| 1. |
- Wanner, Daniel, et al.
(author)
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Survey on fault-tolerant vehicle design
- 2012
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In: World Electric Vehicle Journal. - : The World Electric Vehicle Association (WEVA). - 2032-6653. ; 5:2, s. 598-609
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Journal article (peer-reviewed)abstract
- Fault-tolerant vehicle design is an emerging inter-disciplinary research domain, which is of increased importance due to the electrification of automotive systems. The goal of fault-tolerant systems is to handle occuring faults under operational condition and enable the driver to get to a safe stop. This paper presents results from an extended survey on fault-tolerant vehicle design. It aims to provide a holistic view on the fault-tolerant aspects of a vehicular system. An overview of fault-tolerant systems in general and their design premises is given as well as the specific aspects related to automotive applications. The paper highlights recent and prospective development of vehicle motion control with integrated chassis control and passive and active fault-tolerant control. Also, fault detection and diagnosis methods are briefly described. The shift on control level of vehicles will be accompanied by basic structural changes within the network architecture. Control architecture as well as communication protocols and topologies are adapted to comply with the electrified automotive systems. Finally, the role of regulations and international standardization to enable fault-tolerant vehicle design is taken into consideration.
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| 2. |
- Davari, Mohammad Mehdi, et al.
(author)
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Investigating the potential of wheel corner modules in reducing rolling resistance of tires
- 2014
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In: FISITA 2014 World Automotive Congress - Proceedings. - : FISITA.
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Conference paper (peer-reviewed)abstract
- The improvement in tire rolling efficiency is one of the key elements to optimize the fuel economy and thereby reduce the vehicle emissions. Earlier efforts to reduce the rolling resistance have mainly been focusing on new materials in the tire compounds. The overall research aim of this study is to present the potentials of implementing innovative chassis concepts with the focus on Wheel Corner Modules (WCM) by describing the possibilities in affecting rolling resistance and relating them to previous research findings. The core idea of the concept is to actively control and actuate all degrees of freedom in the wheel i.e. implementing steering, suspension and propulsion functions into a unique module which can be implemented in each corner of the vehicle. Using this concept the limitations of traditional wheel kinematics can be resolved extensively. This article presents the first step towards creating a vehicle simulation model that can show how the WCM functionality can influence the rolling resistance. A model of loss is chosen after analysing the behaviour of a three different rubber models and then implemented into a brush tire model. An effective way, but less complicated compared to current methods, to introduce the loss into tire model is presented. In conventional suspensions, the design is compromising between for example safety, comfort and rolling resistance, etc. at all driving conditions. However, using the WCM, the possibility of achieving a better compromise between those objectives is possible.Finally, based on WCM functionalities a plausible control architecture is proposed.
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| 3. |
- Davari, Mohammad Mehdi, et al.
(author)
-
Investigating the Potential of Wheel Corner Modules in Reducing Rolling Resistance of Tyres
- 2014
-
In: Proceedings of FISITA "14 World Automotive Congress, Maastricht, Netherlands (2014).
-
Conference paper (peer-reviewed)abstract
- The improvement in tire rolling efficiency is one of the key elements to optimize the fuel economy and thereby reduce the vehicle emissions. Earlier efforts to reduce the rolling resistance have mainly been focusing on new materials in the tire compounds. The overall research aim of this study is to present the potentials ofimplementing innovative chassis concepts with the focus on Wheel Corner Modules (WCM) by describing thepossibilities in affecting rolling resistance and relating them to previous research findings. The core idea of theconcept is to actively control and actuate all degrees of freedom in the wheel i.e. implementing steering,suspension and propulsion functions into a unique module which can be implemented in each corner of the vehicle. Using this concept the limitations of traditional wheel kinematics can be resolved extensively. This article presents the first step towards creating a vehicle simulation model that can show how the WCM functionality can influence the rolling resistance. A model of loss is chosen after analysing the behaviour of three different rubber models and then implemented into a brush tire model. An effective way, but less complicatedcompared to current methods, to introduce the loss into tire model is presented. In conventional suspensions, thedesign is compromising between for example safety, comfort and rolling resistance, etc. at all drivingconditions. However, using the WCM, the possibility of achieving a better compromise between those objectivesis possible. Finally, based on WCM functionalities a plausible control architecture is proposed.
