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  • 151.
    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. 

  • 152.
    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.

  • 153.
    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, Gothenburg, Sweden.
    Links between subjective assessments and objective metrics for steering, and evaluation of driver ratings2014Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 52, s. 31-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During the development of new vehicles, finding correlation links between subjective assessments (SA) and objective metrics (OM) is an important part of the vehicle evaluation process. Studying different correlation links is important in that the knowledge gained can be used at the front end of development, during testing and when creating new systems. Both SA from expert drivers using a rating scale of 1-10 and OM from different tests measured by a steering robot were collected using standard testing protocols at an automotive manufacturer. The driver ratings were evaluated and the correlations were analysed using regression analysis and neural networks through a case study approach. Links were identified and were compared with related research.

  • 154.
    Olofsson, Oscar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Investigation of Accuracy in Fuel Economy Measurement Methods2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Bakgrunden till det här examensarbetet är den ökade relevansen av att minska fordons bränsleförbrukning på grund av faktorer så som minskade oljeresurser och ökande bränslepriser. Tidigare utförda tester har visat att verklig bränsleekonomi skiljer sig nämnvärt från bränsleekonomi uppmätt med hjälp av simulerad vägkorsning i chassidynamometer. I det här arbetet undersöks noggranhet och repeterbarhet för olika mätmetoder som ofta används vid bränsleförbrukningsmätningar. Detta görs genom en teoretisk undersökning av noggrannheten för tillgänglig mätutrustning och en testserie med gradvis ¨okad komplexitet bestående av tester på chassidynamometer och väg. Testerna utförs med en Scania G450 lastbil som utrustats med en portabel bränsleflödesmätare och portabel avgasanalysator (PEMS). Variabler såsom temperaturer, motor-mod och vridmoment upptaget av olika externa aggregat analyseras för att ¨oka förståelsen för hur fordonets tillstånd skiljer sig mellan olika korningar. Vidare undersöks möjligheter inom sensorfusion för förbättring av mätnoggrannheten. Erhållna resultat visar att mätnoggrannheten för de olika utrustningarna ¨ar av storleksordningen 1 % vid vägkorsning men betydligt bättre vid körning i chassi-dynamometer. Det kan konstateras att ¨andringar av interna motorförluster påverkar bränsleekonomin i stor utsträckning även i kontrollerade testmiljöer. Slutligen kan det fastställas att bränsleflödesmätaren och den fordonsinterna bränsleförbrukning-uppskattningen reagerar likvärdigt på ändringar i bränsleförbrukning, medan den på avgasanalys baserade metoden reagerar annorlunda.

  • 155.
    Olsson, Magnus
    et al.
    SP Technical Research Institute of Sweden.
    Nybacka, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Blinge, Magnus
    Chalmers University of Technology.
    Nationell kraftsamling Transport 20502013Annet (Annet (populærvitenskap, debatt, mm))
  • 156.
    Oscarsson, Michael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    A Hydropneumatic Suspension Parameter Study on Heavy Multi-Axle Vehicle Handling2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The Swedish company Strömsholmen AB, which develops and manufactures gas springs for the tool and die industry, have entered the market of heavy duty off-road vehicles where they advertise their hydropneumatic suspension system. One of their customers is the Finnish defense company Patria, which produces the eight-wheeled military vehicle Patria AMV. In order to produce a more optimized suspension system for Patria, Strömsholmen is in need of learning more about how the vehicle dynamic properties such as handling are influenced by the suspension settings. To achieve this knowledge Strömsholmen started a collaboration with the consultant company FS Dynamics and initiated this master thesis work. The aim with this master thesis is to produce a simulation model of Patria AMV and investigate the influence of the suspension system settings on vehicle dynamic properties such as handling. The thesis work has resulted in a vehicle model in Adams/Car that is verified against experimental data from two slalom maneuvers. The model shows a good correlation with the validation data, taking into account the many assumptions and estimations that had to be made during the work due to lack of vehicle parameter data. A suspension parameter study was performed investigating vehicle maneuvers such as steady-state cornering and single-lane change. The results are summarized in a lookup table which can be used during future vehicle tests. Recommendations for future work is to verify some of the estimated vehicle parameters in the vehicle model as well as correlate test drivers subjective feel of the vehicle response to the calculated objective handling measures in this work.

  • 157. Pavasson, Jonas
    et al.
    Cronholm, Kent
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Strand, Henrik
    Karlberg, Magnus
    Reliability Prediction Based on Variation Mode and Effect Analysis2013Inngår i: Quality and Reliability Engineering International, ISSN 0748-8017, E-ISSN 1099-1638, Vol. 29, nr 5, s. 699-708Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The possibility of predicting the reliability of hardware for both components and systems is important in engineering design. Today, there are several methods for predicting the reliability of hardware systems and for identifying the causes of failure and failure modes, for example, fault tree analysis and failure mode and effect analysis. Many failures are caused by variations resulting in a substantial effect on safety or functional requirements. To identify, to assess and to manage unwanted sources of variation, a method called probabilistic variation mode and effect analysis (VMEA) has been developed. With a prescribed reliability, VMEA can be used to derive safety factors in different applications. However, there are few reports on how to derive the reliability based on probabilistic VMEA, especially for transmission clutch shafts. Hence, the objective of this article was to show how to derive system reliability based on probabilistic VMEA. In particular, wheel loader automatic transmission clutch shaft reliability is investigated to show how different sources of variation affect reliability. In this article, a new method for predicting system reliability based on probabilistic VMEA is proposed. The method is further verified by a case study on a clutch shaft. It is shown that the reliability of the clutch shaft was close to 1.0 and that the most significant variation contribution was due to mean radius of the friction surface and friction of the disc.

  • 158.
    Peluchon, Mathias
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Autonomous landing of multicopters on mobile platforms: Design of an autonomous landing solution for multicopters on mobile platforms, based on a ultrasonic local positionning technology2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This work studies the use of an ultrasonic 3D positioning system in multicopter landing applications. Its aim is to develop a solution for autonomous landing of rotary wings systems on mobile platforms, especially boat decks using the positioning system developed by the French startup Internest. First, the position sensing algorithms will be improved so as to let them provide accurate relative position measurements in moving reference frames. Then a first implementation of a control algorithm based on PIDs will be considered, discussed and tested. Finally some improvements will be studied, with the use of trajectory planning and feedforward control, as well as the definition of a reference model. The whole work is led in an industrial R&D context, with the aim of developing simple but effective solutions that can easily be used in numerous applications, on a large variety of systems.

  • 159.
    Perinciolo, Paolo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Sondhi, Eshwar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Model Based HandlingAnalyses2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The thesis consists of building vehicle models for lateral dynamics that provide accurate results, while being simple enough to highlight clear relationships between vehicle properties and handling behaviours. The approach that characterizes the present work is built on the foundations provided by the bicycle, or single-track, model (STM). Nonetheless, its developments and improvements substantially differ from the usual sequence found in literature. Most studies based on this analytical vehicle model satisfy the quest for increased robustness by involving nonlinear description of the contact forces generated between tyres and ground.

    The presented analysis, instead, embraces the challenge of using completely linear models to describe vehicle lateral dynamics in a variety of driving situations. Hence, the aim of this thesis is to provide the reader with a deeper understanding of the effects of various physical properties on the actual dynamic behaviour, by complementing numerical correlations obtained from simulation outputs with analytical descriptions of their causes. The first step of the presented work deals with the selection and design of driving scenarios aiming at comprehensively evaluating vehicle handling, as well as defining the boundaries of the investigation. As in most engineering problems, a compromise has to be sought, since the set of maneuvers has to be broad enough to point out various dynamic characteristics, while limiting the time needed to perform evaluation of a real vehicle. Furthermore, the space occupation of each maneuver must allow execution in an actual testing facility. The design of suitable driving scenarios triggers an iterative process, in which the initial formulation of the single-track model is complemented with additional states and sources of complexity, based on the limitations that simulation outcomes point out. A complex model, previously built with the aid of Multi-Body Dynamics software, is initially accepted as a \black box", and adopted as a reference to estimate qualities and deficiencies of the results. The next step of the work deals with physical vehicle testing and correlation. After post-processing the data and comparing it to the analytical vehicle model, it is seen that the vehicle model represents the physical vehicle behaviour very well. The area where the model lacks is in transients, which in-turn can be explained by the lack of compliance in the system. The last part of the thesis brie y touches upon the vehicle behaviour in a dynamic driving simulator along with effects of motion cueing gains.

