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  • 101.
    Jiao, Lejia
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Vehicle model for tyre-ground contact force evaluation2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Economic development and growing integration process of world trade increases the demand for road transport. In 2008, the freight transportation by road in Sweden reached 42 million tonne-kilometers. Sweden has a tradition of long and heavy trucks combinations. Lots of larger vehicles, with a maximum length of 25.25 meters and weight of 60 tonnes, are used in national traffic. Heavier road transport and widely use of large vehicles contribute to the damages of pavement. According to a recent research by the VTI, total cost of road wear by freight transport in Sweden in 2005 was about 676 million SEK. If the weights of all vehicles were limited to 40 tonnes, according to the new EU rules, the cost of wear in 2005 would have been 140 million SEK less.

    Lots of studies about road damage caused by vehicle have been done since the last decades. It has been found that the dynamic tyre force plays an important role in the damages of pavement. However, the influence of vehicle-pavement interaction on pavement damage has not been investigated to any large extent yet. The aim of this study is to provide suitable computational truck models, study the influence of vehicle-pavement interaction and parameters of vehicle on pavement damage.

    To fulfil the aims, this study presents vehicle models, including quarter, half, full vehicle models and quarter vehicle model coupled with pavement, used to compute the dynamic tyre force. The different models are then compared. Two actual road profiles measured by laser, a smooth one and an uneven one, are used for evaluation. The models are analysed to find out the vehicle parameters that influence the road damage most and to learn about how detailed models are needed.

    It’s found that difference does exist between more detailed models and less detailed ones, and it’s non-negligible. It will increase with the increase of road unevenness. The dynamic tyre force will not be affected much by coupling the pavement, unless the road surface is very uneven or wheel hop exists. On uneven roads, energy mainly dissipates in vehicle suspension. However, on even roads, vibration can be well damped in tyre before it reaches suspension, so most of energy dissipates in tyre. Different components influence the tyre force differently. The influence varies with different frequency range of input signal (road profile) as well. The effects of sprung parts are mainly in low frequency range, while the effects of unsprung parts are mainly in high frequency range. Parameters of vehicle body influence the dynamic tyre force most. The effect of cabin is much smaller compared to vehicle body and unsprung part. Changes in parameters of pavement will not influence the road load, but its resonant frequency. Therefore, the best way to reduce dynamic tyre load is to design a more lightweight vehicle body, softer and better damped suspension.

  • 102.
    Jonasson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Exploiting individual wheel actuators to enhance vehicle dynamics and safety in electric vehicles2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is focused on individual wheel actuators in road vehicles intended for vehicle motion control. Particular attention is paid to electro-mechanical actuators and how they can contribute to improving vehicle dynamics and safety. The employment of individual wheel actuators at the vehicle's four corner results in a large degree of over-actuation. Over-actuation has a potential of exploiting the vehicle's force constraints at a high level and of controlling the vehicle more freely. One important reason for using over-actuated vehicles is their capability to assist the driver to experience the vehicle as desired. This thesis demonstrates that critical situations close to the limits can be handled more efficiently by over-actuation.

    To maximise the vehicle performance, all the available actuators are systematically exploited within their force constraints.  Therefore, force constraints for the individually controlled wheel are formulated, along with important restrictions that follow as soon as a reduction in the degrees of freedom of the wheel occurs. Particular focus is directed at non-convex force constraints arising from combined tyre slip characteristics.

    To evaluate the differently actuated vehicles, constrained control allocation is employed to control the vehicle. The allocation problem is formulated as an optimisation problem, which is solved by non-linear programming.

    To emulate realistic safety critical scenarios, highly over-actuated vehicles are controlled and evaluated by the use of a driver model and a validated complex strongly non-linear vehicle model.

    it is shown that, owing to the actuator redundancy, over-actuated vehicles possess an inherent capacity to handle actuator faults, with less need for extra hardware or case-specific fault-handling strategies.

  • 103.
    Jonasson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Using future path information for improving stability of an overactuated vehicle2009Inngår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 4, nr 3, s. 218-231Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, model predictive control (MPC) is applied for controlling an over-actuated vehicle. The control problem is associated with the distribution of the tyre forces to ensure vehicle stability. The use of MPC is shown to be a suitable method if the vehicle's future desired trajectory is known. Simulation studies conducted show that access to information in advance, even if such information is restricted to only a few seconds, significantly contributes to maintaining vehicle stability. Furthermore, a longer prediction horizon results in earlier actions and stabilises the vehicle even better.

  • 104.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Andreasson, J.
    Investigation of the non-convex force constraints imposed by individual wheel torque allocation2009Artikkel i tidsskrift (Fagfellevurdert)
  • 105.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Andreasson, Johan
    Utilisation of actuators to improve vehicle stability at the limit: from hydraulic brakes towards electric propulsion2009Inngår i: 21st InternationalSymposium on Dynamics of Vehicles on Roads and Tracks, 2009Konferansepaper (Fagfellevurdert)
  • 106.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. Volvo Car Corporation, Sweden .
    Andreasson, Johan
    Modelon AB, Sweden.
    Solyom, Stefan
    Volvo Car Corporation, Sweden.
    Jacobson, Bengt
    Volvo Car Corporation, Sweden.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Utilization of Actuators to Improve Vehicle Stability at the Limit: From Hydraulic Brakes Toward Electric Propulsion2011Inngår i: Journal of Dynamic Systems Measurement, and Control, ISSN 0022-0434, E-ISSN 1528-9028, Vol. 133, nr 5, artikkel-id 051003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The capability of over-actuated vehicles to maintain stability during limit handling is studied in this paper. A number of important differently actuated vehicles, equipped with hydraulic brakes toward more advanced chassis solutions, are presented. A virtual evaluation environment has specifically been developed to cover the complex interaction between the driver and the vehicle under control. In order to fully exploit the different actuators setup, and the hard nonconvex constraints they possess, the principle of control allocation by nonlinear optimization is successfully employed. The final evaluation is made by exposing the driver and the over-actuated vehicles to a safety-critical double lane change. Thereby, the differently actuated vehicles are ranked by a quantitative indicator of stability.

  • 107.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Andreasson, Johan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Global force potential of over-actuated electric vehicles2010Inngår i: International Journal of Vehicle System Dynamics, ISSN 0042-3114, Vol. 48, nr 9, s. 983-998Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper formulates force constraints of over-actuated road vehicles. In particular, focus is put on different vehicle configurations provided with electrical drivelines. It is demonstrated that a number of vehicles possesses non-convex tyre and actuator constraints, which have an impact on the way in which the actuators are to be used. By mapping the actuator forces to a space on a global level, the potential of the vehicle motion is investigated for the vehicles studied. It is concluded that vehicles with individual drive, compared with individual brakes only, have a great potential to yaw motion even under strong lateral acceleration.

  • 108.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Andreasson, Johan
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Modelling and parameterisation of a vehicle for validity under limit handling2008Inngår i: Proceedings of 6th Modelica Conference, 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes how a vehicle model from the VehicleDynamics Library is configured, parameterized and validated for predicting limit handling maneuvers. Especially, attention is given to the selection of subsystem models with suitable levels-of-detail as well the selection of performed measurements and measurement equipment. A strong principle throughout the presented work is component-based design where parameterizations are done on sub-system levels, no tuning on the final vehicle models is made. As a final test, the vehicle model is exposed to a sinusoidal steering input. It turns out that the correspondence between the model used and the real vehicle is acceptable for the driving scenario selected up to the limit of adhesion.