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| 4. |
- Edrén, Johannes, 1983-
(author)
-
Exploring force allocation control of over actuated vehicles
- 2011
-
Licentiate thesis (other academic/artistic)abstract
- As the concern for environmental changes and diminishing oil resources grows more and more, the trend of new vehicle concepts now includes full electric or partly electric propulsion systems. The introduction of electric power sources enables more advanced motion control systems due to electrification of the vehicle's actuators, such as individual wheel steering and in wheel hub motors. This can enable a control methodology that uses different chassis control strategies into a system that will be able to fully utilise the vehicle. Due to this, future vehicles can be more optimised with respect to energy consumption, performance and active safety. Force allocation control is a method that distributes the wheel forces to produce the desired response of the vehicle. In order to evaluate if this methodology can be implemented in future series production vehicles, the aim of this work is to explore how force allocation control can be utilised in a real vehicle to improve vehicle dynamics and safety. In order to evaluate different approaches for generic vehicle motion control by optimization, modelling and simulation in combination with real vehicle experiments will be needed to fully understand the more complex system, especially when actuator dynamics and limitations are considered. The use of a scale prototype vehicle represents a compromise between development cost, efficiency and accuracy, as it allows realistic experiments without the cost and complexity of full vehicle test. Moreover since the vehicle is unmanned it allows studies of at-the-limit situations, without the safety risks in full vehicle experiments. A small scale prototype vehicle (Hjulia) has been built and equipped with autonomous corner module functionality that enables individual control of all wheels. A cost effective force allocation control approach has been implemented and evaluated on the prototype vehicle, as well as in vehicle simulation. Results show improvement of stopping distance and vehicle stability of a vehicle during split-m braking. The aspects of vehicle dynamic scaling are also discussed and evaluated, as it is important to know how the control implementation of small scale prototype vehicles compares with full size vehicles. It is shown that there is good comparison between vehicles of different scales, if the vertical gravitational acceleration is adjusted for. In Hjulia, gravity compensation is solved by adding a specific lifting rig. Studies of vehicles considering optimal path tracking and available actuators are also made to evaluate control solutions of evasive manoeuvres at low and high friction surfaces. Results show differences in how the forces are distributed among the wheels, even though the resulting global forces on the vehicle are approximated to be scaled by friction. Also it is shown that actuator limitations are critical in at-the-limit situations, such as an obstacle avoidance manoeuvre. As a consequence these results will provide good insights to what type of control approach to choose to handle a safety critical situation, depending on available actuators. The built prototype vehicle with implemented force allocation control has shown to be a useful tool to investigate the potential of control approaches, and it will be used for future research in exploring the benefits of force allocation control.
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| 5. |
- Edrén, Johannes, 1983-, et al.
(author)
-
Implementation and evaluation of force allocation control of a down-scaled prototype vehicle with wheel corner modules
- 2013
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In: International Journal of Vehicle Systems Modelling and Testing. - 1745-6436. ; 8:4, s. 335-363
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Journal article (peer-reviewed)abstract
- The implementation of wheel corner modules on vehicles creates new possibilities of controlling wheel forces through the utilisation of multiple actuators and wheel motors. Thereby new solutions for improved handling and safety can be developed. In this paper, the control architecture and the implementation of wheel slip and chassis controllers on a down-scaled prototype vehicle are presented and analysed. A simple, cost-effective force allocation algorithm is described, implemented and evaluated in simulations and experiments. Straight line braking tests were performed for the three different controller settings individual anti-lock brakes (ABS), yaw-torque-compensated ABS and force allocation using both wheel torque and steering angle control at each wheel. The results show that force allocation is possible to use in a real vehicle, and will enhance the performance and stability even at a very basic level, utilising very few sensors with only the actual braking forces as feedback to the chassis controller.