  • 160.
    Poiret, Simon
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Development of a simulation tool for dynamic behaviour of cross country rally cars2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This study was conducted for the cross-country rallying department of Peugeot Sport in 2016. The goal was to develop vehicle dynamic simulation processes and exploit them in order to speed up the suspension development on the DKR buggy. After careful analysis of the various solutions available (both in terms of physics and softwares), the option of a full vehicle model developed on the VI-Motorsport suite was favored. In order to setup this model correctly, the required vehicle data were measured and integrated. Certain elements required a thorough study and specific measurements to be properly modeled, including the tires and the dampers. Specific correlation testing was also performed to refine the modeling later on. Finally, the model was used to investigate new damper laws and compare them. 156 theoretical laws were created and evaluated on 3 road profiles identified as relevant and representative for the cross-country rallying program. The outcomes of this study were then integrated in the design of new dampers to be tested on track. The simulation tool developed during this project will be able to reveal several interesting development paths both in terms of kinematics and dynamics of the buggy’s suspension.

  • 161.
    Qiu, Jie
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Study of driver models forside wind disturbances2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    As the development of highways, it is quite normal for buses running in a speed around

    100km/h. When buses are running in a high speed, they may suffer from the influence of side

    wind disturbances at anytime. Sometimes, it may result in traffic accidents. Therefore, the

    study of bus stability under side wind disturbances becomes more and more important. Due to

    restrictions of real tests, computer simulation can be used to study this subject. The bus side

    wind response character is reflected through the driver’s manoeuvre , so open-loop analysis is

    hard to give a comprehensive evaluation of the side wind stability of the bus. Therefore,

    closed-loop analysis is studied in this thesis.

    An ADAMS bus model and a side wind force model are developed in this thesis, along with

    two driver models, the PID control model and the preview curvature model. The driver

    models are built in Simulink and co-simulation between ADAMS/View and Simulink is

    conducted.

    The results of co-simulation show that the two driver models can both control the bus from

    deviating from the desired course under side wind disturbances. The PID control model is

    simple and shows a very good control effect. The maximum lateral displacement of the bus by

    PID control model is just 0.0205m under maximum side wind load 1000N and 2500Nm when

    preview time is 1.2s, while it is 0.0702m by preview curvature model, however, it is difficult

    to determine the coefficients Kd, Kp, and Ki in the PID controller. The preview curvature

    model also shows a good control effect in terms of the maximum lateral displacement and

    yaw angle of the bus. Comparing these two models, the PID control model is more sensitive

    to deviations, with quicker response and larger steering input.

    The bus model system is stable under side wind disturbances. Through driver ’s proper steering manoeuvre, the bus is well controlled. The closed-loop analysis is a good method to study the bus stability under side wind disturbances.

  • 162.
    Quezada, Felipe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    De Freitas Martínez, Andrés
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Magnetsvävartåg, något för framtiden?: En jämförelse mellan magnetsvävartåg och höghastighetståg på järnväg2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Populationen i de stora städerna växer mer och mer. Det skattas att drygt 60 % avvärldens befolkning ska flytta till stora städer om två årtionden och av denna anledningbehövs det nya lösningar och alternativ till dagens transportsystem. En åtgärd sommånga industrialiserade länder använder är att implementera höghastighetståg påjärnvägståg där konventionella järnvägståg täcker transportbehovet. Men vad skullehända om magnetsvävartåg skulle implementeras istället?

    Syftet med detta arbete är att få en uppskattning om magnetsvävartåg kan vara en bättrelösning än höghastighetståg på järnväg. För att möjliggöra detta analyseradesmodellerna Shinkansen N700A och ICE3 inom järnväg samt Transrapid TR09 ochSCMaglev MLX01 inom magnetssvävning. Aspekterna som säkerhet,energiförbrukning, miljöpåverkan och kostnad för alla fyra modellerna undersöktes.

    Angående säkerhet kunde man konstatera att båda systemen håller en högsäkerhetsstandard men båda har varit inblandade i olyckor, vilket på sätt och vis är braför att de alltid medför nya säkerhetsåtgärder för att göra systemet ännu säkrare ochinnebär att båda system inte kan garantera att ingen kollision eller urspårning sker. Närdet gäller energiförbrukningen blev resultatet att både TR09 och ICE3 förbrukar sammaenergi vid maximal tillåten hastighet samt att Shinkansen N700A förbrukar betydligtmindre än MLX01. Med tanke på att energiförbrukningen är proportionell motkoldioxidemissioner följer att N700A bidrar mindre till koldioxidemissioner än MLX01samt att både TR09 och ICE3 bidrar lika mycket.

    Ingen av dessa tre aspekter var avgörande för att visa att ett system var lönsammare ändet andra, men hur stor skillnad blev det på kostnadsdelen? Resultatet visade attkostnader på infrastrukturen för magnetsvävartåg var mycket större än för järnvägståg.Å andra sidan har ett land som Tyskland (pionjärer inom magnetsvävartekniken) lagtner sina projekt om att bygga ett nytt magnetsvävartåg. När det gäller driftskostnadernaför höghastighetstågen så var det ingen avsevärd skillnad mellan tågsystemen. Förfordonskostnader kunde man inte någon komplett bild ges, på grund av brist påkostnadsinformation med avseende på japanska SCMaglev MLX01. Men med avseendepå övriga tre system så var japanska järnvägståget Shinkansen N700A dyrast med enkostnad på $44 miljoner per enhet, följt av Tyska Transrapid TR-08 med enfordonskostnads på $12.9 miljoner per vagn och billigast är ICE3 tåget som kostar $3.7miljoner per fordon.

    Med tanke på all information och data som samlades data drogs slutsatsen att det inte ärlönsamt att bygga ett magnetsvävartåg, inte med den teknik som finns idag. Omtekniken utvecklas vidare så att infrastrukturkostnaderna minskas avsevärt kan docksystemet vara en bra lösning för framtiden.

  • 163.
    Ramachandra, Rakshith
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Ammonia Dosing Control Strategy for heavy duty automotive SCR2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Selective Catalytic Reduction (SCR) has proven to be the frontrunner for the removal of nitrogen oxides (NOX) from exhaust gas. EURO VI emission regulations present a challenge from the control point of view, so as to achieve high NOX conversion while keeping the ammonia slip under control. This thesis focuses on a model based feedforward control system to dose the urea. The SCR is modeled as a series of CSTR (continuously stirred tank reactor) with the main SCR chemical kinetics. The main reactions are ammonia adsorption, desorption, fast SCR, slow SCR, standard SCR and ammonia oxidation. The model is simplied so as to capture the important dynamics and be fast at the same time. A fast and computationally less demanding model is required from a control aspect if it has to be implemented online.

    Two control strategies were evaluated. The rst control strategy maintains a constant ammonia slip whereas the second controller maintains a constant NOX to ammonia ratio at the outlet of the SCR. The catalyst used is an extruded vanadia based catalyst. The control strategy was tested on the engine bench with a 11.4L catalyst and an inline 6 cylinder 12.8L engine. The performance of the controller was very good compared to a at urea dosing. The control strategy achieves a higher NOX conversion, less ammonia slip and uses less urea for injection.

  • 164.
    Rehnberg, Adam
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Suspension design for off-road construction machines2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Construction machines, also referred to as engineering vehicles or earth movers, are used in a variety of tasks related to infrastructure development and material handling. While modern construction machines represent a high level of sophistication in several areas, their suspension systems are generally rudimentary or even nonexistent. This leads to unacceptably high vibration levels for the operator, particularly when considering front loaders and dump trucks, which regularly traverse longer distances at reasonably high velocities. To meet future demands on operator comfort and high speed capacity, more refined wheel suspensions will have to be developed. The aim of this thesis is therefore to investigate which factors need to be considered in the fundamental design of suspension systems for wheeled construction machines.