  • 109.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Andreasson, Johan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    Jacobsson, Bengt
    Modelling vehicle dynamics for limit handling: Strategies, experiments and validation2008Inngår i: Proceedings of the 9th International Symposium on Advanced Vehicle Control, AVEC´08, 2008, s. 202-207Konferansepaper (Fagfellevurdert)
  • 110.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Roos, Fredrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Design and evaluation of an active electromechanical wheel suspension system2008Inngår i: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 18, nr 4, s. 218-230Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents an electromechanical wheel suspension, where the upper arm of the suspension has been provided with an electric levelling and a damper actuator, both are allowed to work in a fully active mode. A control structure for the proposed suspension is described. The complex design task involving the control of the electric damper and its machine parameters is tackled by genetic optimisation. During this process, these parameters are optimised to keep the power dissipation of the electric damper as low as possible, while maintaining acceptable comfort and road-holding capabilities. The results of the evaluations carried out demonstrate that the proposed suspension can easily adopt its control parameters to obtain a better compromise of performance than that offered by passive suspensions. If the vehicle is to maintain acceptable performance during severe driving conditions, the damper has to be unrealistically large. However, if the electric damper is combined with a hydraulic damper, the size of the electric damper is significantly reduced. In addition, the design of the electric damper with the suggested control structure, including how it regenerates energy, is discussed.

  • 111.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. Volvo Cars, Sweden.
    Thor, M.
    Steering redundancy for self-driving vehicles using differential braking2017Inngår i: Advanced Vehicle Control AVEC’16 - Proceedings of the 13th International Symposium on Advanced Vehicle Control AVEC’16, CRC Press/Balkema , 2017, s. 23-30Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes how differential braking can be used to turn a vehicle in the context of providing fail-operational control for self-driving vehicles. A vehicle model is developed with differential brake and steering inputs. The model is used to explain the bounds of curvature that differential braking provides and it is then validated with measurements in a test vehicle. Particular focus is paid on wheel suspension effects that significantly influence the obtained curvature. Finally, a model based controller is developed to control the curvature by differential braking. The controller is designed to compensate for the wheel angle disturbance that is introduced as a result of the control event.

  • 112.
    Jonasson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Stability of an electric vehicle with permanent-magnet in-wheel motors during electrical faults2006Konferansepaper (Fagfellevurdert)
  • 113.
    Juhlin, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Assessment of crosswind performance of buses2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    When driving a vehicle on the road, the driver has to compensate continuously for small directional deviations from the desired course due to disturbances such as crosswinds, road irregularities and unintended driver inputs. These types of deviations have a tiring effect on the driver and should therefore be minimised. When the magnitude of these disturbances increases, especially with crosswind, the directional deviation might become so large that the driver will have difficulties in compensating for it, and will thereby affect the traffic safety. The objective of this research work is to increase the understanding of the crosswind sensitivity of buses and to find solutions to the problem of improving the safety of buses with respect to crosswind performance. The work presented in this thesis contributes to increased knowledge about the directional stability of buses under the influence of crosswind gusts through parameter studies using detailed vehicle simulation models, through full-scale experiments and through studies of the effect of steering feel on the subjective and objective evaluation of crosswind performance.

    A natural crosswind gust model has been derived from wind tunnel measurements and implemented in a multi-body dynamics simulation tool. The aerodynamic loads of the crosswind gust model have been applied on a detailed vehicle model and the behaviour of the vehicle model has been studied for various vehicle configurations in both open- and closed-loop manoeuvres. The vehicle model, with parameters corresponding to real vehicle data, has been validated and the agreement with measurements is good. A method for estimating the aerodynamic loads on a bus due to crosswind on a road section is also presented. Aerodynamic loads under real conditions were estimated using this method and these data were thereafter used in a study where the effect of steering feel on the subjective and objective evaluation of crosswind performance was investigated using a moving-base driving simulator, with the aim of finding a relationship between steering feel and crosswind sensitivity.

    The thesis covers the influence of changing chassis-related parameters and aerodynamics-related parameters on the crosswind sensitivity, as well as the influence of the setting of the steering system on the crosswind performance of the driver-vehicle system. The results identify areas of high potential for improving the crosswind sensitivity of buses, such as the centre of gravity location and the yaw moment overshoot at gust entry. Furthermore, the study shows the importance of having a vehicle that facilitates prompt driver corrections for reducing the lateral deviation under crosswind excitation; i.e. it is shown that a steering system with the possibility of changing the yaw rate gradient referencing the steering-wheel input when the vehicle is subjected to a sudden crosswind has a good potential for improving the crosswind performance of the driver-vehicle system.

  • 114.
    Juhlin, Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Eriksson, Peter
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    The effect of steering feel on the crosswind performance of buses - Part I: Subjective assessmentArtikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The steering feel is considered to be an important part of the on-centre handling characteristics of vehicles. Therefore, the steering feel is of interest when improving the crosswind performance of buses. In the present paper a methodology is proposed that utilizes a moving-base driving simulator to study the influence of steering feel on the subjective judgement of bus drivers regarding crosswind performance. Results achieved when using this method show that there exists a correlation between the steering feel and the subjective evaluation of crosswind performance. When the drivers are driving a bus with low crosswind sensitivity, it is shown that low yaw rate gradients are preferred for both the steering wheel torque and the steering wheel angle. For more crosswind-sensitive vehicles, the demand for higher yaw rate gradients increases. That is probably due to the increased need for corrections and the fact that more prompt driver corrections are facilitated by higher yaw rate gradients. It can therefore be concluded that, in order to help the driver in a crosswind situation, it would be valuable to be able to change the steering feel characteristics of the vehicle.

  • 115.
    Juhlin, Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Eriksson, Peter
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    The effect of steering feel on the crosswind performance of buses - Part II: Objective assessment and correlation with subjective judgementsArtikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The steering feel is considered to be an important part of the on-centre handling characteristics of vehicles and therefore of interest when improving the crosswind performance of buses. In this paper a methodology is proposed which uses a moving-base driving simulator for studying the influence of steering feel on the objective judgement of crosswind performance. The results obtained with this method show that there exists a correlation between the steering feel and the objective evaluation of crosswind performance. The objective results show that the lateral deviation due to a crosswind gust is reduced for all levels of crosswind sensitivity when the yaw rate gradients referencing both the steering-wheel angle and the steering-wheel torque are increased, thereby minimising the maximum required steering power. This is in contrast to the subjective results, which showed that low yaw rate gradients were preferred when the centre of gravity was in the most forward position. The results presented in this study imply a great potential in using an adaptive steering system, since the steering feel that objectively is most suitable under crosswind excitation is not subjectively preferred for all the centre of gravity positions.

