important to re-ne the control strategy. Feedback from test drivers and inputs from cross-functional teamswere essential to develop a robust controller and the same was tested for vehicle suitability andrepeatability of results. When comparing with the existing traction software functions, the integrateddierential lock and transfer case lock controller showed signicantly better performanceunder most test conditions. Repeatable results proved the reliability of developed controller.The correlation between vehicle test scenarios and simulation environment results indicated theaccuracy of software models and control strategy, bi-directionally.Finally, the new traction assistance device controller function was demonstrated within ABVolvo to showcase the traction improvement and uncompromising steerability.

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  • 32.
    Dahlberg, Carl
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Reducing Bodybuilder Waste on SCANIA Trucks2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In a world of fierce competition that is the reality for heavy truck manufacturers, it is important to optimize every step of production to the greatest extent. The Swedish truck manufacturer SCANIA early adopted such ideas and has put great efforts to implement a concept called lean production. As a part of the company’s strive for continuous improvement, all parts of the value adding chain shall be as efficient as possible.  Previously this work has been focused inside the SCANIA organization but as demands on production volume and profit margin increases, focus turns outside the factory premises. A bodywork is fitted as a last step in the completion of many trucks. This is done by external companies called bodybuilders, outside the control of the factory. In this thesis, the bodybuilder induced waste is addressed from a global perspective.

    The report is entirely based on interviews with people inside SCANIA, SCANIA’s Swedish business unit, bodybuilders in both Sweden and Poland and a Swedish employer’s organization. Through these interviews, the difficulties surrounding the subject have been mapped from different perspectives. As a complement to the interviews, a program that calculates the annual waste related to shortened chassis frames has been developed.

    The main waste inducing problem areas found in this thesis is:

    -        Poor communication between seller and bodybuilder before specifying and ordering the chassis.

    -        Poor communication between factory and bodybuilder regarding existing chassis preparations.

    -        A high degree of customer involvement in the bodybuilder process on the Swedish market.

    -        High price sensitivity on the Polish market makes chassis specified without preparations more attractive.

    -        Highly diverse customer demands on the Swedish market.

    -        Insufficient ordering tools to meet the customer demands of individually customized vehicles.

    -        Discrepancies between the global focus at factory and the local nature of the market on which the sellers exist.

    The costs related to shortened chassis frames alone is estimated to cost SCANIA 5 000 000 SEK annually in terms of reduced chassis frame waste and decreased costs for bound investments when chassis are standing at bodybuilders. In order to go from today’s annual production of 70 000 vehicles to the long-term goal of 150 000 vehicles/year, it will be crucial to reduce waste throughout the whole production chain. This will require better prepared vehicles from factory, better ordering software for the sellers and less rigid customer behaviour on certain markets. The increased communication between seller, bodybuilder and factory will be necessary and could be implemented through cooperation between selected bodybuilders and sellers in a preferred program.

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  • 33. Dahlberg, E.
    et al.
    Stensson, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    The dynamic rollover threshold - a heavy truck sensitivity study2006In: International Journal of Vehicle Design, ISSN 0143-3369, E-ISSN 1741-5314, Vol. 40, no 03-jan, p. 228-250Article in journal (Refereed)
    Abstract [en]

    Knowledge of rollover mechanics, which is required in heavy truck development, commonly relies on a static analysis, providing the steady-state rollover threshold, SSRT. In a rolling vehicle, kinetic energy is always present and that deteriorates the analysis of roll stability from SSRT and implies the need for a dynamic rollover threshold, DRT as a complement. A method to determine DRT is presented and a parameter sensitivity study The influences on SSRT and DRT, including interaction effects, from roll stiffnesses and roll centre heights, are calculated. Results show that a rigid truck and a tractor semitrailer combination are unequally sensitive to parameter changes. Design changes can hence affect SSRT and DRT differently, which indicates that two vehicles can be equally stable statically but differently dynamically. Therefore, if DRT is not analysed, a redesign of a vehicle can deteriorate roll stability even though it appears to improve it.