    The ride dynamics of wheeled construction machines are affected by a number of particular properties specific to this type of vehicle. The pitch inertia is typically high in relation to the mass and wheelbase, which leads to pronounced pitching. The axle loads differ considerably between the loaded and the unloaded condition, necessitating ride height control, and hence the suspension properties may be altered as the vehicle is loaded. Furthermore, the low vertical stiffness of off-road tyres means that changes in the tyre properties will have a large impact on the dynamics of the suspended mass. The impact of these factors has been investigated using analytical models and parameters for a typical wheel loader. Multibody dynamic simulations have also been used to study the effects of suspended axles on the vehicle ride vibrations in more detail. The simulation model has also been compared to measurements performed on a prototype wheel loader with suspended axles.

    For reasons of manoeuvrability and robustness, many construction machines use articulated frame steering. The dynamic behaviour of articulated vehicles has therefore been examined here, focusing on lateral instabilities in the form of “snaking” and “folding”. A multibody dynamics model has been used to investigate how suspended axles influence the snaking stability of an articulated wheel loader. A remote-controlled, articulated test vehicle in model-scale has also been developed to enable safe and inexpensive practical experiments. The test vehicle is used to study the influence of several vehicle parameters on snaking stability, including suspension, drive configuration and mass distribution. Comparisons are also made with predictions using a simplified linear model.

    Off-road tyres represent a further complication of construction machine dynamics, since the tyres’ behaviour is typically highly nonlinear and difficult to evaluate in testing due to the size of the tyres. A rolling test rig for large tyres has here been evaluated, showing that the test rig is capable of producing useful data for validating tyre simulation models of varying complexity.

    The theoretical and experimental studies presented in this thesis contribute to the deeper understanding of a number of aspects of the dynamic behaviour of construction machines. This work therefore provides a basis for the continued development of wheel suspensions for such vehicles.

  • 165.
    Rehnberg, Adam
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Vehicle dynamic analysis of wheel loaders with suspended axles2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The wheel loader is a type of engineering vehicle used primarily to move crude material over shorter distances. As the vehicle is designed without wheel suspension, wheel loader drivers are exposed to high levels of whole body vibration which influences ride comfort negatively. The work presented in this thesis has the aim to investigate the potential in adding an axle suspension to a wheel loader in order to reduce vibrations and increase handling quality. While suspended axles have great potential for improving ride comfort and performance, they will also necessarily affect the vehicle dynamic behaviour which is different in many aspects from that of passenger cars or other road vehicles: the wheel loader has a large pitch inertia compared to its mass, the axle loads vary considerably with loading condition, and the vehicle uses an articulated frame steering system rather than wheel steering. These issues must all be considered in the design process for a wheel loader suspension.

    The effects of suspended axles on ride vibrations are analysed by simulating a multibody wheel loader model with and without axle suspension. Results from the simulations show that longitudinal and vertical acceleration levels are greatly reduced with axle suspension, but that the decrease in lateral acceleration is smaller. By reducing the roll stiffness lateral accelerations can be further reduced, although this may not be feasible because of requirements on handling stability. The pitching oscillation of the vehicle has also been studied as this is known to have a large influence on ride comfort. An analytical model is used to study the effect of front and rear suspension characteristics on the pitching response of the wheel loader, showing that a stiffer rear suspension is favourable for reducing pitching but also that a similar effect is attainable with a stiffer front suspension. Results are compared to multibody simulations which show the same trend as analytical predictions. By including a linearised representation of a hydropneumatic suspension in the models, it is also shown that favourable dynamic behaviour can be maintained when the vehicle is loaded by utilising the fact that suspension stiffness is increasing with axle load.

    Articulated vehicles may exhibit lateral oscillations known as "snaking" when driven at high speed. The effect of suspended axles on these oscillations are analysed using a multibody simulation model of a wheel loader with an equivalent roll stiffness suspension model. It is found that the roll motion of the sprung mass has a slightly destabilising effect on the snaking oscillations. This effect is more pronounced if the body roll frequency is close to the frequency of the snaking motion, although this loss in stability can be compensated for by increasing the equivalent stiffness or damping of the steering system.

    Together with existing vehicle dynamic theory and design rules, the studies reported in this work provide an insight into the specific issues related to suspension design for wheel loaders.

  • 166.
    Rehnberg, Adam
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Influence of tyre properties on the ride dynamics of heavy off-road vehicles2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Wheeled earthmoving machines are a class of off-road vehicles that are typically equipped withlarge and soft tyres to obtain sufficient traction and flotation on unpaved surfaces. Theunsuspended mass is typically larger than for road vehicles. This indicates that the tyreproperties will affect not only the dynamics of the wheels and axles, but may also have asubstantial effect on the ride dynamics of the vehicle. This paper investigates how the tyrecharacteristics influence the optimal design of a wheel suspension for an off-road constructionmachine. Frequency domain analysis of a pitch and bounce model show that overallacceleration levels are significantly affected by tyre stiffness and damping, but that the tradeoffbetween pitch and bounce is unaffected by tyre properties although the main ride frequenciesare offset. Also, optimal suspension damping is fairly independent of the tyres. It is alsoinvestigated if a locked front axle suspension may be used in the loaded case, to simplifysuspension system design by using tyres as sole suspension elements. It is found that thisconfiguration leads to decreased ride quality, mainly due to the increased suspension stiffnessand lack of damping.

  • 167.
    Rehnberg, Adam
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Pitch comfort optimisation of a front end loader using a hydropneumatic suspension2007Inngår i: SAE technical paper series, ISSN 0148-7191, nr 2146, s. 67-76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Front end loader vehicles are prone to excessive pitching when travelling at high speed, partly due to the absence of axle suspension. This paper studies the fundamental design of a hydropneumatic suspension for a medium wheel loader. The vehicle is analysed using an analytical frequency response model as well as multibody simulations. Results show that favourable pitching response can be achieved by increasing the rear axle stiffness, but also that a similar effect is achieved with higher front axle stiffness. For the loaded vehicle, it is also found that the benefits of an optimal stiffness distribution are offset to some extent by the reduction in relative damping as the vehicle mass and inertia increases. Thus, it is desirable to increase suspension damping under load to maintain a suitable level of relative damping.

  • 168.
    Rehnberg, Adam
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Ride comfort simulation of a wheel loader with suspended axles2008Inngår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 3, nr 3, s. 168-188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wheel loaders are used in a variety of tasks. The traditional design of the vehicle is unfavourable from a ride comfort standpoint, as the unsuspended axles lead to high vibration levels. This study investigates the possibility to reduce driver vibrations by introducing suspended wheel axles. A multibody simulation model is used to study vibration levels with and without suspension. Results show that vertical and longitudinal vibrations are reduced significantly when comparing with the unsuspended vehicle. Less reduction is attained in the lateral direction, mainly because of high roll stiffness and the high placement of the driver seat.

  • 169.
    Rehnberg, Adam
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Snaking stability of articulated frame steer vehicles with axle suspension2010Inngår i: International Journal of Heavy Vehicle Systems, ISSN 1744-232X, Vol. 17, nr 2, s. 119-138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A known problem of articulated vehicles is that snaking oscillations may occur at high speed. For ride comfort reasons, it is desirable to introduce suspended axles on articulated vehicles such as wheel loaders which are traditionally built without wheel suspension. This paper investigates how this may affect the snaking stability, by studying the vehicle dynamic behaviour of a multibody simulation model with and without suspension. Results show that an axle suspension may have a slightly destabilising effect, although the difference is small and can be offset by a stiffer or more damped steering system.

