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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.

  • 3.
    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. 

  • 4.
    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.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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)
  • 9.
    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)
  • 10.
    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.

  • 11.
    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.

  • 12.
    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.

  • 13.
    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.

  • 14. 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.

  • 15. 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)
  • 16. 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)
  • 17.
    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.

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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.

  • 22.
    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.

  • 23.
    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

  • 24.
    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.

  • 25.
    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.

  • 26.
    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.

  • 27. 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.

  • 28.
    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.

  • 29.
    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. 

  • 30.
    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.

  • 31. 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.

  • 32.
    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.

  • 33.
    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)
  • 34.
    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.

  • 35.
    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.

    The full text will be freely available from 2019-04-01 23:39
  • 36.
    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.

  • 37.
    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.

  • 38.
    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)
  • 39.
    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)
  • 40.
    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.

  • 41.
    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.

  • 42.
    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.

  • 43.
    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.

  • 44.
    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.

  • 45.
    Drugge, Lars
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Larsson, Tobias
    Luleå University of Technology.
    Stensson, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Modelling and simulation of catenary-pantograph interaction2000In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 33, p. 202-213Article in journal (Refereed)
  • 46.
    Drugge, Lars
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Lennartsson, Anders
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    A laboratory model study of a railway current collection system2008In: Proceedings of the ASME Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Vol 5, PTS A-C,, NEW YORK: AMER SOC MECHANICAL ENGINEERS , 2008, p. 1805-1810Conference paper (Refereed)
    Abstract [en]

    A vital system on modem high-speed electric trains is the overhead catenary system and the pantograph current collector. As speed limits are increased, train operators and railway engineers need measures of system performance in a number of situations. In this work a laboratory model is built to study the pantograph behaviour on curved track running on a catenary system with large stiffness variation. The model is designed to be simple, yet exhibit the most characteristic dynamic properties of the real system. Another objective is the possibility to run the pantograph at speeds near the wave propagation velocity of the contact wire. The situation of several trailing pantographs, with even spacing, which excites the system to steady state, is considered. Effects of changes in design features such as tension in the contact wire and torsion and translation stiffness of components in the pantograph are studied for different speeds. The interaction is complex and the performance depends on the dynamic properties of both the catenary system and the pantograph. The results show that the pantograph configuration mainly affects the size of amplitudes in the system while the contact wire tension influences at which velocities large amplitudes and contact losses occur.

  • 47.
    Edrén, Johannes
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Exploring force allocation control of over actuated vehicles2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    As the concern for environmental changes and diminishing oil resources grows more and more, the trend of new vehicle concepts now includes full electric or partly electric propulsion systems. The introduction of electric power sources enables more advanced motion control systems due to electrification of the vehicle's actuators, such as individual wheel steering and in wheel hub motors. This can enable a control methodology that uses different chassis control strategies into a system that will be able to fully utilise the vehicle. Due to this, future vehicles can be more optimised with respect to energy consumption, performance and active safety.

    Force allocation control is a method that distributes the wheel forces to produce the desired response of the vehicle. In order to evaluate if this methodology can be implemented in future series production vehicles, the aim of this work is to explore how force allocation control can be utilised in a real vehicle to improve vehicle dynamics and safety.

    In order to evaluate different approaches for generic vehicle motion control by optimization, modelling and simulation in combination with real vehicle experiments will be needed to fully understand the more complex system, especially when actuator dynamics and limitations are considered. The use of a scale prototype vehicle represents a compromise between development cost, efficiency and accuracy, as it allows realistic experiments without the cost and complexity of full vehicle test. Moreover since the vehicle is unmanned it allows studies of at-the-limit situations, without the safety risks in full vehicle experiments.

    A small scale prototype vehicle (Hjulia) has been built and equipped with autonomous corner module functionality that enables individual control of all wheels. A cost effective force allocation control approach has been implemented and evaluated on the prototype vehicle, as well as in vehicle simulation. Results show improvement of stopping distance and vehicle stability of a vehicle during split-m braking. The aspects of vehicle dynamic scaling are also discussed and evaluated, as it is important to know how the control implementation of small scale prototype vehicles compares with full size vehicles. It is shown that there is good comparison between vehicles of different scales, if the vertical gravitational acceleration is adjusted for. In Hjulia, gravity compensation is solved by adding a specific lifting rig.

    Studies of vehicles considering optimal path tracking and available actuators are also made to evaluate control solutions of evasive manoeuvres at low and high friction surfaces. Results show differences in how the forces are distributed among the wheels, even though the resulting global forces on the vehicle are approximated to be scaled by friction. Also it is shown that actuator limitations are critical in at-the-limit situations, such as an obstacle avoidance manoeuvre. As a consequence these results will provide good insights to what type of control approach to choose to handle a safety critical situation, depending on available actuators.

    The built prototype vehicle with implemented force allocation control has shown to be a useful tool to investigate the potential of control approaches, and it will be used for future research in exploring the benefits of force allocation control.