  • 116.
    Juhlin, Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Eriksson, Peter
    Aerodynamic loads on buses due to crosswind gusts – On-road measurements2008Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 46, s. 827-835Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bus and coach traffic is considered to be one of the safest means of travelling. Still, there is a problem with accidents due to crosswind gusts. Therefore it is a need of improving the crosswind performance of buses. As a part of the work with improving the crosswind performance a method for estimating the aerodynamic loads on a bus when exposed to natural crosswind is proposed. The method is based on measurements of the vehicle response and the tire forces from which the aerodynamic loads are estimated using inverse simulations. The results are also shown to agree well with the results of other studies based on wind tunnel measurements. The estimated aerodynamic loads are intended to be used in a future study on crosswind sensitivity using a moving base simulator.

  • 117.
    Kalakos, Dimitrios
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Westerhof, Bernhard
    Heavy Vehicle Braking using Friction Estimation for Controller Optimization2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis project, brake performance of heavy vehicles is improved by the development of new wheel-based functions for a longitudinal slip control braking system using novel Fast Acting Braking Valves (FABVs). To achieve this goal, Volvo Trucks' vehicle dynamics model has been extended to incorporate the FABV system. After validating the updated model with experimental data, a slip-slope based recursive least squares friction estimation algorithm has been implemented. Using information about the tire-road friction coefifcient, the sliding mode slip controller has been made adaptive to different road surfaces by implementing a friction dependent reference slip signal and switching gain for the sliding mode controller. This switching gain is further optimized by means of a novel on-line optimization algorithm. Simulations show that the on-line friction estimation converges close to the reference friction level within one second for hard braking. Furthermore, using this information for the optimized controller has resulted in reduction of braking distance on most road surfaces of up to 20 percent, as well as in most cases a reduction in air usage.

  • 118. Kanchwala, Husain
    et al.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Vehicle handling control of an electric vehicle using active torque distribution and rear wheel steering2017Inngår i: International Journal of Vehicle Design, ISSN 0143-3369, E-ISSN 1741-5314, Vol. 74, nr 4, s. 319-345Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There are two objectives of this work. First is to develop a detailed mathematical model of a vehicle. The second is to develop a controller which makes the vehicle follow desired dynamic characteristics. Suspension kinematics and compliance characteristics have been obtained from the complex suspension models developed in Adams Car (R). Vehicle roll-pitch interactions and variations of roll and pitch centres with respect to wheel travel are considered. The controller is developed as a combination of force allocation control and active rear wheel steering control. Reference trajectories of vehicle velocity, path geometry and vehicle slip angle are the inputs. The controller transforms these user inputs and generates wheel torques and steering commands. A desired value of yaw rate is maintained by generating a restoring yaw moment from unequal torque distribution, and side slip is substantially reduced by active rear wheel steering controller. Finally simulation results illustrate the suitability of the controller.

  • 119.
    Kittane, Santusht Vasuki
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Harinath, Preetham
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    An evasive manoeuvre assist function for over-reactive drivers2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Previous studies have shown that many drivers are unable to provide the right amount of steering torque when facing an imminent collision with an upcoming obstacle. In some cases, drivers under-react i.e., they provide too low steering inputs and thus collide with the obstacle in front; in other cases, drivers might apply a higher steering input than necessary, potentially resulting in the vehicle leaving the road or losing stability. The EMA function is an active safety feature which has the sole objective of providing steering torque interference when performing such a manoeuvre. The motivation for the thesis work is to overcome some limitations of the existing MA function which does not incorporate the ability to differentiate driver reactions. In this thesis, an Evasive Manoeuvre Assist (EMA) function is designed to adapt to both types of the drivers, by an optimised steering torque overlay. The existing current EMA function is always amplifying the driver steering inputs using a feed-forward controller. The focus of this thesis work is to identify and dene a proper steering sequence reference model for closed-loop feedback control design. A simple single-point preview model is designed first to calculate the reference steering angle. A few test scenarios are set-up using the IPG CarMakerTMsimulation tool. The reference model is then tuned with respect to the amplitude and frequency by batch simulations to obtain the optimal steering prole. A feedback controller is then designed using this reference model. The controller is implemented in a real-time environment, using a Volvo rapid-prototype test vehicle. Preliminary variation tests have shown that the developed controller can enhance both an over-reacting and under-reacting driver's performance during an evasive manoeuvre, by applying assistance/resistance EPAS torque timely. The designed EMA function is shown to accommodate different driver reactions and provide intuitive torque interference. As opposed to the earlier notion that the EMA function only assists the driver with an additional steering wheel torque, it was shown that the optimal steering torque overlay might be in the form of assistance or resistance.

  • 120.
    Kjellsdotter, Frida
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    MBS-modelling of a heavy truck: Modelling and model validation2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    As a result of the accelerating demands for faster development within the heavy vehicle industry, computer aided simulations have become a more important tool in the development process. Simulations can offer faster evaluation of loads acting on the vehicle and more cost effective fatigue life predictions than physical testing, since physical prototypes are not needed for load measurements or fatigue tests. However, accurate fatigue life predictions without physical verification are today a difficult task with many uncertainties, yet simulations are still an important part of modern product development.The objective of this work is to investigate the accuracy of a virtual model of a physical truck. The thesis focuses only on load simulation accuracy, leaving the material uncertainties aside. The vehicle model is built using Adams/Car with two different complexities of the frame model. A part of the work is to investigate how the frame model complexity affects the accuracy of the results.The virtual truck is simulated in a virtual test rig that excites the model with displacement on the wheel hubs to represent the forces induced when the truck is driven on the test track. The process to make a drive signal to the test rig is iterative. Simulations are also performed with the virtual model equipped with tires and driven on a virtual 3D road.Model performance is evaluated using TDDI (Time Domain Discrepancy Index) and pseudo-damage. TDDI evaluates the results in the time domain and the pseudo-damage considers the potential fatigue damage in the time series. A value of the TDDI below 0.3 and between 0.5 and 2 for the pseudo-damage is found good. The accuracy is approximately the same as can be repeated by different test engineers driving the same test schedule with the same vehicle.When iterating using the cab and the front and rear end of the frame as response feedback, the results for the model with the simple frame model show good values of TDDI and pseudo damage for the front end of the frame and the cab. Though the axles and the mid of the frame show poor results. The rear end of the frame does not reach the model performance targets, getting a too low value of the pseudo-damage while the TDDI value is good. The vehicle model with the complex frame shows similar results, when using the same response feedback, although the frame model is not optimized.The full vehicle model driving on 3d-road does not, at present, deliver accurate results. However, the relative damping for the beams, representing the leaf springs, has turned out to highly affect the results. The leaf spring model thus need to be optimized. The complex frame model is not showing results good enough to justify the extra modelling time. The accuracy of the full-vehicle model can be considerably improved by optimizing the model/-s of the wheel suspension and the complex frame model.