  • 170.
    Rehnberg, Adam
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Edrén, Johannes
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Eriksson, Magnus
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Scale model investigation of the snaking and folding stability of an articulated frame steer vehicle2011Inngår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 6, nr 2, s. 126-144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the development and evaluation of an articulated frame steer testvehicle on a model-scale. Vehicles with articulated steering are known to exhibit unstable behaviour in the form of snaking or folding instabilities when operated at high speed, as previously studied using analytical models, simulations and full vehicle tests. The aim ofthis study is to design a scaled test vehicle that is able to reproduce unstable modes found in articulated vehicles. The model vehicle may provide greater insight than simulations, while avoiding the costs and hazards associated with full vehicle tests. The objective is also to investigate how well a linearised planar model and eigenvalue analysis can predict vehicle stability properties. Experimental and theoretical results have been critically analysed, and found to exhibit typical full vehicle behaviour. The linear mathematical model exhibited similar trends when compared to the scale model test results.

  • 171.
    Rothhämel, Malte
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Capturing steering feel: a step towards implementation of active steering in heavy vehicles2010Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 172.
    Rothhämel, Malte
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Characterisation and Utilisation of Steering Feel in Heavy Trucks2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Steering is next to braking the most important control feature of a road vehicle. The driver gives input through the steering wheel and the vehicle reacts in a certain way, which results in a transfer function between input and output. The transfer function can be modified by means of an actuator in the steering system to improve safety, handling and steering feel. To be able to use active steering systems to improve the steering feel, we need to understand how steering feel comes about. There have been several investigations to find out how drivers experience a change in vehicle steering and handling behaviour and how a change in vehicle handling behaviour affects the driver. However, as yet, there is no standardised way to find mutual corresponding measurements, assessments and ratings, nor is there a consistent definition of steering feel. An important part of investigating steering feel concerns how to measure what drivers feel. One of the essential prerequisites in the present research work is that steering feel, as perceived by human beings, can be allotted in dimensions. To define this non-instrumental space, a method to find the dimensions that people use to perceive and describe steering feel has been developed. It is shown that it is possible to extract up to nine dimensions describing the steering feel of road vehicles. This was experimentally evaluated using a driving simulator. In the test, drivers assessed truck steering system settings that differed in friction, damping, inertia and stiffness, due to five dimensions of steering feel. The same steering system settings were also tested in accordance with ISO standards for vehicle handling to acquire characteristic instrumental quantities. The instrumental measurements and the non-instrumental assessments were then analysed with respect to their correlation with each other. The results show that there are indeed correlations and also which of the handling quantities influence which dimension of steering feel.One possible use of the increased knowledge of steering feel evaluation is to influence the driver's behaviour by a directed change of steering feel. In a track test the steering wheel torque of a truck was modified depending on the lateral dynamic vehicle driving state. During the experiment the cornering behaviour of truck drivers was evaluated regarding lateral acceleration, which is related to rollover accidents. Statistical evaluation showed a decrease of maximum lateral acceleration values while cornering when the steering wheel torque was decreased at high lateral acceleration. There are also more possibilities to modify the transfer function between driver input and vehicle response. Artificial understeering and yaw rate gain acceleration are two functionalities that were developed during this work and were evaluated by simulation. Thus, based on the knowledge about steering feel, an application-oriented hypothesis could be formulated and evaluated. The fundamental part of this thesis contributed a puzzle piece to the mapping of steering feel while the advanced part established ties to future applications with active and semi-active steering as well as driver assistance systems.

  • 173.
    Rothhämel, Malte
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Fail-operational vehicle dynamics for autonomous operation—A review through other engineering domains2018Inngår i: The Dynamics of Vehicles on Roads and Tracks, CRC Press/Balkema , 2018, s. 491-496Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For vehicles in autonomous operation, fail-operational chassis components will be needed. ISO 26262 gives guidelines on how to proceed in the development process, however, it does not provide technical solutions. Anyhow, there are fail-operational systems realized in other domains from which to get inspiration. Agriculture, railway, aviation and naval systems are shown here as examples. Experience shows that an overview of rules and standards and approaches in other domains opens our eyes for practical solutions.

  • 174.
    Rothhämel, Malte
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    IJkema, Jolle
    Scania AB.
    Finding correlation between handling values and the drivers’ performance using a moving base driving simulator2011Inngår i: Proceedings of the 22st International Symposium: Dynamics of Vehicles on Roads and Tracks, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work presents the evaluation of an experiment on the relationship between driver performance and vehicle handling quantities. Both of them are instrumental quantities, however, the former are driver dependent, the latter are only vehicle dependent. A moving base driving simulator was used to examine 16 truck-trailer-combinations. The driving of 28 test drivers in a special developed manoeuvre resulted in characteristic driver performance values evaluated of vehicle system quantities measured while driving. Stationary and dynamical ISO-handling tests resulted in handling quantities. The correlation by means of regression analysis between these driver performance values and the quantities of the ISO-handling tests are presented here as a step towards the mapping of steering feel.

  • 175.
    Rothhämel, Malte
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    IJkema, Jolle
    Scania CV AB.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    A method to find correlations between steering feel and vehicle handling properties using a moving base driving simulator2011Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 49, nr 12, s. 1837-1854Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There have been several investigations to find out how drivers experience a change in vehicle-handling behaviour. However, the hypothesis that there is a correlation between what the driver perceives and vehicle-handling properties remains to be verified. To define what people feel, the human feeling of steering systems was divided into dimensions of perception. Then 28 test drivers rated different steering system characteristics of a semi-trailer tractor combination in a moving base-driving simulator. Characteristics of the steering system differed in friction, damping, inertia and stiffness. The same steering system characteristics were also tested in accordance with international standards of vehicle-handling tests resulting in characteristic quantities. The instrumental measurements and the non-instrumental ratings were analysed with respect to correlation between each other with the help of regression analysis and neural networks. Results show that there are correlations between measurements and ratings. Moreover, it is shown that which one of the handling variables influence the different dimensions of the steering feel.

  • 176.
    Rothhämel, Malte
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Ijkema, Jolle
    Scania.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Artificial understeer by means of active steering: an investigation of proper handling test methods2013Inngår i: Proceedings of the 23rd Symposium of the International Association for Vehicle System Dynamics, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper shows for a heavy truck simulation model the advantages of an artificial understeering functionality realised by a PID controlled active front steering system based on linear calculated yaw rate error. The yaw rate error results from the difference between measured vehicle yaw rate and a linear calculated yaw rate based on steering wheel angle and vehicle speed. The integrated controlled system shows increased performances: The more linear-like behaviour together with a higher understeer gradient over a wide lateral acceleration range which increases safety especially in emergency conditions.

  • 177.
    Rothhämel, Malte
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    IJkema, Jolle
    Scania AB.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Finding correlation between steering feel assessments and the driver’s performance using a moving base driving simulator2011Inngår i: FAST-zero’11, Society of Automotive Engineers, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    There is not yet a standardised method to find mutual corresponding subjective and objective measurements. This paper describes how non-instrumental measurements (made by human measurement gauges) and instrumental measurements (made by measuring instruments) can be distinguished in quantities that are dependent of the vehicle, the driver's skills or the driver's individual preferences. Moreover, this paper shows the correlation between instrumental and non-instrumental measurements.

  • 178.
    Rothhämel, Malte
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Ijkema, Jolle
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Influencing driver chosen cornering speed by means of modified steering feel2014Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 52, nr 4, s. 522-538Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents an investigation about influencing the driver's behaviour intuitively by means of modified steering feel. For a rollover indication through haptic feedback a model was developed and tested that returned a warning to the driver about too high vehicle speed. This was realised by modifying the experienced steering wheel torque as a function of the lateral acceleration. The hypothesis for this work was that drivers of heavy vehicles will perform with more margin of safety to the rollover threshold if the steering feel is altered by means of decreased or additionally increased steering wheel torque at high lateral acceleration. Therefore, the model was implemented in a test truck with active steering with torque overlay and used for a track test. Thirty-three drivers took part in the investigation that showed, depending on the parameter setting, a significant decrease of lateral acceleration while cornering.