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| 6. |
- Edrén, Johannes, 1983-
(author)
-
Motion modelling and control strategies of over-actuated vehicles
- 2014
-
Doctoral thesis (other academic/artistic)abstract
- With the growing concern for environmental change and uncertain oil resources, the development of new vehicle concepts will in many cases include full or partial electric propulsion. The introduction of more advanced powertrains enables vehicles that can be controlled with a variety of electric actuators, such as wheel hub motors and individual steering. With these actuators, the chassis can be enabled to adjust its properties depending on the driving situation.Manoeuvring of the vehicle, using for example electric propulsion, braking, suspension, steering and camber control may also allow a variety of combinations which, if properly utilised, can increase the outer limits of vehicle performance and safety. The fact that the vehicle has a greater number of actuators than required to control a certain number of degrees of freedom is called over-actuation. Since there is a great need for energy optimised vehicles, energy efficient control is also required. For this reason, this work is about the allocation of wheel forces can improve safety, performance and energy efficiency in future electrified vehicles in different driving situations.Studies of optimally controlled vehicles show that performance, safety and efficiency can be improved by utilising available actuators in over-actuated vehicles. Path tracking and optimal actuator control signals are evaluated in evasive manoeuvres at low and high friction surfaces. The results show how the forces are distributed differently among the wheels, even though the resulting global forces on the vehicle are similar. Optimal control of camber angles and active suspension show that vehicle performance and safety can be greatly improved. The limits of tyre forces can be increased and better utilised in a way that a passive system is unable to achieve. Actuator performance is also shown to be important, however even low actuator performance is shown to be sufficient to improve vehicle performance considerably. Energy efficiency is also improved as unnecessary vehicle motions are minimised during normal driving and wheel forces are used in a better way.Simplified algorithms to control available actuators, such as wheel angles, vertical actuation and propulsion torques, have been developed, based on the analysis of the results of the optimisation studies. Analyses of the impact of these simplifications have been made. For the cases studied, it has been shown that it is possible to get significantly better performance at reasonable levels of actuator performance and control complexity. This helps to simplify the introduction of this technology in electrified vehicles.Control allocation is a method that distributes the wheel forces to produce the desired response of the vehicle. Simplified control allocation algorithms are proposed that allocate wheel forces in a way that resembles the behaviour of the optimisation solutions. To be able to evaluate the applicability of this methodology for implementation in vehicles, a small-scale prototype vehicle with force allocation control possibilities has been designed and built. The vehicle is equipped with autonomous corner module functionality that enables individual control of all wheels regarding steering, camber, propulsion/braking and vertical loads. Straight-line braking tests show that force allocation can be used in a real vehicle and will enhance performance and stability even at a very basic level, using few sensors with only the actual braking forces as feedback.In summary, this work has contributed to a better understanding of how the allocation of wheel forces can improve vehicle safety, performance and energy efficiency. Moreover, it has contributed to increased understanding of how vehicle motions should be modelled and simulated, and how control strategies for over-actuated vehicles can be made more suitable for implementation in future electrified vehicles.
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| 7. |
- Edrén, Johannes, 1983-, et al.
(author)
-
Road friction effect on the optimal vehicle control strategy in two critical manoeuvres
- 2014
-
In: International Journal of Vehicle Safety. - 1479-3105 .- 1479-3113. ; Vol. 7:No. 2, s. pp 107-130
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Journal article (peer-reviewed)abstract
- This paper presents a research study on the optimal way to negotiate safety-critical vehicle manoeuvres depending on the available actuators and road friction level. The motive is to provide viable knowledge of the limitations of vehicle capability under the presence of environmental preview sensors. In this paper, an optimal path is found by optimising the sequence of actuator requests during the manoeuvres. Particular attention is paid to how the vehicle control strategy depends on friction. This study shows that the actuation of all the forces and torques on and around the vehicle centre of gravity is approximately scaled with friction, whereas at individual wheel level, the optimal force allocation will differ under different friction conditions. A lower friction level leads to lower velocities and load transfer, which influences the individual wheels’ tyre force constraints. However, the actuator response compared to the whole system is increased at a lower friction level.