  • 34.
    Daniel, Ajay
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Suspension design for Uniti, a lightweight urban electric vehicle2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Climate change is real and the automotive industry is no longer in denial that electrification of vehicles is the future. But what if there is a better solution to meeting the commuting requirements in an urban environment than a form of a car that we are so familiar with? Something which gives the freedom of mobility like a car but is more practical. Perhaps a Uniti? Uniti aims at providing a smart solution to urban commute, something which is sustainable, fun and in step with the strides made in technology. This involved starting from a clean slate and attacking the very fundamental problem; a two-ton machine meant for carrying four to five people being used by only one person for majority of its lifespan, which makes all the more less sense in an urban environment. Hence came into life Uniti; a lightweight electric vehicle in the L7e category designed to be the second family car. Designing such a vehicle from the standpoint of vehicle dynamics is tricky as the user shapes the mass of the vehicle significantly. The driver and passenger in this vehicle accounts for almost a quarter of the total weight. That along with the high unsprung mass coming with the use of in wheel electric motors makes this project all the more challenging. The thesis is aimed at providing a starting point to build on to a robust suspension design. The fundamentals of vehicle dynamics were used to build up mathematical models in MATLAB and simulations were done with ADAMS/Car to study and optimize the design. All said and done the scope of the work was limited considering it had to be built from scratch but the models developed and the concepts laid out would hopefully be a good foundation to develop it into the prefect one.

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  • 35.
    Daniel, Wanner
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Nybacka, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Experimental implementation of a fault handling strategy for electric vehicles with individual-wheel drives2016In: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015, CRC Press, 2016, p. 147-152Conference paper (Refereed)
    Abstract [en]

    This paper presents a fault handling strategy for electric vehicles with four individual-wheel drives, which are based on wheel hub motors. The control strategy to handle the faults is based on the principle of control allocation and is implemented in an experimental vehicle. Experimental tests has been performed with the experimental vehicle and with simulation. The results show that the directional stability of such a vehicle can be improved for the analysed manoeuvre and failure mode, and the tendencies of the experimental results correspond with the simulation results. It has been found that the lateral and yaw motion could be strongly improved. 

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    IAVSD_11:2.pdf
  • 36.
    Dankowicz, H.
    et al.
    Virginia Polytechnic Institute and State University, Department of Engineering Science and Mechanics, Virginia, USA.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Control of near-grazing dynamics in impact oscillators2005In: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 461, no 2063, p. 3365-3380Article in journal (Refereed)
    Abstract [en]

    A method is presented for controlling the persistence of a local attractor near a grazing periodic trajectory in a piecewise smooth dynamical system in the presence of discontinuous jumps in the state associated with intersections with system discontiunities. In particular, it is shown that a discrete, linear feedback strategy may be employed to retain the existence of an attractor near the grazing trajectory, such that the deviation of the attractor from the grazing trajectory goes to zero as the system parameters approach those corresponding to grazing contact. The implementation relies on a local analysis of the near-grazing dynamics using the concept of discontinuity mappings. Numerical results are presented for a linear and a nonlinear oscillator.

  • 37. Dankowicz, H.
    et al.
    Svahn, Fredrik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Control of instabilities induced by low-velocity collisions in a vibro-impacting system with friction2009In: Vibro-Impact Dynamics of Ocean Systems and Related Problems, 2009, p. 41-52Conference paper (Refereed)
    Abstract [en]

    The onset of low-velocity collisions in vibro-impacting systems induces instabilities in the system dynamics that, when not checked, may result in sudden, and unanticipated discontinuous transitions between distinct steady-state responses. This paper illustrates this phenomenology in an example system that includes dry friction. Here, the instability is associated with the zero-velocity contact of an oscillatory unilateral constraint and a stationary mass suspended through a preloaded spring. The analysis summarizes observations on the passive response of the mass under variations in the oscillation amplitude of the constraint. A control strategy is subsequently shown to successfully suppress the instability. The paper concludes with suggestions for applications of this phenomenology as well as a description of similar observation in mechanical systems with or without friction and with rigid as well as compliant contact.

  • 38.
    Dankowicz, Harry
    et al.
    Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign.
    Svahn, Fredrik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    On the stabilizability of near-grazing dynamics in impact oscillators2007In: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 17, no 15, p. 1405-1429Article in journal (Refereed)
    Abstract [en]

    A constructive proof is presented for the existence of event-driven control strategies that guarantee the local persistence of system attractors with at most low-velocity contact in vibro-impacting oscillators. In particular, sufficient conditions are formulated on the linearization of the control strategies along a grazing periodic trajectory, i.e. an oscillating motion that achieves zero-relative-velocity contact with a mechanical obstacle, to ensure the asymptotic stability of the grazing trajectory and, consequently, sustained dynamics in the vicinity of the grazing trajectory even under small changes in system parameters. The implications of the methodology are illustrated with linear and nonlinear, single- and multiple-degree-of-freedom examples of vibro-impact oscillators.