  • 179.
    Rothhämel, Malte
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    IJkema, Jolle
    Scania CV AB.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    On a Method for Generating a Word Pool for the Description of Steering Feel2010Inngår i: AVEC 10 - Proceedings, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    “If touching is not a single perception but a plural, then its objects are a plurality, too.” (Aristotle)

    For investigating steering feel, a very important part is how to measure what people feel. The hypothesis in the present research work is that steering feel, as perceived by human beings, can be allotted in dimensions. The steering feel of a certain vehicle can then be seen as a point in a space with multiple orthogonal dimensions. The aim is to find the dimensions that people use to perceive and describe steering feel, in order to define this non-instrumental space. This article describes two modes of evaluation, a manual mode anda mathematical mode using the statistical method of multidimensional scaling. Applying these modes, it has been possible to extract nine dimensions describing the steering feel of road vehicles.

  • 180.
    Rothhämel, Malte
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    IJkema, Jolle
    Scania CV AB.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    On the correlation between steering feel and handling in heavy trucks2008Inngår i: FISITA World Automotive Congress 2008, Congress Proceedings - Mobility Concepts, Man Machine Interface, Process Challenges, Virtual Reality: Volume 1, 2008, s. 311-317Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Driving a car gives us a certain feeling. Driving another car returns a very differentexperience. If we could drive with closed eyes, we could nonetheless explain which vehicle itwas we were sitting in. Not only are there differences between sports cars and transporters orlimousines and trucks, but also it is possible to feel the different sensations from drivingtrucks of different manufacturers. It depends on the seat, the sitting position, the view, thesound, the performance, the brakes - and the steering feel.There are many ways how to describe a vehicle's steering feel. There are ISO-standards, suchas ISO/TS 20119 and ISO 14792 that generate characteristic values, there are subjective testsof automotive magazines, and there are opinions of test and race drivers. But exactly there,between the pure objective tests and the subjective impressions that are difficult to describe,exists a gap. This relationship between instrumentally measured numbers and nearlyindescribable feelings has not been fully investigated yet. With a better understanding of thecorrelation between objective values and subjective experience, it may be possible to find ananswer on which parameters can manipulate the feelings.This paper is on an investigation about finding a correlation between instrumental values(values measured by instruments or calculated from those) and non-instrumental values(values obtained by human impressions). The idea is to use drivers as human measuringgauges and let them measure impressions in their own words.Thus, in order to gather a standardized answer that can be evaluated, a questionnaire wasdeveloped. For this questionnaire the most important consideration was to facilitate the testdrivers with their own languages. Therefore, the questions were developed in the test drivers'native language. The characteristic words were chosen corresponding to the results of adouble interrogation process.When people express their feelings like they are accustomed to do, they will utilize a libraryof expressive words instead of numbers. Thus the measuring results will have that character,too. By using the semantic differential method, expressions can be translated into numbers.The semantic differential method is a well-known method especially in psychoacousticswhich allows people describe how noise sounds to them. With this kind of evaluation - valueassigning procedure - a list of parameters comes to existence similar to that containing theinstrumental values. To explore the relation between the instrumental and non-instrumentalvalues, statistical methods are used.

  • 181.
    Salminen, Henry
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Parametrizing tyre wear using a brush tyre model2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Studying rubber wear is important because it can save money, minimize health and environmental issues related to the particles generated from tyre wear and reduce fuel consumption. The wear of rubber is considered to be the result of energy dissipation due to friction. There are many models that describe the dynamical behaviour of vehicles and tyre, but less e ort has been dedicated to consider the tyre wear in these models.

    The purpose of the thesis was to create an easy to understand and trend-accurate tyre wear model for implementation in a complete car model. The tyre wear in the thesis is determined to be the amount of rubber volume loss due to sliding per unit length that the tyre travels. A literature study was performed with the objective of gaining knowledge of tyre models and the a ecting parameters of tyre wear. The most important parameters in determining tyre wear were identied as the forward velocity, side-slip angle, longitudinal slip, vertical load, and tyre ination pressure. The wear was chosen to be calculated with Archards wear law for these parameters both separately and combined in pairs in order to obtain a deeper understanding of the wear.

    The results show that wear is increasing exponentially for the forward velocity. Tyre wear decreases linearly as tyre ination pressure (vertical bristle sti ness) increases. The vertical load, longitudinal slip and side-slip angle yielded exponentially increasing wear. The most inuential parameters a ecting the tyre wear were the longitudinal slip and side-slip angle, these yielded wear rates up to 107 higher compared with the reference case.

    The developed tyre wear model is a good base for future work. More measurement data are needed in order to validate the model. For future work it is also recommended to implement camber angle and temperature dependency in order to study these two important parameters inuence on tyre wear.

  • 182.
    Sarmah, Biki
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Optimisation of Electromechanical Drivetrain for Wave Energy Converter at CorPower Ocean AB2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The potential of wave energy has been constantly explored in past couple of years. The contribution from the CorPower Ocean AB towards the development of wave energy is important. This thesis involves the detailed study of current ½ scale (1:2) model of a Wave Energy converter (WEC) and computing the results to find the optimised component ratings. The primary goal of the thesis is to optimise each component of the electro-mechanical drivetrain with the assistance of modelling software Simulink and Matlab. In the initial stage of this thesis the generator and drive component are analysed without changing the drivetrain configuration of the WEC. A method is established to find suitable ratings of generator and drive system for the WEC which provides high system efficiency and power output. The method is developed in such a way that it can be implemented for any scale model whether it is full-scale or half-scale. Once finding the optimised ratings of generator and drive combination, different configuration of the drivetrain is explored for the WEC. The influence of drivetrain mechanism with and without flywheel is also considered and compared with the ½ scale model. The drivetrain configurations comprise of single generator, double generator and quadruple generator alignment with the WEC.  All configurations of the generator are compared with and without a flywheel in the drivetrain. The benefit of including a flywheel involves power smoothing, control simplification and reducing component volume, whereas the benefit of not including flywheel includes better hydrodynamic damping and control. The outcome of the results showcase that the existing ½ scale WEC model can provide better performance when the generator ratings are reduced because of low speed at small sea state. The speed-ratio of the gearbox can either be increased or a new system can be introduced which chooses the generator rating depending on the sea state and motion profile. Based on the analysis result of an optimised ½ scale model, the full scale drivetrain component ratings are introduced with a different drivetrain topology. Results from the Full scale WEC model showcase that a double generator WEC configuration without a flywheel is a reliable and efficient solution for CorPower Ocean AB.

  • 183.
    Sedin, John
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Optimization of Extreme Environment Cyclic Testing: Analysis of thermal cycle load cases on a plastic cab component through simulation and testing2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this Master thesis was to deepen the knowledge and understanding regarding control parameters for the Extreme Environment Cyclic Testing (EECT) on interior and exterior cab components. The investigated parameters were temperature gradient, length of the warm and cold sections and number of cycles. These parameters were investigated since they control the settings of the Extreme Environment Cyclic Testing. In addition, temperature data was also gathered in order to be analysed along with a simplified case of sun radiation. The method consisted of three parts, where the first part was to perform a literature survey to gather relative data and knowledge. The second part was to perform simulations in COMSOL Multiphysics and the third part consisted of physical testing at Scania and at SP in Borås. To gather temperature data a simulation of a field test was performed in a wind tunnel at Scania.

    The results displayed a difference of the thermal image of the component when a simplified sun case was compared to a case without applied sun light. Regarding temperatures and temperature gradients it was found that a temperature gradient, based on testing from South Africa, can be up to 2.91°C/min in nature. The temperature results displayed a clear difference between obtained temperatures in a cab compared to results from a car. The angle of the windscreen and the volume difference are believed to be parts of the explanation. The simulations showed that an increase of the temperature gradient to 2°C/min from 1°C/min can be done without changing the time that the temperature of the material is heated respectively cooled significantly. These results were supported from the component testing at Scania which displayed that the difference in strain range when the temperature gradient was changed between 1°C/min to 2°C/min was below 1.2 %, which corresponds to less than 1E-4. The testing at Scania also displayed that the change in maximum strain for different length configurations, 3 h cold 6 h warm, 4 h cold 8 h warm and 6 h cold 12 h warm, could be neglected. The deviation in strain range between the 3h6h and 4h8h configuration was found to be below 1 %, which in absolute terms was 5E-5. It was also showed that the variance of the strain range did not change significant after six cycles.