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| 8. |
- Edrén, Johannes, 1983-, et al.
(author)
-
The developement of a down-scaled over-actuated vehicle equipped with autonomous corner module functionality
- 2010
-
In: FISITA Proceedings 2010, paper F2010B056.
-
Conference paper (peer-reviewed)abstract
- This paper presents the development of a functional down-scaled prototype of a passenger car with capability to control steering, wheel torques, wheel loads and camber individually. The adopted chassis technology is based on a modularised platform, referred to as Autonomous corner modules (ACM), which simplifies the re-use of components at the four corners of the vehicle and between different vehicles.This work gives an insight in the design of the vehicle and the selection of electrical actuators and sensors to provide all ACM functions. Since a part of the implemented chassis components do not admit to be scaled down at the same level, necessary design modifications are suggested. The problems of scaling, meaning that a down-scaled prototype cannot fully emulate a full-scaled vehicle’s all functions simultaneously, are a great disadvantage of down scaling. For example is gravity one desired parameter that is hard to physically scale down.In order to evaluate the behaviour of the down-scaled prototype, it is of high importance to establish the characteristics of the developed vehicle and its subsystems. In particular, tyre design is considered as complex. For this reason, different ideas of methods to confirm tyre characteristics are proposed.Also the paper presents the initial process of developing the prototype vehicle that is later to be used in vehicle dynamics research.
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| 9. |
- Edrén, Johannes, 1983-, et al.
(author)
-
Utilization of Vertical Loads by Optimization for Integrated Vehicle Control
- 2012
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In: Proceedings of AVEC12, 11th Symposium on Advanced Vehicle Control, September 9-12, Seoul, Korea, 2012..
-
Conference paper (other academic/artistic)abstract
- This paper presents results on how to optimally utilise vertical loading on individual wheels in order to improve vehicle performance during limit handling. Numerical optimisation has been used to find solutions on how the active suspension should be controlled and coordinated together with friction brakes and electric power assisted steering (EPAS). Firstly, it is investigated whether the brake distance can be shortened. Secondly, the performance during an evasive manoeuvre is investigated. The result shows that brake distance can be improved by at least 0.5 m and the speed through the evasive manoeuvre by roughly 1 km/h for the studied vehicle. Quick actuators is shown to give even better performance. These results provide guidance on how active suspension can be used to give significant improvements in vehicle performance.
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| 10. |
- Erséus, Andreas, et al.
(author)
-
A path tracking driver model with representation of driving skill
- 2011
-
In: International Journal of Vehicle Systems Modelling and Testing. - 1745-6436. ; 6:2, s. 145-186
-
Journal article (peer-reviewed)abstract
- A flexible and intuitive non-linear driver model is proposed, which allows setting of physically relevant parameters for representation of both typical high and typical low skill drivers in a path tracking scenario with constant speed. The model is equipped with a relatively simple internal vehicle model and is divided into three levels of driving skill: perceptual, anticipatory and interpretational skill; decisional skill; and execution skill. Validation of the model is performed using the results from moving base driving simulator tests with the double lane change scenario described in ISO 3888-1:1999. The parameter sets used for the model configuration are selected based on physical relevance to the model and optimisation is carried out with a Nelder-Mead implementation, showing that the model is able to resemble the characteristics of the driver types in the scenario for 70 km/h, and with adjustments being able to represent drivers at other speeds.