  • 121.
    Klinger, Julius
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Automotive Body Structure Assembly: Mass & Cost Saving Potential of Laser Welding Compared to Spot Welding2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Due to the continuously increasing demands on the efficiency of road passenger vehicles the National Highway  Safety Traffic Administration (NHTSA)  commissioned a project to determine the achievable mass savings on an average, mass produced passenger car which are obtainable with today’s or within close reach technology. The major part of this project is conducted at EDAG, Inc. One of the approaches made within this program is to reduce the weight of a vehicle’s body struc- ture by replacing the commonly on a mass production vehicle applied joining technology resistance spot welding with laser beam welding. The main advantage is the possibility to bisect the size of the flanges since laser welding requires less flange width compared to spot welding. A sample structure is remodeled twice to create one almost solely spot welded and one almost solely laser welded body structure of the same vehicle. Those body structures are represented by two FEM models. Proper representation of the joining technology is applied to both FEM models in preparation of NVH com- putation runs, ensuring the comparability of the two body structures regarding their performance. In cooperation with experienced production engineers two assembly layouts for the spot welded and the laser welded structures are developed. For those assembly layouts cost calculations are done to oppose the attained mass savings to the increase in production costs. The weight difference between the two versions is determined to a remarkable 12.2 kg for the ana- lyzed sample structure. The laser welded structure thereby displays a slightly improved NVH perfor- mance compared to the spot welded structure. Taking the exemplary cost increase for the assembly of certain parts of the lower body structure into account gave a weight saving efficiency of 4.58 $ per saved kg. For the field of automotive engineering this is a rather high value, mainly caused by the still very extensive costs for laser welding equipment. With laser welding technology being more and more  adopted in mass production applications and most probably due technical improvements those costs are likely to decrease within the next few years. Even more mass savings could be achieved by adapting the design of the body structure more to the usage of laser beam welding.

  • 122.
    Korres, Michael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Cylinder Pressure Sensor based Engine Combustion and Fuel System Diagnostics2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Nowadays, the developed diagnostics models and software are not capable of locating the root cause of an emerging malfunction, or in other words the responsible component, while the vehicle is up and running. In most cases they are solely able to provide the driver with indications that a fault has been detected within a group of components. Subsequently, it is unavoidable that the vehicle returns to the workshop for a number of standardized tests to be performed, in order to evaluate the condition of the potentially faulty components. The new era in combustion engines and the attempt to fully incorporate closed-loop combustion control can facilitate the diagnostics procedure and especially the process of fault isolation. By harnessing signals from both real and virtual sensors, it can be feasible to diagnose or even prognose faults, averting the return of the vehicle to the workshop. Moreover, the down-time of the vehicle, can be radically decreased, since there will be an indication on which components to focus. Taking into account the fastpace steps and improvements on the respective hardware, such as sensors, one can understand that this endeavour can actually be successful in the future. In the spectrum of this thesis it is assessed whether or not fault detection and isolation can be achieved, through comparison of sensors’ output signals for a number of engine parameters to a stored set of nominal values for these parameters (reference values). Towards that goal, virtual sensors have been developed with the aid of measurement data, in order to increase the reliability of the system.

    Subsequently, a network of dependencies between parameter values and consequent malfunctions has been constructed, in the form of flowcharts, rudimental for fault isolation. In addition to that and despite the fact that no finalized production code for the model is provided, pseudocode charts have been created as well. Finally, significant effort was made to derive precise tolerances for the reference values, as this is of great importance for the results of the diagnostics model.

  • 123.
    Kovacevic, Igor
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Modelling and simulation of the three-wheeled urban concept vehicle Smite2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis treats the handling analysis of the Vehiconomic's three wheeled prototype vehicle "Smite". This is a light weight low emission vehicle intended for urban traffic but with sufficient power supply to manage highway driving as well. The purpose of this thesis is to evaluate the vehicle's stability and handling characteristics using the multibody simulation software ADAMS/Car, and also to try to find a more optimum configuration of the vehicle. The software in an excellent tool that allows you to examine different driving scenarios and easily make vehicle modifications, both quicker and safer than in real life.

    In order to obtain reliable results the simulations have to be as close to the reality as possible. The ADAMS/Car model was validated with the help of logged data, derived while performing physical test runs on an air strip. Maneuvers preformed were; Severe lane change, Slalom maneuver and a J-turn maneuver. Due to simplifications made in the virtual model, the validation did not generate satisfying results for all driving scenarios, but the model is considered good enough to help draw general conclusions about the vehicle's behavior. The largest simplification made was regarding the propelling of the vehicle, which was made front wheel driven instead of rear wheel driven.

    Due to the simple construction of the vehicle, very little room for modifications is available. The possibilities to affect the position of the center of gravity are very limited. The only room for modification available is in the front suspension system. Due to multiple mounting points for the spring/damper component, 12 different combinations of the front suspension system were generated. Additionally two more setups were made by changing the track width with the implementation of spacers. A suspension configuration was found that reduced the roll angle with approximately 10%.

  • 124.
    Kurzer, Karl
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för industriell teknik och management (ITM), Centra, Integrated Transport Research Lab, ITRL.
    Path Planning in Unstructured Environments: A Real-time Hybrid A* Implementation for Fast and Deterministic Path Generation for the KTH Research Concept Vehicle2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    On the way to fully autonomously driving vehicles a multitude of challenges have to be overcome. One common problem is the navigation of the vehicle from a start pose to a goal pose in an environment that does not provide any specic structure (no preferred ways of movement). Typical examples of such environments are parking lots or construction sites; in these scenarios the vehicle needs to navigate safely around obstacles ideally using the optimal (with regard to a specied parameter) path between the start and the goal pose. The work conducted throughout this master's thesis focuses on the development of a suitable path planning algorithm for the Research Concept Vehicle (RCV) of the Integrated Transport Research Lab (ITRL) at KTH Royal Institute of Technology, in Stockholm, Sweden. The development of the path planner requires more than just the pure algorithm, as the code needs to be tested and respective results evaluated. In addition, the resulting algorithm needs to be wrapped in a way that it can be deployed easily and interfaced with di erent other systems on the research vehicle. Thus the thesis also tries to gives insights into ways of achieving realtime capabilities necessary for experimental testing as well as on how to setup a visualization environment for simulation and debugging.

  • 125.
    Kölzow, Krister
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Method for rebuilding gaspoweredtrucks2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis investigates the possibility to rebuild heavy-duty trucks poweredby liquefied natural gas (LNG) to other fuel options such as compressednatural gas (CNG), diesel or ethanol. The background is that the second handvalue for a LNG truck is lower than a similar diesel truck due to an undevelopedinfrastructure with few refuelling stations. This results in a small market for secondhand LNG trucks.Both tractor and rigid trucks are evaluated from a technical perspective to determinewhich components that need to be changed when switching from LNG toanother type of fuel. When that is completed each fuel alternative is evaluatedbased on cost and market interest. Also certification and other legislations areinvestigated to determine if they will affect the rebuilding process.The result shows that the rebuild faces different technical complexity dependingon the target fuel alternative. It is concluded that a rebuild to diesel or ethanolis expensive due to many changes needed for the engine and aftertreatment andtherefore these alternatives are not a good choice for a rebuild. A rebuild to CNGis still expensive but can be of interest for rigid trucks, but not for tractor truckssince they usually have a demand for longer range. In order to get the final cost ofthe rebuild to CNG a commercial assessment has to be made and the rebuild willdepend on in which country the rebuild is performed due to different legislationsfor re-registration which may be a an obstacle.