    The maximum deviation in strain range between six and ten cycles was 0.15 %. The testing at SP with deformation scans with structural light scans displayed fluctuation in the deformation for the first cycles and a consistent decrease of maximum deformation after 8 cycles. The conclusions from the sun light simulations in COMSOL Multiphysics were that the difference between a simplified sun radiation case with a homogenous ambient temperature and the more realistic one with a set temperature on one surface of the component in combination with a homogenous ambient temperature could be neglected for components with a height up to 0.01 m. This was only valid if the temperature difference was below 10°C. For a larger temperature difference it was found valid for a height up to 0.001 m. Based on the results the author recommends that the control parameters of the Extreme Environment Cyclic Testing are set accordingly to obtain a more efficient testing method:  The number of cycles in the EECT should be 8, since more cycles will not make a significant change on the results

     The time should be 3 h in the cold section and 6 h in the warm section

     The increase of temperature should be 2°C/min to improve testing efficiency

    Also, an additional suggestion is to investigate the possibility of a pre-thermal heating phase in the EECT.

  • 184.
    Sedvallson, Robin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Automatic Classification of Traffic Situations using On-board Recorded Vehicle Data2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this Master’s thesis a method to automatically classify log files containing recorded vehicle data from Scania trucks is investigated.The files were recordings of data from the on-board controller area network(CAN)-buses and were gathered from field test vehicles during normal operating conditions. All the recordings were triggered by the embedded collision warning system. The test vehicles were equipped with a forward looking radar giving information about the surrounding traffic. Seven classes of traffic situations were proposed as classes to try to detect automatically. These classes were Queue, Vehicle ahead turns left,Vehicle ahead turns right, Roundabout, Catch up, Overtake and Overtakebicycle.Using Matlab, an evaluation tool was made to handle and analyse the log files. The tool converts the log files in all necessary steps in orderto analyse and classify the contents of each file. The results is presented in plots and also stored in a file for later review.To classify the files automatically, three methods have been tested and two of the methods have been used for this task. The first method uses a set of conditions on the signals to determine the class, the secondmethod uses a decision tree to differentiate the classes. A cluster analysisof the log files showed not to be an effective method of classifying thefiles and was therefore not fully developed.The result showed that the classification rules detected over 85%of the 192 available situations compared to the “decision tree”-methodwhich detected a maximum of 75% of the situations. The drawback ofthe first method was that the more correct detections also meant morefalse detections. The specificity was used as a measure of how well the method was able to leave the non-existing situations undetected. Thespecificity for the “classification rules”-method was approximately 85%and for the decision tree the specificity was approximately 95%.The conclusion is that both the “classification rules”- and the “decisiontree”-method can be used to classify the log files, however thefirst method produces more detections but less specific, and vice versafor the latter. The methods can be further developed using more of theavailable signals or by working with the specific conditions used by themethods.

  • 185.
    Sengupta, Abhinav
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Gurov, Alexey
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Evaluating the effectiveness of collisionavoidance functions using state-of-the-artsimulation tools for vehicle dynamics2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main goal of this work is to gain knowledge of how and to what extent state-of-the-artsimulation tools can be used in a conceptual development phase for vehicle dynamics control atVolvo Car Corporation (VCC).The first part of the thesis deals with an evaluation of vehicle dynamics simulation tools and theiruses. The three simulation tools selected for the study, namely Mechanical Simulation CarSim 8.2.1,IPG CarMaker 4.0.5, and VI-Grade CarRealTime V14, are briefly described and discussed. In order toevaluate and compare these tools with respect to application for vehicle dynamics control, a criterialist is developed covering aspects such as tool requirements and intended usage. Based on thecriteria list and certain identified drawbacks, a ranking of the tools is made possible. Furthermore,the process of developing vehicle models for the different tools is discussed in detail, along with theprocedure of validating the vehicle models.In the second part, the concept of Collision Avoidance Driver Assistance (CADA) function isintroduced and possible approaches for developing CADA functions are discussed in brief. It isimportant to note that the CADA functions in this work are based on cornering the vehicle i.e.maneuvering around the threat, rather than solely reducing vehicle speed. A number ofimplementations of the functions are developed in Simulink. A frequency analysis of a simplifiedlinear vehicle model is performed to investigate the influence of steering, differential braking, andtheir combination on the resultant lateral displacement of the vehicle during an evasive maneuver.The developed CADA functions are then simulated using the vehicle simulation tools. Two specificmetrics - Lateral Displacement gain and DeltaX - are formulated to evaluate the effectiveness of theCADA functions. Based on these metrics, the assistance obtained due to the functions for a specificevasive maneuver is compared.From the evaluation process of the three tools, two were considered suitable for the purpose ofsimulating collision avoidance functions. The evaluation of the CADA functions demonstrates thatcombined assistive steering with differential braking provides considerable assistance in order toavoid collisions. The simulation results also present interesting trends which provide a usefuldirection regarding the conditions for intervention by such collision avoidance functions during anevasive maneuver. The use of simulation tools makes it possible to observe these trends and utilizethem in the development process of the functions.

  • 186.
    Shekhar, Rudrendu
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Stability Analysis during Active Tire Excitation for Friction Estimation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Road accidents have been a persistent cause of death worldwide, and claim millions of lives everyyear. Recent developments in the active safety systems like Electronic Stability Control (ESC) havehelped in reducing these numbers quite signicantly over the years. However, a major challenge forthese systems is to know the friction coecient between the tire and the road, as this value limits theamount of force the tires can generate. Knowledge of the coecient of friction can be used to adaptthe driving style, thereby avoiding interventions by stability control at the limit, making vehiclessafer. However, it is a major challenge within the automotive industry to estimate the coecientof friction accurately, and with sucient availability, as that requires high levels of tire utilization,such that the tire is forced to reach the non-linear range of operation. Such events are very rarein everyday driving, and requires a system induced active excitation of the tires. One such methodthat has been proposed earlier, to carry out an active tire excitation, is by using a simultaneouspropulsive and brake force on front and the rear the axles. However, applying an equal magnitudeof propulsive and brake force results in a force neutral situation at the vehicle level, which forcesthe velocity to be constant, overriding driver acceleration requests. Thus, an active tire excitationmethod was proposed by Volvo Cars, which is able to apply an unequal propulsive and brake forceto the front and the rear axle, such that the driver's acceleration demand can be met, during frictionestimation. However, such an excitation can be dangerous to carry out, if it leads to instability ofthe vehicle.Several methods have been developed to analyze and quantify stability of a vehicle, but detailedanalysis about the stability under forced excitation, for friction estimation, is very rare. This thesiswork investigates the lateral stability of a vehicle undergoing an active tire excitation for frictionestimation. The objective is to understand which vehicle and tire models can be used to quantifythe lateral stability of a vehicle under forced excitation, and how phase portrait methods can beused to develop a stability monitor that is able to indicate the lateral stability of the vehicle undera forced excitation.The results of using a stability monitor during active tire excitation clearly show that it is able toindicate when the vehicle becomes unstable and looses control. It also shows that for slow speedsteady-state maneuvers and straight line maneuvers, the stability monitor does not indicate instability.A comparison between phase portrait based and conventional side-slip based stability monitorsshow the eectiveness and generality of the phase portrait based monitor, which is able to detectinstability earlier than the conventional side-slip based method.

  • 187.
    Spiric, Goran
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Algorithm evaluation for road anomaly detection and wear estimation on trucks using an accelerometer2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The condition of the roads is a factor that may not only affect the wear of a vehicle, car or truck, but as well may reduce fuel consumption, increase comfort, lower noise and maybe most importantly increase traffic safety. This gives a need of a system that can measure road quality and detect potholes, which could be of interest to haulers and to local road authorities that would get valuable information of road sections that are in need of maintenance.