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| 11. |
- Erséus, Andreas, 1975-
(author)
-
Driver-Vehicle Interaction : Identification, Characterization and Modelling of Path Tracking Skill
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- Since the dawn of the automobile, driver behaviour has been an issue. Driving can result in accidents that may harm not only the driver but also passengers and the surroundings. This calls for measures that restrict the usage of vehicles and to assist the individual driver to conduct the driving in a safe, yet practically efficient manner. The vehicles should therefore be both safe and intuitive, and preferably answer to thedifferent needs of all kinds of drivers. Driving skill can be defined in many ways, depending on the objective of the driving task, but answer in some way to the question of how well the driver can conduct the driving task. To assist low skill drivers without compromising the driving demand for high skill drivers, it is of highest importance that vehicles are tested and designed to meet those needs. This includes both the testing activities in the vehicle design phase in general but also the configuration for active systems and preventive safety, preferable with settings that adapts to the skill of the individual driver. The work here comprises the definition of skill and of driver recruitment procedures, scenario design, the development of an analysis method for objective measures, and the gathering of metrics to characterize the driver skill. Moreover, a driver model has been developed that makes use of driver skill characteristics. To gather the information needed, extensive multidisciplinary literature studies were conducted, as well as using field tests and test using an advanced moving base driving simulator. Here the focus is on path tracking skill, which is the main control aspect of driving, although the developed driving scenarios allow a varying degree of path planning, which is more related to regulation. The first simulator test was done with a very simple criterion fordriver selection, but the results gave a good insight into the variation between drivers ingeneral. For the following tests the recruitment procedure was refined to find drivers with high or low vehicle control and regulation skill, a recruitment that also was verified to really represent two different populations. A method was defined that successfully identified sets of skill-related measures, with some variation in composition depending on the path tracking demand on the driver. Int he curving road scenario, for example, the highest number of skill-related measures is identified in the curves, which is reasonable since the straight segments do not require the same amount of active control from the drivers. The driver model developed uses a quasi-static analytical description of the driver knowledge of the vehicle dynamics, but possesses the capability of nonlinear descriptions. The parameters in this model are mainly physical properties that easily can be related to the driving process. Metrics gathered are used for identification of the driver model setup for a double lane change scenario using an optimization routine, with adjusted parameter settings for different velocities. With a subjective comparison of the recorded driving simulator data, the method is verified to enable driver skill settings for driver models. In addition, the method allows metrics to be gathered for driver skill identification routines, meeting the defined objectives of the project.
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| 12. |
- Erséus, Andreas, et al.
(author)
-
Methodology for finding parameters related to path tracking skill applied on a DLC-test in a moving base driving simulator
- 2013
-
In: International Journal of Vehicle Autonomous Systems. - 1471-0226 .- 1741-5306. ; 11:1, s. 1-21
-
Journal article (peer-reviewed)abstract
- The objective of this research is to develop and assess a method that can evaluate the relation of the driver's path tracking skill to a large number of vehicle parameters. The proposed methodology for comparison of measures under equal conditions is applied on test data from a double lane change test in a moving base simulator. Several measures are found to separate the recruited high and low skill driver groups, with the best results for the second part of the manoeuvre. Standard deviation qualifies for successful driver skill categorisation using commonly sampled data, e.g., steering wheel rate and angular acceleration.
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| 13. |
- Jerrelind, Jenny, et al.
(author)
-
Exploring active camber to enhance vehicle performance and safety
- 2013
-
Conference paper (peer-reviewed)abstract
- The aim of this study is to evaluate optimal active camber strategies for improvement of vehicle performance and safety during limit handling. Numerical optimisation is used to find solutions on how the active camber should be controlled and coordinated in cooperation with individual braking and front axle steering. Based on the characteristics of a multi-line brush tyre model, a Simple Magic Formula description is developed where camber dependency, load sensitivity and first order speed dependent relaxation dynamics are included. The vehicle is analysed during an evasive manoeuvre when the vehicle is running at the limit. It is evident from the results that active camber control can improve safety and performance during an avoidance manoeuvre.
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| 14. |
- Jerrelind, Jenny, et al.
(author)
-
Simulation of Vehicle-Overhead Power System Interaction on Electric Roads
- 2012
-
In: Proceedings of the Mini Conference on Vehicle System Dynamics, Identification and Anomalies.