  • 126.
    Laporte, Rémy
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Hybrid Electric PowertrainComparative Study2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    New trends for environmentally-friendly mobility are rising and expectations derived from customers are significant. Urban areas such as London or even Stockholm are starting to build urban tolls by charging conventional vehicles while full‐electric powered vehicles are exempted. Carbon taxes will be certainly introduced at the EU scale in the next decade, which will strengthen those expectations of   transportation  changes  especially  regarding  private  vehicles.  High  electrification  degree  of conventional  vehicles  has  to  be  performed  to  answer  to  those  expectations.  To  avoid  range restriction mainly related to the energy content limitations in battery electric vehicles (BEV), fuel tank has to be kept in conjunction with internal combustion engine. Thereby, according to this statement, the design of either a plug‐in hybrid electric vehicle (PHEV) or a range extender (REX) in a second extent with an extensive full‐electric range is relevant in the next decade.

  • 127.
    Lesser, Martin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Karlsson, Lennart
    Luleå Tekniska Universitet .
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    An interactive model of a pantograph-catenary system1996Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 25, s. 397-412Artikkel i tidsskrift (Fagfellevurdert)
  • 128.
    Li, Shiruo
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Camber effect study on combined tire forces2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Considering the more and more concerned climate change issues to which the greenhouse gas emission may contribute the most, as well as the diminishing fossil fuel resource, the automotive industry is paying more and more attention to vehicle concepts with full electric or partly electric propulsion systems. Limited by the current battery technology, most electrified vehicles on the roads today are hybrid electric vehicles (HEV). Though fully electrified systems are not common at the moment, the introduction of electric power sources enables more advanced motion control systems, such as active suspension systems and individual wheel steering, due to electrification of vehicle actuators. Various chassis and suspension control strategies can thus be developed so that the vehicles can be fully utilized. Consequently, future vehicles can be more optimized with respect to active safety and performance.

    Active camber control is a method that assigns the camber angle of each wheel to generate desired longitudinal and lateral forces and consequently the desired vehicle dynamic behavior. The aim of this study is to explore how the camber angle will affect the tire force generation and how the camber control strategy can be designed so that the safety and performance of a vehicle can be improved.

    As the link between the vehicle and the road, the tire ultimately determines the dynamic characteristics of the vehicle. Researchers in the automotive industry have developed various tire models to describe the force and torque generation of a tire. The semi-empirical Magic Formula tire model and the simple physical brush tire model are two common and widely used tire models.

    In this study, a quick review of the Magic Formula tire model and the brush tire model is firstly presented. Bearing the advantages and disadvantages of the two models in mind, a new multi-line brush tire model, which places its focus on camber effect on longitudinal and lateral force generation, is developed according to the brush model theory. The newly developed multi-line brush tire model describes longitudinal and lateral force generation at different camber angles accurately and provides some essential information of the effect of camber angle.

    However, the multi-line brush tire model consumes huge amount of computational effort thus it is not suitable for real time vehicle level simulations. In order to explore how the camber control strategy can be designed, a simple magic formula model is developed by curve fitting to the multi-line brush tire model. The simple magic formula model takes much less computational effort but represents the force generation at different camber angles quite well as the multi-line brush tire model does. With the help of the simple magic formula model, real time vehicle level simulations are conducted to find the optimal camber control strategies with respect to safety and performance.

  • 129.
    Ljungberg, Marcus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Electric power assist steering system parameterization and optimization employing CAE2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The vehicle brands of today need to develop high quality products in a short period of time to satisfy the consumer needs and to stand out in the competition. To be able to do this simulation tools have been used more and more in the development process. This would enable quick evaluation of different concepts and setups without the need of building physical prototypes (though physical prototypes are still common to validate development in different stages). The goal of this thesis is to contribute to this trend by developing and evaluating a process of optimizing the control parameters of an EPAS (electronic power assist steering) system by solely using computer aided engineering (CAE) tools. This tuning is done to improve the steering feel for the driver. The process could then be used to improve the initial tuning of such a system or in a later stage completely parameterize it.

    In this project, a complete process from setting up the simulation environment to developing the optimization process of the parameters was developed. A vehicle model was simulated using the real time simulation software IPG CarMaker, parameterized by multi-body simulation results and tyre measurements. The steering system itself was modelled by the supplier in Simulink so that the entire vehicle could be co-simulated using both CarMaker and Simulink. To evaluate the performance of the steering system objective metrics were used, each of which had a target range.

    The optimization process itself utilizes the optimization tool Tomlab, which is a powerful Matlab toolbox. Tomlab uses a complex strategy of evaluating the response of a system when the relationship between the inputs (in this case the EPAS control parameters) and the outputs (in this case the objective metrics) is unknown. A cost function using the difference between the target metric value and the actual metric value was set up and the weighing factors for each of the tested metrics were determined by their sensitivity to the optimized parameter.

    The developed process was tested on three specific metrics for two specific parameters of the controller. These metrics were the friction feel, the torque build-up and the torque deadband, all three of which relates to the torque feedback of the steering wheel.

    All three metric values had room for improvement but after going through the developed process they could be adapted to be closer to the optimal target. These results need to be validated, but as a proof of concept the work described in this thesis shows that it is possible to parameterize a vehicle subsystem by only using CAE tools.

  • 130.
    Ljungberg, Marcus
    et al.
    Volvo Car Corporation.
    Nybacka, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Gil Gómez, Gaspar
    Volvo Car Corporation.
    Katzourakis, Diomidis
    Volvo Car Corporation.
    Electric Power Assist Steering System Parameterization and Optimisation Employing Computer-Aided Engineering2015Inngår i: Steering and Suspension Technology Symposium, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The automotive industry strives to develop high quality vehicles in a short period of time that satisfy the consumer needs and stand out in the competition. Full exploitation of simulation and Computer-Aided Engineering (CAE) tools can enable quick evaluation of different vehicle concepts and setups without the need of building physical prototypes. Addressing the aforementioned statements this paper presents a method for optimising the Electric Power-Assisted Steering (EPAS) ECU parameters employing solely CAE. The objective of the optimisation is to achieve a desired steering response. The developed process is tested on three specific steering metrics (friction feel, torque build-up and torque deadband) for two function parameters (basic steering torque and active return) of the EPAS. The optimisation method enabled all metrics to fall successfully within the target range. 

  • 131.
    Lorente, Alejandro
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Suspension analysis and development of prospective Formula Student racing car2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    For racing the best engine cannot win any race without a very good suspension system. However the best suspension system with a decent engine is a stronger combination. Power without control is useless, so a suspension system is as important. After testing the previous cars with ADAMS software, the first results showed problems and demanded some redesign.

    To correct these problems the relation between the wheel movement and the spring movement should be linear. It sounds like a basic problem but it is preferable to have a linear relationship between both two. Otherwise the vehicle will be hard to set up properly and the car could even be unstable when the forces are higher. Hence, the first part of the work has been to focus on the front and rear suspension independently.

    Next step consisted of building a full vehicle assembly model to study the influence of other factors for the full vehicle. During a race when the car is going straight the most important components are the engine and tyres (as Formula Student racing car does not reach really high speed aerodynamics is not as important as the other two). However, when tuning the car one of the most important system of the car is the suspension system and how it interacts with the tyres. To improve the suspension performance it will be necessary to pay attention to parameters that influence the stability of the car and the performance concerning maximum lateral acceleration. Better cornering performance will be translated to faster lap time at a race.

    The final part of the work was to test the car for other condition and for other manoeuvres, e.g. acceleration out of corner and braking or throttle release into the corner. All these different situations will give the Formula Student team more information about how the car will perform during different situations. To find a suitable setup with the constraints that were given a Design of Experiment (DOE) study was performed, varying suspension points, stiffness of anti-roll bars, camber and toe angles.