  • 39.
    Davari, Mohammad Mehdi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    A tyre model for energy studies in vehicle dynamics simulations2015Licentiate thesis, comprehensive summary (Other academic)
  • 40.
    Davari, Mohammad Mehdi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Exploiting over-actuation to reduce tyre energy losses in vehicle manoeuvres2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to environmental and economic challenges road vehicles need bettersolutions to reduce energy consumption. Improvement in tyre rolling e-ciency is one of the key enablers for lower energy consumption. The shifttowards electrication and intelligent driving creates new opportunities todevelop energy-ecient vehicles. For instant over-actuated vehicles whichenables dierent objectives such as safety, performance and energy e-ciency to be fullled during a manoeuvre. The objective of this thesis is todevelop a simulation environment to simulate the energy dissipated fromthe tyre in order to investigate the potential to controlling dierent chassisparameters to reduce rolling losses during driving.The rst part of the thesis is dedicated to develop a high-delity semi-physical non-linear tyre model called the Extended Brush Tyre Model(EBM) to be used for energy studies in vehicle dynamics simulations andlater answer whether it is reasonable to believe that there is any potentialto reduce the rolling loss, and thereby energy consumption, using over-actuation.In the second part of the thesis the benets of over-actuation are invest-igated to enable rolling loss reduction. A control strategy using camber-sideslip control (CSC) is proposed. The allocation problem is solved in the formof an optimisation problem using Dynamics Programming (DP) and ModelPredictive Control (MPC). Exploiting the function for a chosen vehicle ina simulation environment shows a signicant improvement of about 60% inrolling loss reduction while maintaining path tracking. Also by using thisfunction the tyre forces can be distributed more evenly while maintainingthe global force, which results in an increase in the available tyre forcesthat is especially benecial when driving at the limit. It is revealed thatoptimising the vehicle manoeuvre from an energy perspective is sometimesin con ict with the safety demand, thus the energy and safety criteria needto be considered simultaneously during optimisation.Finally, experimental studies using an over-actuated concept vehicleconrmed that the CSC function can reduce overall energy consumptionduring low velocity manoeuvres up to about 13%. By increasing the speed,the saving potential decreases but the contribution is nonetheless of signi-cance. The developed simulation environment, including the EBM, willenable future studies of dierent solutions using over-actuation to reducerolling losses in dierent types of vehicles and driving tasks.

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  • 41.
    Davari, Mohammad Mehdi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Energy Efficiency Analyses of a Vehicle in Modal and Transient Driving Cycles including Longitudinal and Vertical Dynamics2017In: Transportation Research Part D: Transport and Environment, ISSN 1361-9209, E-ISSN 1879-2340, Vol. 53, p. 263-275Article in journal (Refereed)
    Abstract [en]

    The growing concerns about the environmental issues caused by vehicles and a strive forbetter fuel economy, urge the legislators to introduce conservative regulations on vehicletesting and homologation procedures. To have accurate evaluations, driving cycles thatcan sufficiently describe the vehicles’ conditions experienced during driving is a prerequisite.In current driving cycles there are still some issues which are disregarded. The aim ofthe presented work is to study the contribution of chassis and vehicle dynamics settings ontyre rolling loss in comparison with the original assumptions made in the NEDC, FTP andHWFET driving cycles. A half-car model including a semi-physical explicit tyre model tosimulate the rolling loss is proposed. For the chosen vehicle and tyre characteristics,depending on the specific chassis settings and considered driving cycle, considerable differenceup to 7% was observed between the energy consumption of the proposed- and conventionalapproach. The current work aims to provide the legislators with a betterinsight into the real effects of chassis and vehicle dynamics during the certification processto further improve the test related procedures required for homologation such as generationof road load curves. I.e., the aim is not to provide a new homologation process, sincethere are also other effects such as road roughness and tyre temperature that need to beconsidered. The results are also of interest for the vehicle manufacturers for further considerationsduring test preparation as well as in the development phase in order to reduce theenvironmental impacts.