    In this Master Thesis different algorithms were developed, and tested, that could automatically detect different kind of road anomalies using only an three-axis accelerometer mounted on the chassis of heavy duty trucks from Scania. Data collection was performed using two different trucks and the road anomalies were noted by the co-driver using the keyboard of a laptop. This Master Thesis also explored the correlation between the acceleration levels on the chassis and high elongation values on the front leaf spring.

    Using a developed evaluation framework, the anomaly detections from the different algorithms were compared to the test oracle to determine if the anomaly detection given by the algorithm was a true positive hit or a false positive. A great advantage of the developed evaluation framework is that additional algorithms could easily be added for evaluation. For the evaluation of the algorithms the statistical F-measure, which is the harmonic mean of the precision and sensitivity, was used for the test’s accuracy of the algorithms.

    The two algorithms that had the best performance results regarding detection of road anomalies were Algorithm – T and Algorithm – SDT. These two algorithms had a F-measure score of 65% and 64% respectively when the precision and sensitivity were equally weighted.

    For the correlation between acceleration levels and high elongation levels, Algorithm – SDT scored the highest F-measure value of 14%. This value is far from satisfying and a reason for the low value is that the algorithms were primarily developed for detection of road anomalies.

  • 188.
    Stensson Trigell, Annika
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Boij, Susann
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strömningsakustik.
    Efraimsson, Gunilla
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Jerrelind, Jenny
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Wennhage, Per
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Göransson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Numerisk akustik.
    ECO2 Vehicle Design: an initiative for a holistic perspective on future vehicle concepts2008Konferansepaper (Annet vitenskapelig)
  • 189.
    Stensson Trigell, Annika
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Nybacka, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Ingvarsson, Hans
    Strategy for the KTH Transport Platform2010Rapport (Annet vitenskapelig)
    Abstract [en]

    To build on existing research excellence and strength, KTH has defined five distinct research focus areas: Transport, Energy, Materials, Information and Communication Technology, and Medical and Biomedical Technology. Here, the KTH Transport Platform sets the scene for KTH’s present and future role in society within the transport area. A starting point is that KTH today possesses both broad and in-depth expertise within several key areas of transport research. The problems and challenges confronting future transport are however so complex that no player is able to solve them alone. Therefore, it is necessary to employ a multidisciplinary and a multi-stakeholder approach. On this background the aim is to establish a joint passion and a unique mechanism for holistic transport research, demonstration and innovation together with partners in research community, industry and public bodies. The five thematic research areas within the KTH Transport Platform are: The Holistic Transport System Approach,The Future Transportation Infrastructure,Innovative Vehicle Concepts, Transport in the Information Era and Policy and Institutional Frameworks. The mission of the KTH Transport Platform is to be an effective and efficient vehicle for delivering multidisciplinary research aiming for transport solutions servicing the society of tomorrow. The expected outcome is an increased success in large, complex research applications due to good knowledge about societal and industrial needs with a focus on innovation. To conclude, there is a need for an initiative with passion for joint transport innovation. Here the word “joint” stands for both multi-disciplinary and multi-stakeholder approaches, with all parties involved committed to these.

  • 190.
    Stensson Trigell, Annika
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Rothhämel, Malte
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Pauwelussen, Joop
    Kural, Karel
    Advanced vehicle dynamics of heavy trucks with the perspective of road safety2017Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 55, nr 10, s. 1572-1617Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents state-of-the art within advanced vehicle dynamics of heavy trucks with the perspective of road safety. The most common accidents with heavy trucks involved are truck against passenger cars. Safety critical situations are for example loss of control (such as rollover and lateral stability) and a majority of these occur during speed when cornering. Other critical situations are avoidance manoeuvre and road edge recovery. The dynamic behaviour of heavy trucks have significant differences compared to passenger cars and as a consequence, successful application of vehicle dynamic functions for enhanced safety of trucks might differ from the functions in passenger cars. Here, the differences between vehicle dynamics of heavy trucks and passenger cars are clarified. Advanced vehicle dynamics solutions with the perspective of road safety of trucks are presented, beginning with the topic vehicle stability, followed by the steering system, the braking system and driver assistance systems that differ in some way from that of passenger cars as well.

  • 191.
    Su, He, Zhicheng, Xuxin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Links between Subjective Assessments and Objective Metrics for Steering2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The characteristics of vehicle steering perception are decisive factors concerning vehicle safety and overall pleasure behind the wheel. It is a challenge for vehicle manufacturers to achieve these features and qualities, because usually vehicle tuning almost only relies on subjective evaluation of test drivers, which is costly and time consuming. In order to optimize suspension design and develop a tool that can be used to evaluate steering with objective metrics instead of subjective assessment, links between them must be confirmed.

    In this master thesis, both objective and subjective testing data of over 20 vehicles across four different segments are introduced in linear and nonlinear analysis. Linear regression analysis is applied to investigate simply positive or negative correlation between a pair of subjective-objective parameters. However, even if certain linear correlations are obtained, it is still hard to define the optimal value for objective metrics. Considering that the general shape of a correlation function can reveal which objective range give higher subjective rating, it is possible to define these preferred ranges with Neural Network (NN). The best data available is adopted from three drivers who tested 15 sedans, and some interesting results are found.

    The initial results demonstrate that NN is a powerful tool to uncover and graphically illustrate the links between objective metrics and subjective assessments, i.e., the specific range leading to better steering feel. Given a larger sample size, more reliable and optimal links can be defined by following the same method. These confirmed links would enable vehicle dynamics engineers to more effectively develop new vehicles with nearly perfect steering feel.

  • 192.
    Sun, Peikun
    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.
    Jerrelind, Jenny
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Jonasson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik. Volvo Cars, Gothenburg, Sweden.
    Exploring the potential of camber control to improve vehicles' energy efficiency during cornering2018Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, nr 4, artikkel-id 724Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Actively controlling the camber angle to improve energy efficiency has recently gained interest due to the importance of reducing energy consumption and the driveline electrification trend that makes cost-efficient implementation of actuators possible. To analyse how much energy that can be saved with camber control, the effect of changing the camber angles on the forces and moments of the tyre under different driving conditions should be considered. In this paper, Magic Formula tyre models for combined slip and camber are used for simulation of energy analysis. The components of power loss during cornering are formulated and used to explain the influence that camber angles have on the power loss. For the studied driving paths and the assumed driver model, the simulation results show that active camber control can have considerable influence on power loss during cornering. Different combinations of camber angles are simulated, and a camber control algorithm is proposed and verified in simulation. The results show that the camber controller has very promising application prospects for energy-efficient cornering.

  • 193. Sundström, Peter
    et al.
    Jonasson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Andreasson, Johan
    Stensson Trigell, Annika
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Jacobsson, Bengt
    Path and control optimisation for over-actuated vehicles in two safety-critical maneuvres2010Inngår i: Proceedings of 10th International Symposium on Advanced Vehicle Control, AVEC´10 / [ed] Tim Gordon and Matt Best, Loughborough University and the Society of Automotive Engineers of Japan, Inc. , 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents results on how to optimally negotiate two safety-critical vehicle maneuvers, depending on different set of actuators. The motives for this research has been to provide viable knowledge of limitations of vehicle control under the presence of preview sensors, such as radar, camera and navigation. Using tools available in the JModelica.org platform, an optimal path is found by optimising the sequence of actuator requests during the maneuver. Particular interest is paid on the optimal trade-off between braking and steering.

  • 194.
    Svahn, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    On the stability and control of piecewise-smooth dynamical systems with impacts and friction2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis concerns the analysis of dynamical systems suitable to be modelled by piecewise-smooth differential equations. In such systems the continuous-in-time dynamics is interrupted by discrete-in-time jumps in the state or governing equations of motion. Not only can this framework be used to describe existing systems with strong nonlinear behaviour such as impacts and friction, but the non-smooth properties can be exploited to design new mechanical devices. As suggested in this work it opens up the possibility of, for example, fast limit switches and energy transfer mechanisms.