  • 132.
    Luco, Nicolas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Zhu, Keren
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Energy efficient cornering: Simulation and verification2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this master thesis is to study the energy efficiency of a vehicle when it is cornering. To achieve this, a Simulink model was built from a simple basic bicycle model and theoretically validated. This model was then analysed and successively improved by adding velocity and yaw moment control. A study of the vehicle model behaviour by changing parameters such as cornering stiffness and centre of gravity position was the nconducted. The traction force needed for a constant radius was calculated and methods such as torque vectoring have been tested using the model to obtain the lowest traction force. The model was compared with different vehicle types and further validated by comparing the simulation results with experimental data acquired from a field test. The rolling resistance and aerodynamic resistance were taken into account when the model was validated with the experimental data and the result suggest that by distributing the required traction force (using torque vectoring between inner and outer driven wheels) the energy efficiency could be improved by 10%. This report ends with recommendations for future work.

  • 133.
    Lundberg, Ted
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Analysis of simplified dynamic truck models for parameter evaluation2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The ride comfort in heavy commercial trucks is an important property that requires detailed testing to investigate how different vehicle components affect the response to road input. Trucks come in many different configurations and a customer purchasing a new truck often has the choice to specify number of axles, drive line and cabin type, type of suspension and so on. This gives that there are many vehicle variations that have to be tested to ensure good ride comfort. Testing many combinations of, for example, dampers in different environments and road conditions might be time consuming. The work could be helped by pre-test computer simulations where the vehicle is simulated with the same conditions as in the tests. The simulation results could then be used to better understand how different components affect the vehicle response to a certain road input.

    By using a MultiBody System (MBS) software, a full truck could be modeled and simulated to acquire accurate results. The simulation would however be computationally demanding and take long time. It also requires that the test engineer is familiar with the MBS software to be able to create the model and run the simulations. This thesis focuses on investigating if simplified dynamic truck models developed in Matlab could be an alternative to more complex models created in an MBS software.

    Three different models are developed: a quarter car model, a 2D half truck model and a 3D truck model. The models are derived using the Lagrangian energy method and the dynamic response from a given road input is calculated numerically in Matlab. Different methods of solving the systems of differential equations are discussed and the implementation of the implicit Newmark -method is explained. To validate the truck models and solver, the models are replicated in the MBS software Adams View. The response of the Adams and Matlab models from an excitation on the wheels are compared to determine that the equations and solver are correctly derived and implemented. To test the models capabilities to predict the response in a real truck, tests on a road simulator are performed. A four-wheel Scania tractor is tested in a hydraulic road simulator rig. The road simulator excited the truck through the wheels with a sinus sweep from 0-20 Hz and the resulting accelerations in the tractor are measured. Three different setups of front axle dampers are tested to get a parameter variation to study with the models: a standard damper, harder damper and undamped front axle. The same tests are simulated in Matlab and the acceleration responses are compared to see how well the models predict the accelerations seen in the real truck.

    The models in Matlab and Adams give the same results and are therefore reasoned to be mathematically correct. The Newmark -method is efficient and gives reasonable computing times. In the comparison with the road simulator test the models do not give the same results as measured on the truck. To be able to compare the results from the measurements and simulations, the tire stiffnesses have to be trimmed so that the correct eigenfrequency of the axles are found. The results with modified tire stiffnesses give better results but still with considerable deviations from the experimental results. The measurements on the truck show that the eigenfrequency of the front axle decrease when removing the front axle damper while the models show that the eigenfrequency increase. Also there are differences in the acceleration measured in the cabin and frame as the models do not predict many of the higher eigenfrequencies.

    In conclusion it is discussed that the models have to be more complex to give useful information about the effects of variation of dampers on the axles. It is also discussed that using commercially available software to perform the same simulations might be a better alternative that gives the user more freedom to overlook and make changes to the model.

  • 134.
    Manzari, Luca
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Göransson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Cuenca, Jacques
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Lopez Arteaga, Ines
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    A fully automated high-speed optical rig for in vacuo, full field, non-contact vibration measurements for viscoelastic, anisotropic materials2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a setup for measuring the three-dimensional displacement field of a test object un-dergoing controlled dynamic excitation in a vacuum chamber is presented. The setup has beendesigned with porous materials in mind, yet is suitable for the measurement of anisotropic vis-coelastic solids in general. To achieve non-contact data acquisition, a stereo high-speed camerasystem measures the displacement of the foundation and of the test object. A laser Doppler vi-brometer is used before the actual measurement to choose an excitation level that maximizes thesignal-to-noise ratio while allowing to ensure that the test object is fully relaxed and stable at thebeginning of every measurement. The setup, comprising both commercial and in-house hardwareand software solutions, addresses the challenges of measuring in vacuum with non-contact tech-niques. All these aspects are discussed in the current paper, and preliminary results are presented.The ultimate objective is to estimate the dynamic properties of a material using inverse methodsand the data obtained.

  • 135.
    Massolo, Mathieu
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Influence of performance degradation on vehicle dynamics2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Technology&Strategy is a French-German consulting company based in Strasbourg, France. Most of its activities take place in the automotive sector with many of their consultants working for Bosch Chassis Control in Abstatt, Germany. Bosch Chassis Control is responsible for the development of active safety control systems for many car manufacturers worldwide. The ESP (Electronic Stability Program) was created by Bosch and is now compulsory in every European car since 2014. The development of the ESP includes an portant part of onboard testing before the production release.

    The application team is responsible for achieving those tests and analyzing the data recorded. One of the features of the ESP is the TCS (Traction Control System) allowing the vehicle to remain at its maximum friction available depending on several parameters such as road friction, speed or wheel angle. The goal of this master thesis is to study the control logic of the TCS and highlight the inuence of several parameters from the software to the vehicle dynamics. The rst part of this thesis was dedicated to the development of a MATLAB tool used to visualize measurements out of di erent test sessions on the same plot. The current tool used is limited to a single measurement display.

    The second part focuses on the analysis of TCS data taken through several test sessions with di erent parameters. The two main controllers of the TCS, PTC and BTC (Powertrain Traction Control and Brake Traction Control) are the core of this analysis.

  • 136.
    Mohammadi, Mahdi
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Ngeno, Ray
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Analysis oft yre wear using the expanded brush tyre model2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Approximately 60 000 tonnes of tyres are produced annually in Sweden to meet thedemand in the market. It is believed that 10 000 tonnes of rubber particles contaminatesthe Swedish roads every year. Some of the elements in the emitted particles cannegatively impact the environment. These elements can lead to leaching in water thatcan cause serious problems to aquatic organisms. Furthermore worn out tyres negativelyinfluence the driving dynamics. It increases the risk of aquaplaning which can have fatalconsequences. Innovative ways of recycling tyres are constantly being developed butstill faces major challenges. It is therefore important to understand tyre wear, whatinfluences it and how to reduce it.

    The aim of the project is to acquire knowledge related to tyre wear, its environmentalimpacts, use a mathematical model to simulate tyre wear and study how the differentparameters influences wear.