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  • 42.
    Davari, Mohammad Mehdi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    A Multi-Line Brush Based Tyre Model to Study the Rolling Resistance and Energy Loss2015In: Proceedings of 4th International Tyre Colloquium: Tyre Models for Vehicle Dynamics Analysis, Guildford, UK (2015), 2015Conference paper (Refereed)
    Abstract [en]

    This study aim to develop a three dimensional multi-line brush based tyre model for investigating the rolling resistance and energy loss in tyres. The losses in the model are characterised by the external losses originated from the sliding phenomenon in the tyre contact patch, and the internal losses due to the tyre viscoelastic nature which is employed by a rubber model. The Extended Brush tyre Model (EBM) proposed in this work can be used to estimate the dissipated energy and the rolling resistance under different driving manoeuvres and wheel conditions. This paper focuses on the estimation of energy loss and in-plane rolling resistance.

  • 43.
    Davari, Mohammad Mehdi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Edrén, Johannes
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Investigating the Potential of Wheel Corner Modules in Reducing Rolling Resistance of Tyres2014In: Proceedings of FISITA "14 World Automotive Congress, Maastricht, Netherlands (2014), 2014Conference paper (Refereed)
    Abstract [en]

    The improvement in tire rolling efficiency is one of the key elements to optimize the fuel economy and thereby reduce the vehicle emissions. Earlier efforts to reduce the rolling resistance have mainly been focusing on new materials in the tire compounds. The overall research aim of this study is to present the potentials ofimplementing innovative chassis concepts with the focus on Wheel Corner Modules (WCM) by describing thepossibilities in affecting rolling resistance and relating them to previous research findings. The core idea of theconcept is to actively control and actuate all degrees of freedom in the wheel i.e. implementing steering,suspension and propulsion functions into a unique module which can be implemented in each corner of the vehicle. Using this concept the limitations of traditional wheel kinematics can be resolved extensively. This article presents the first step towards creating a vehicle simulation model that can show how the WCM functionality can influence the rolling resistance. A model of loss is chosen after analysing the behaviour of three different rubber models and then implemented into a brush tire model. An effective way, but less complicatedcompared to current methods, to introduce the loss into tire model is presented. In conventional suspensions, thedesign is compromising between for example safety, comfort and rolling resistance, etc. at all drivingconditions. However, using the WCM, the possibility of achieving a better compromise between those objectivesis possible. Finally, based on WCM functionalities a plausible control architecture is proposed.

  • 44.
    Davari, Mohammad Mehdi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jonasson, Mats
    KTH.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Rolling Loss Optimisation of an Over-actuated Vehicle using Predictive Control of Steering and Camber ActuatorsArticle in journal (Refereed)
  • 45.
    Davari, Mohammad Mehdi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jonasson, Mats
    KTH.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    An Energy Oriented Control Allocation Strategy for Over-actuated Road VehiclesArticle in journal (Refereed)
  • 46.
    Davari, Mohammad Mehdi
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jonasson, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Rolling loss analysis of combined camber and slip angle control2016Conference paper (Refereed)
    Abstract [en]

    The objective of this work is to present a new functionality of over-actuated systems, such as Wheel Corner Modules, to reduce the rolling loss in vehicles. The findings are based on numerical simulations using a bicycle model coupled with a newly proposed tyre model which is capable of simulating the tyre losses during vehicle motions. The results show that for the considered vehicle in the considered manoeuvre the rolling loss can be reduced about 25–40% by proper control of camber and slip angle combinations, while still maintaining the vehicle performance.

  • 47.
    De la Gardie, Fredrik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Road unevenness relation to road safety - a vehicle dynamics study2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this Master thesis in Vehicle Engineering, is to study the road unevenness relation to road safety. The long term objective is to be able to prioritize which road section that is in the need of repair and maintenance prior to other road sections.

    This study focus on how close to an acceptable safety limit the vehicle is handled when it is run over different road surfaces. This applies to straight road sections as well as cornering, where the road surface is uneven and bumps/pits occurs. No driver behaviour or random actions are analysed but these aspects will be included in the overall discussion.