  • 48.
    Edrén, Johannes
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Motion modelling and control strategies of over-actuated vehicles2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the growing concern for environmental change and uncertain oil resources, the development of new vehicle concepts will in many cases include full or partial electric propulsion. The introduction of more advanced powertrains enables vehicles that can be controlled with a variety of electric actuators, such as wheel hub motors and individual steering. With these actuators, the chassis can be enabled to adjust its properties depending on the driving situation.

    Manoeuvring of the vehicle, using for example electric propulsion, braking, suspension, steering and camber control may also allow a variety of combinations which, if properly utilised, can increase the outer limits of vehicle performance and safety. The fact that the vehicle has a greater number of actuators than required to control a certain number of degrees of freedom is called over-actuation. Since there is a great need for energy optimised vehicles, energy efficient control is also required. For this reason, this work is about the allocation of wheel forces can improve safety, performance and energy efficiency in future electrified vehicles in different driving situations.

    Studies of optimally controlled vehicles show that performance, safety and efficiency can be improved by utilising available actuators in over-actuated vehicles. Path tracking and optimal actuator control signals are evaluated in evasive manoeuvres at low and high friction surfaces. The results show how the forces are distributed differently among the wheels, even though the resulting global forces on the vehicle are similar. Optimal control of camber angles and active suspension show that vehicle performance and safety can be greatly improved. The limits of tyre forces can be increased and better utilised in a way that a passive system is unable to achieve. Actuator performance is also shown to be important, however even low actuator performance is shown to be sufficient to improve vehicle performance considerably. Energy efficiency is also improved as unnecessary vehicle motions are minimised during normal driving and wheel forces are used in a better way.

    Simplified algorithms to control available actuators, such as wheel angles, vertical actuation and propulsion torques, have been developed, based on the analysis of the results of the optimisation studies. Analyses of the impact of these simplifications have been made. For the cases studied, it has been shown that it is possible to get significantly better performance at reasonable levels of actuator performance and control complexity. This helps to simplify the introduction of this technology in electrified vehicles.

    Control allocation is a method that distributes the wheel forces to produce the desired response of the vehicle. Simplified control allocation algorithms are proposed that allocate wheel forces in a way that resembles the behaviour of the optimisation solutions. To be able to evaluate the applicability of this methodology for implementation in vehicles, a small-scale prototype vehicle with force allocation control possibilities has been designed and built. The vehicle is equipped with autonomous corner module functionality that enables individual control of all wheels regarding steering, camber, propulsion/braking and vertical loads. Straight-line braking tests show that force allocation can be used in a real vehicle and will enhance performance and stability even at a very basic level, using few sensors with only the actual braking forces as feedback.

    In summary, this work has contributed to a better understanding of how the allocation of wheel forces can improve vehicle safety, performance and energy efficiency. Moreover, it has contributed to increased understanding of how vehicle motions should be modelled and simulated, and how control strategies for over-actuated vehicles can be made more suitable for implementation in future electrified vehicles.

  • 49.
    Edrén, Johannes
    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, 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.
    Implementation and evaluation of force allocation control of a down-scaled prototype vehicle with wheel corner modules2013In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 8, no 4, p. 335-363Article in journal (Refereed)
    Abstract [en]

    The implementation of wheel corner modules on vehicles creates new possibilities of controlling wheel forces through the utilisation of multiple actuators and wheel motors. Thereby new solutions for improved handling and safety can be developed. In this paper, the control architecture and the implementation of wheel slip and chassis controllers on a down-scaled prototype vehicle are presented and analysed. A simple, cost-effective force allocation algorithm is described, implemented and evaluated in simulations and experiments. Straight line braking tests were performed for the three different controller settings individual anti-lock brakes (ABS), yaw-torque-compensated ABS and force allocation using both wheel torque and steering angle control at each wheel. The results show that force allocation is possible to use in a real vehicle, and will enhance the performance and stability even at a very basic level, utilising very few sensors with only the actual braking forces as feedback to the chassis controller.

  • 50.
    Edrén, Johannes
    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.
    Utilization of Vertical Loads by Optimization for Integrated Vehicle Control2012In: Proceedings of AVEC12, 11th Symposium on Advanced Vehicle Control, September 9-12, Seoul, Korea, 2012., 2012Conference paper (Other academic)
    Abstract [en]

    This paper presents results on how to optimally utilise vertical loading on individual wheels in order to improve vehicle performance during limit handling. Numerical optimisation has been used to find solutions on how the active suspension should be controlled and coordinated together with friction brakes and electric power assisted steering (EPAS). Firstly, it is investigated whether the brake distance can be shortened. Secondly, the performance during an evasive manoeuvre is investigated. The result shows that brake distance can be improved by at least 0.5 m and the speed through the evasive manoeuvre by roughly 1 km/h for the studied vehicle. Quick actuators is shown to give even better performance. These results provide guidance on how active suspension can be used to give significant improvements in vehicle performance.

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