    First a literature survey was performed to acquire knowledge related to tyre wear. It wasfound that tyre wear is mainly due to adhesive and hysteresis wear. Several factors werefound to affect tyre wear for example velocity, slip angle and the type of road surface.The environment impact was also studied and the results show the composition of theparticles emitted to the environment. Some of the emitted particles negatively affect theaquatic organism and human beings.

    In the second part of the project a mathematical model based on the well-known brushtyre model was used to simulate how wear changes with different parameters. Themodel created at KTH Vehicle Dynamics is named the expanded brush tyre model(EBM). The wear model chosen for this evaluation was the Archards wear law. Thismodel was used to be able to quantify wear and study how it is influenced by differentfactors.

    The result of the mathematical models shows clearly an exponential increase in thevolume of wear with increases in velocity, slip angle and vertical load. The analysis wasdone using zero camber angle.

    For future work it is recommended to investigate camber angle as it is also one of themajor factors that affects wear. Temperature is also another factor that was not taken into account in the study. It can also be studied in future work.

  • 137. Morales Sanchez, Francisco
    et al.
    Wideberg, Johan
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Problems in using individual X-by-wire cornering modules2014Inngår i: International Journal of Heavy Vehicle Systems, ISSN 1744-232X, Vol. 21, nr 1, s. 1-10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article discusses some mechanical problems which occur by using hub-motors and individual wheel steering on road vehicles. Several multi-body dynamic simulations have been done in order to illustrate the high reaction forces in the steering actuator. This paper is not about an individual steering or control per se but aims to analyse the different forces in a given steering system for different steering scenarios.

  • 138.
    Mounzer, Raid
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Improving simulators’ driving experience through objective metrics and subjective assessments2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

     As the challenge grows in the vehicle industry, tightening the margins on financial and environmental costs of the vehicle development, computer aided engineering becomes more and more attractive. Extensive work is being invested in creating detailed models that can replicate vehicle behaviour accurately and efficiently. The work in this thesis starts with studying objective and subjective evaluations of vehicles as well as their counterparts in vehicle models and a simulator environment. Then, it continues to locate the weaknesses in the models, and investigate the possible improvements. The first part of the thesis focused on performing a literature study concerning the objective metrics and their use in the vehicle industry, as well as the use of simulators. This served as a foundation for the use of objective metrics in the validation of the CarRealTime models. The tools used in the thesis were also introduced. The work continued with the study of previously collected data concerning vehicle evaluation through subjective assessment and objective metrics, with different anti-roll bar configurations, to build trust in the ability of the drivers in evaluating these criteria. Similar data from the CarRealTime models and the simulator were also studied. The aim was to evaluate the simulator driving experience accuracy through the subjective assessment. The weaknesses of the model were identified, and an improved steering model was introduced, replacing the old lookup tables with a Pfeffer model from CarRealTime combined with the steering assist unit in Simulink. An extensive parameter study was performed to understand the effect of selected parameters on the driving experience. Using the same model, the simulator delays were studied in terms of replicating yaw and lateral movements, and how this can affect the driver’s perception of the driving experience. Finally, the results from the parameter study were used to assign the weight parameters in the optimization objective function where the goal was to study the possibility of improving the accuracy of the driving experience as well as counteracting the effects of simulator delays. The Matlab Optimization Toolkit was used in the process. As a conclusion, it was shown that the subjective assessment together with the objective metrics played a crucial role in identifying model and simulator weaknesses. The parameter study showed promising opportunities in solving the aforementioned issues, with the optimization tool and boundaries needing more elaborate work to reach conclusive results.

     

  • 139.
    Muhieddine, Hassan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Suspension System Dimensioning and Modelling for Co-Simulation with Simulink and Adams2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis addresses the dimensioning of a hydraulic suspension system for a hybrid forest truck (HFT) under development. Furthermore, the suspension system has been modelled in MATLAB/Simulink and an environment has been set-up for a cosimulation with the vehicle model in MSC Adams. The interface between the programs has been determined and the required preprocess is described, step by step. Numerical problems and challenges that have arisen have been discussed, together with recommendations for how they could be solved.

    The purpose of the co-simulations have been to analyse the vehicle vibration levels and tune component parameters, such that, the international standard for whole-body vibrations, ISO 2631-1 (1997) and AFS 2005:15 (2005) can be met. The results are presented and clearly shows that the vibration levels in the vehicle cab are acceptable according to the standards. Moreover, recommendations are given for future work regarding how cosimulation problems could be solved, but also how to develop this passive suspension system to be of active type.

  • 140.
    Mårtensson, Jonas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nybacka, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Jerrelind, Jenny
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Evaluation of Safety Distance in Vehicle Platoons by Combined Braking and Steering2012Inngår i: Proceedings of 11th International Symposium on Advanced Vehicle Control, Sept 9-12, 2012, Seoul, Korea, Japan Society of Mechanical Engineers (JSAE) , 2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Platooning is a way to increase the traffic flow and capacity on roads to handle the upcoming problems of traffic congestion and exhaust emissions. The aim with this work is to evaluate if the safety distance of platooning vehicles can be further reduced when both lateral and longitudinal control is implemented. The idea is that when the vehicle in front suddenly brakes the vehicle behind, if needed, is steered aside while braking and stops beside the preceding vehicle. The analysis is performed using a game theoretical approach and different detailed vehicle models. Results show that the safety distance can be reduced.

  • 141.
    Nilsson, Andreas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Agebro, Markus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Study of path tracking skill and strategy using a moving base simulator2007Inngår i: FISITA’06 World Automotive Congress, 2007Konferansepaper (Fagfellevurdert)
  • 142.
    Nilsson, Andreas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    A path tracking scenario without preview for analysis of driver characteristics2008Inngår i: Proceedings of the 9th International Symposium on Advanced Vehicle Control, 2008Konferansepaper (Fagfellevurdert)
  • 143.
    Nilsson, Andreas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Methodology to find parameters characteristic to path tracking skill: DLC-test in a moving base simulator2009Inngår i: Proceedings of the 21st International Symposium: Dynamics of Vehicles on Roads and Tracks, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objective of this work is to evaluate the driver skill relation to a large number of objective vehicle parameters, all measured in a moving base simulator used in the test. Recruitment of High skill and Low skill drivers is done based on self evaluations by the drivers in relation to driver type descriptions. A moving base simulator with a double lane change (DLC) scenario is used both for recruitment verification and measurement of parameter metrics. Here, a suggested method that is used for the comparison of measures under equal conditions is described, and the best separation between the two recruited driver types is found for the highest velocity with all drivers participating, 70 km/h, in the second part of the manoeuvre, e.g. by using standard deviation of steering wheel rate or angular acceleration.