    Particularly, the dynamics at the onset of low-velocity impacts in systems with recurrent dynamics, so called grazing bifurcations in impact-oscillators, are investigated. As previous work has shown, low-velocity impacts is a strong source of instability to the dynamics, and efforts to control the behaviour is of importance. This problem is approached in two ways in this work. One is to investigate the influence of parameter variations on the dynamic behaviour of the system. The other is to implement low-cost control strategies to regulate the dynamics at the grazing bifurcation. The control inputs are of impulsive nature, and utilizes the natural dynamics of the system to the greatest extent.

    The scientific contributions of this work is collected in five appended papers. The first paper consists of an experimental verification of a map that captures the correction to the smooth dynamics induced by an impact, known in the literature as the discontinuity map. It is shown that the lowest order expansion of the map accurately captures the transient growth rate of impact velocities. The second paper presents a constructive proof of a control algorithm for a rather large class of impact oscillators. The proof is constructive in the sense that it gives control parameters which stabilizes the dynamics at the onset of low-velocity impacts. In the third paper a piecewise-smooth quarter-car model is derived, and the control strategy is implemented to reduce impact velocities in the suspension system. In the fourth and fifth papers the grazing bifurcation of an impact oscillator with dry friction type damping is investigated. It turns out that the bifurcation is triggered by the disappearance of an interval of stable stick solutions. A condition on the parameters of the system is derived which differentiates between stable and unstable types of bifurcation scenarios. Additionally, a low-cost control strategy is proposed, similar to the one previously mentioned, to regulate the bifurcation scenario.

  • 195.
    Svahn, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Dankowicz, Harry
    Controlled onset of low-velocity collisions in a vibro-impacting system with friction2009Inngår i: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 465, s. 3647-3665Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the onset of low-velocity, near-grazing collisions in an example vibro-impacting system with dry friction with particular emphasis on feedback control strategies that regulate the grazing-induced bifurcation behaviour. The example system is characterized by a twofold degeneracy of grazing contact along an extremal stick solution that is shown to result in a locally one-dimensional and piecewise-linear description of the near-grazing dynamics. Explicit control strategies are derived that ensure a persistent, low-impact-velocity, steady-state response across the critical parameter value corresponding to grazing contact even in instances where the dynamics in the absence ofcontrol exhibit a sudden transition to a high-impact-velocity response.

  • 196.
    Svahn, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Dankowicz, Harry
    Energy Transfer in Vibratory Systems with Friction Exhibiting Low-velocity Collisions2008Inngår i: Journal of Vibration and Control, ISSN 1077-5463, E-ISSN 1741-2986, nr 1-2, s. 255-284Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the dynamic response of an initially stationary part of a mechanism in the presence of a restoring force and dry friction to low-velocity collisions with a relatively more massive oscillating element. Of particular interest is the persistence of a local attractor in the motion of the less massive part as the path of the oscillating element grows to encompass the entire set of possible equilibrium positions in the absence of contact. It is argued that loss of a local attractor and the associated large-amplitude oscillations of the less massive part affords a means for energy transfer through the mechanism and a means for energy damping. The paper contains a rigorous derivation of conditions that appear sufficient for the persistence of a local attractor in the case where the massive oscillating element is replaced by an oscillating rigid unilateral constraint corresponding to an infinite mass ratio. Numerical simulations are subsequently used to investigate the response in the case where the mass ratio is assumed finite.

  • 197.
    Svahn, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Hamberg, J.
    Flight-path control of a missile using the Passive Normal Form2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of controlling the flight-path angle of a missile by means of a systematic use of passivity. A simple model of a generic missile's motion in a vertical plane based on wind tunnel data is used. A variant of backstepping is introduced, based on the novel concept of Passive Normal Form, by which explicit robustness margins are obtained. The method is applied to a variety of problems, including the use of dynamical extensions.

  • 198.
    Svahn, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Jerrelind, Jenny
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Dankowicz, Harry
    University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, Illinois, USA.
    Suppression of bumpstop instabilities in a quarter-car model2009Inngår i: Non-smooth Problems in Vehicle Systems Dynamics: Proceedings of the Euromech Colloquium, Berlin Heidelberg: Springer-Verlag , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Vehicle manufacturers are constantly pushed to reduce the aerodynamic drag of vehicles, for example by constructing lower vehicles with less road clearance. This, however, reduces the available margin for oscillations within the suspension. If the oscillation amplitude exceeds a critical value, the suspension will impact a bumpstop. Under periodic excitation, the onset of low-velocity impacts is associated with a strong instability in favor of high-velocity impacts. Such impacts reduce comfort and could be damaging to the vehicle. Efforts should therefore be made to limit impact velocities with the bumpstop, for example by suppressing the instability associated with low-velocity impacts. This paper proposes a low-cost feedback-control strategy, based on making small adjustments to the position of the bumpstop, that serve to suppress the transition to high-velocity impacts with the bumpstop in the case of periodic excitation. The control law is derived from the theory of discontinuity maps. The results demonstrate that the feedback strategy works even when wheel-hop is present.

  • 199.
    Svensson, Johan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Design of a portable steering wheel angle measurement system2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this Master Thesis is to develop a steering wheel measuring system. The system should be easy to use and install, portable and have the possibility to be used in different vehicle types from different manufactures. The old system in use is stationary equipment that is difficult to apply on a new vehicle without any major installation.

    In this work a prototype is developed using rate sensor technology. The system is based on two different angular rate sensors. One sensor is mounted on the steering wheel to record the motions the driver affects on the steering wheel. The second sensor is mounted fixed in the vehicle to record the movement of the vehicle. The signals are conditioned and combined before conversion into the steering wheel angle. The system is compatible with Race Technology DL2 data logger.

    The work presented shows that the design of the prototype works satisfactory, although with some limitations. Further development has to be done to make the system able to measure higher steering wheel angular velocities. Additional sensors can also be embedded in the system to minimize the signal conditioning after the measurements.

  • 200.
    Sällberg, Emil
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Ekman, Robert
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Vehicle Dynamics of a Jumping Rallycross Car2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis was performed in collaboration with Öhlins Racing AB. The company provides suspension systems to the automotive industry and to motorsport teams globally. Many of Öhlins’ customers compete in rallycross, a style of competition that generally involves highly modified production cars racing on closed, elevated and mixed surfaced circuits. Rallycross cars generally have an inherent problem and tend to over rotate mid-air after taking off from a jump. The vehicle often lands with a large pitch angle, damaging suspension components or losing valuable time when the driver waits for the vehicle to settle. The request from Öhlins was to analyse this phenomenon. The scope of the master thesis was to; investigate four different simulation software and choose the most appropriate software to simulate a rallycross car, perform a parameter study to analyse which parameters affect the jumping behaviour of the vehicle and study the force build up in the suspension during the landing phase. The four simulation software investigated were LMS Amesim, CarSim, Adams/Car and a 2D MATLAB model. The models were parameterised with vehicle data acquired from a rallycross car and validated against measured data obtained from tests with the same car. The MATLAB model was considered to be the best performing model given the criteria which were set up. A parameter study was conducted with the chosen simulation model where different vehicle parameters, driver behaviour and road profiles were analysed to investigate what impact they had on the jumping performance of the rallycross car. It could be concluded that the rear damper stiffness is critical for the jumping behaviour of the vehicle and that a stiffer rear damper generally gives the best performance. The longitudinal position of the centre of gravity also has a significant impact on vehicle jumping where a position in the middle between front and rear axle is preferred. The force build-up in the vehicle suspension was also analysed. Vehicle jumping and landing behaviour was compared to measurements from a human jumping in order to investigate if a human jumping utilised other force build-up strategies. It was found that the car force build-up during landing was similar to a human beings. Other force build-up strategies for the dampers were tested and it was found that dampers reacting to stroke position or hub acceleration can improve jumping performance of a rallycross car.

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