    The method to analyse this is through computer simulation. From a Volvo S40 a computerised vehicle model has been developed in Matlab and the effect of different road unevenness has been implemented and analysed. Forces that are generated by the unevenness of the road are compared with the normal forces that a driver needs to correct the course based on the friction between tire and road surface. On this basis, a margin to the risk of losing the grip can be estimated. In this way it can be interpreted how a road section contributes more or less, compared to another section, to whether the vehicle is closer to a safe limit from a vehicle dynamic perspective.

    The vehicle model has been analysed at a speed of 70 km/h with the simplification that the irregularities can be described by sinusoidal shapes. For larger bumps or dips in the road the results show that both front and rear tires can absorb side forces so that stability can be achieved. If the grip would deteriorate due to gravel, ice, etc. there is a risk that the vehicle loses steering control and/or cord leading to damage of the tyre and consequently an accident will occur. For the analysed road unevenness in the form of bumps and pits the tires do not have any ability to absorb required side forces during an avoidance manoeuvre when travelling over the road due to the tyre model used.

    It is therefore important that a section with varying unevenness are analysed to determine a maximum speed so that the control of the vehicle during the whole distance can be maintained regardless of whether control needs to be done in connection with the unevenness.

    A recommendation of future work in this area is to develop this model to make it more robust and to update the input data with relevant data for one today representative car and to carry out a more detailed full-scale modelling with also lateral simulations. If the model was verified with measured normal forces for a test car that has travelled over various bumps and pits, this would also be valuable to confirm the validity of the model. There would also be improvements if available road profile is implemented in the analysis so that realistic examples can be analysed for better real-world analysis.

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  • 48.
    Dhanabalan, Yogeshwar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Numerical study of a wind tunnel setup for measuring train slipstream with Detached Eddy Simulation2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    High speed trains have become an integral part of the transportation systems around the world. With increasing speed, very high velocities are generated in the region around the train known as slipstream. Experimental studies have been conducted over the last few decades to study the effect of these phenomena. Slipstream velocities have been measured using anemometers placed near real trains running on the tracks and model trains running on rigs like moving model rig and rotating rail rig. However, most of these studies are quite expensive to conduct. The purpose of this thesis is to find an alternative way to measure the slipstream. Detached Eddy Simulation is used to simulate the flow around a 1:15 scaled model of an ETR500 high speed train with different configurations similar to tests conducted on the track and in the wind tunnel. The results from the simulations are compared with the data obtained from experimental tests conducted on the Torino-Novara high speed line. A wind tunnel test is also carried out to validate the CFD data. It is concluded from the results that the wind tunnel setup with a slip floor in front of the train can be used to find out if the train produces slipstream velocities that are within the limits indicated by the TSI standards.

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  • 49.
    Didner, Olof
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Ingvarsson, Gustaf
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Framtida förändringar i konstruktionen hos fordon som en följd av autonoma system2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This is a Bachelor thesis about self-driving cars and their design in the future. Conclusions about the future design are drawn by analyzing today’s cars and their driver assistant systems, along with analyses of developing systems and prototype cars that companies develop.

    To do this, certain demands on self-driving cars were listed. They concern among others maneuverability, oversight around the car, pedestrians, different weather conditions and cyber security. The developing systems examined were highway pilot, platooning and Safe Intelligent Mobility. The prototype cars studied were Google’s self-driving car and Mercedes F 015 Luxury in Motion.

    With the implementation of the existing systems, no main changes in design have been made. Looking forward, vehicles could get a rounder shape, lack side mirrors and have an interior designed for other purposes than driving. Sensors could also be moved to more protected positions, which might lead to a different design.

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  • 50.
    Drugge, Lars
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Juhlin, Magnus
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Aerodynamic loads on buses due to crosswind gusts: extended analysis2010In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 48, p. 287-297Article in journal (Refereed)
    Abstract [en]

    The objective of this work is to use inverse simulations on measured vehicle data in order to estimate the aerodynamic loads on a bus when exposed to crosswind situations. Tyre forces, driver input, wind velocity and vehicle response were measured on a typical coach when subjected to natural crosswind gusts. Based on these measurements and a detailed MBS vehicle model, the aerodynamic loads were estimated through inverse simulations. In order to estimate the lift force, roll and pitch moments in addition to the lateral force and yaw moment, the simulation model was extended by also incorporating the estimation of the vertical road disturbances. The proposed method enables the estimation of aerodynamic loads due to crosswind gusts without using a full scale wind tunnel adapted for crosswind excitation.

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