  • 144.
    Nilsson, Erik
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Radikalt förkortad bromssträcka En jämförelse av okonventionella nödbromsmetoder för vägfordon2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 145.
    Noréus, Olof
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Improving a six-wheeler’sperformance both on- and off-road2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In vehicles with electric transmission and independent wheel stations, there is apossibility to control propulsion, steering and suspension individually for eachwheel. This makes it possible to improve mobility in terrain as well as performanceand driving safety on road. This contribution concerns how a six wheeledelectric transmission vehicle should be modelled to enable evaluation of thedynamic behaviour both in terrain and on road. This is made by combiningmodelling of vehicle, transmission and tyre/terrain behaviour.A tyre/terrain model is needed to simulate driving on soft ground. Heretyre/terrain models for simulating driving with both rigid and pneumatic wheelson soft ground have been developed. A method to measure terrain parametersand drawbar pull for a six-wheeled vehicle on sand is proposed, tested andevaluated.To simulate a six wheeled vehicle at the handling limit on road, a vehicle modelwith a brush tyre model is used in order to get physically reasonable simulationresults during high combined slip conditions. Different vehicle configurationsare considered, where front wheel steering is combined with eithersecond axle steering, rear wheel steering or individual wheel torque control.By applying different vehicle slip angles and thereby limiting the DOF of thevehicle model, the vehicle configurations are evaluated during different drivingconditions. The results show that by applying individual torque control to thefront wheel steered vehicle, the performance is improved for all evaluated manoeuvres,and the achievable aligning torque during a rear wheel skid increasessignificantly if the vehicle slip angle is larger than the maximum front wheelsteering angle.To conclude, models of a six-wheeled vehicle with electric transmission andtyre models both for soft and rigid ground have been developed. These modelsform a simulation platform, which makes it possible to evaluate controlstrategies for the electric transmission with the purpose to improve mobility interrain as well as performance and driving safety on road. Some examples ofapplications of the models are included, e.g. improving at-the-limit handlingand pivot turning performance.

  • 146.
    Noréus, Olof
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Comparison of measured and simulated drawbar pull forsix wheeled vehicle with radial pneumatic tyres on sandInngår i: Journal of terramechanics, ISSN 0022-4898, E-ISSN 1879-1204Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    To enable improved cross country characteristics of wheeled vehicles with individually controlled transmission on soft ground,suitable tyre/terrain models are needed. Here tyre/terrain models for simulating driving with both rigid and pneumatic wheels onsoft ground have been developed. A method to measure terrain parameters and drawbar pull for a six-wheeled vehicle on sand isproposed, tested and evaluated. The method is developed in order to be able to validate the proposed tyre/terrain models includingboth rigid and pneumatic wheels that are developed to simulate the behaviour of a six-wheeled vehicle with electric transmissionon soft ground. Tests were performed at different tyre pressures, and it is shown that the drawbar pull is vastly improved atlower tyre pressures. Since the tyre/terrain model uses terrain parameters such as pressure–sinkage and shear stress–displacementrelationships, the sand properties are measured with a Bevameter. Parameters in the pressure–sinkage relationship are estimated tofit the measured data. Both external and internal shearing properties of the sand are measured using a rubber coated shear ring anda shear ring with grousers, respectively. Shear curves of simple exponential form from the developed tyre/terrain models are shownto agree reasonably well with the measured shear behaviour. This will be the base in the development of a strategy to get improvedcross country characteristics of six-wheeled vehicles.

  • 147.
    Noréus, Olof
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Control of at-the-limit handling behaviour of a six-wheeler: strategies based on individual steer and individual torque controlInngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    To simulate a six wheeled vehicle at the handling limit, a vehicle model with a brush tyre model is used in order to get physicallyreasonable simulation results during high combined slip conditions. Different vehicle configurations are considered, where frontwheel steering is combined with either second axle steering, rear wheel steering or individual wheel torque control. By applyingdifferent vehicle slip angles and thereby limiting the DOF of the vehicle model, the vehicle configurations are evaluated duringdifferent driving conditions similar to for example front wheel skidding and rear wheel skidding. The results show that by applyingindividual torque control to the front wheel steered vehicle, the performance is improved for all evaluated manoeuvres, and it is theonly method among the evaluated methods that significantly increases the achievable aligning torque during a rear wheel skid if thevehicle slip angle is larger than the maximum front wheel steering angle. Rear wheel steering, on the other hand, has negligibleeffect on the aligning torque during a rear wheel skid for the six-wheeler.

  • 148.
    Noréus, Olof
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Measurement of terrain values and drawbar pullfor six wheeled vehicle on sand2008Inngår i: 16th International Conference of the International Society for Terrain-Vehicle Systems, Turin, 2008Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A method to measure terrain parameters and drawbar pull for a six-wheeled vehicle on sand is proposed,tested and evaluated. The method is developed in order to be able to validate previously proposedtire/terrain models that are developed to simulate the behaviour of a six-wheeled vehicle withelectric transmission on soft ground. Tests were performed at different tire pressures, and it is shownthat the drawbar pull is vastly improved at lower tire pressure. Since the tire/terrain model uses terrainparameters such as pressure–sinkage and shear stress–displacement relationships, the sand propertiesare measured with a Bevameter. Parameters in the pressure–sinkage relationship are estimated to fitthe measured data. Both external and internal shearing properties of the sand are measured using arubber coated shear ring and a shear ring with grousers, respectively. The measured shear behaviouris shown to agree reasonably well with shear curves of simple exponential form. This will be a basein the development of a strategy to get improved cross country characteristics of six-wheeled vehicleswith individually controlled electric transmission on soft ground.

  • 149.
    Nybacka, Mikael
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    He, Xuxin
    Gil Gómez, Gaspar
    Volvo Car Corporation.
    Bakker, Egbert
    Volvo Car Corporation.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Links between subjective assessments and objective metrics for steering2014Inngår i: International Journal of Automotive Technology, ISSN 1229-9138, E-ISSN 1976-3832, Vol. 15, nr 6, s. 893-907Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The characteristics of steering perception are decisive factors for overall driver preference and for vehicle safety. Car manufacturers are continuously required to tune the characteristics of the vehicle and have a strong need to be more effective in the design and evaluation of cars. Using only objective metrics (OM) can result in unwanted steering feel and using only subjective assessments (SA) is time-consuming, costly and non-repetitive. Before a tool can be built to predict the steering feel in front-end development and to improve design knowledge from the full vehicle level to the component level, links between subjective assessments and objective metrics must be found and analysed. The data collected for the study presented in this paper include subjective ratings from expert drivers and objective measurements made with steering robots, involving twelve expert drivers and over twenty vehicles across four different vehicle classes. Linear regression and neural network analysis (NN) have been used to explore reliable subjective-objective links. The tools and methods used in this research showed promising results. Most of the links found concern response and torque feedback. The preferred ranges of some crucial objective metrics leading to more desirable steering feel have been defined and presented. The results indicate that it would be possible for car manufacturers to develop new vehicles more effectively with a steering feel in line with the design criteria by using the tools and methods investigated in this paper. 

  • 150.
    Nybacka, Mikael
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    He, Xuxin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Su, Zhicheng
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Bakker, Egbert
    Volvo Car Corporation.
    LINKS BETWEEN SUBJECTIVE ASSESSMENTS AND OBJECTIVE METRICS FOR STEERING AND DRIVER RATING EVALUATION2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    During development of new vehicles finding correlation links between subjective assessments and objective metrics is an important part in the vehicle evaluation process. Studying different correlation links is of importance in order to make use of the gained knowledge in the front end of development, during testing and for new systems. Both subjective assessments using the rating scale of 1-10 from expert drivers and objective metrics from different tests measured by a steering robot were collected by standard testing protocols at an automotive manufacturer. This paper evaluates driver ratings and analyse correlations by using Regression Analysis and Neural Networks through a case study approach. Links have been identified and are compared to related research.

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