-
Conference paper (peer-reviewed)abstract
- Due to the upcoming lack of oil and the environmental problems that conventional internal combustion engines are causing, electric vehicles have gained a growing interest during recent years. One solution to improve the efficiency of the existing road network is to make use of electric roads equipped with an overhead power system, thereby allowing also long-distance truck and bus transports to be powered by electricity without the need of heavy, bulky and expansive batteries.Providing electric power using an overhead power system has primarily been used in railway applications and only to some extent in road applications, for example in the case of trolley buses in urban areas. In this study, an overhead catenary system providing electric power to a long-distance truck by means of a pantograph mechanism that collects power through sliding contact with the overhead wire is analysed through simulation.A model of a truck equipped with a pantograph is developed and its interaction with an overhead catenary system model is simulated using the finite element method. The current collection quality is evaluated by analysing the pantograph-catenary contact force variation during the influence of different disturbances such as road irregularities and contact wire vibrations due to multiple pantographs.The study is an assessment of the possibility of using a conventional overhead power system developed for trains in a new context by providing power to long-distance road transports. The results show that the investigated disturbances influence the dynamics of the studied truck-pantograph-catenary system, nevertheless the contact force variation is within the allowed range according to the technical specifications for interoperability (TSI) for trains. It can be concluded that an overhead power system is a promising solution for a more environmentally friendly energy supply for trucks and buses at specific road sections.
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| 15. |
- Jonasson, Mats, 1969-, et al.
(author)
-
Global force potential of over-actuated electric vehicles
- 2010
-
In: International Journal of Vehicle System Dynamics. - : Informa UK Limited. - 0042-3114. ; 48:9, s. 983-998
-
Journal article (peer-reviewed)abstract
- This paper formulates force constraints of over-actuated road vehicles. In particular, focus is put on different vehicle configurations provided with electrical drivelines. It is demonstrated that a number of vehicles possesses non-convex tyre and actuator constraints, which have an impact on the way in which the actuators are to be used. By mapping the actuator forces to a space on a global level, the potential of the vehicle motion is investigated for the vehicles studied. It is concluded that vehicles with individual drive, compared with individual brakes only, have a great potential to yaw motion even under strong lateral acceleration.
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| 16. |
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| 17. |
- Jonasson, Mats, 1969, et al.
(author)
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Investigation of the Non-Convex Force Constraints Imposed by Individual Wheel Torque Allocation
- 2010
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In: Vehicle System Dynamics. - 1744-5159 .- 0042-3114. ; 48:9
-
Journal article (peer-reviewed)abstract
- This paper formulates force constraints of over-actuated road vehicles. In particular, focus is put on different vehicle configurations provided with electrical drivelines. It is demonstrated that a number of vehicles possesses non-convex tyre and actuator constraints, which have an impact on the way in which the actuators are to be used. By mapping the actuator forces to a space on a global level, the potential of the vehicle motion is investigated for the vehicles studied. It is concluded that vehicles with individual drive, compared with individual brakes only, have a great potential to yaw motion even under strong lateral acceleration.
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| 18. |
- Jonasson, Mats, 1969-, et al.
(author)
-
Utilization of Actuators to Improve Vehicle Stability at the Limit : From Hydraulic Brakes Toward Electric Propulsion
- 2011
-
In: Journal of Dynamic Systems Measurement, and Control. - : ASME. - 0022-0434 .- 1528-9028. ; 133:5
-
Journal article (peer-reviewed)abstract
- The capability of over-actuated vehicles to maintain stability during limit handling is studied in this paper. A number of important differently actuated vehicles, equipped with hydraulic brakes toward more advanced chassis solutions, are presented. A virtual evaluation environment has specifically been developed to cover the complex interaction between the driver and the vehicle under control. In order to fully exploit the different actuators setup, and the hard nonconvex constraints they possess, the principle of control allocation by nonlinear optimization is successfully employed. The final evaluation is made by exposing the driver and the over-actuated vehicles to a safety-critical double lane change. Thereby, the differently actuated vehicles are ranked by a quantitative indicator of stability.
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| 19. |
- Morales Sanchez, Francisco, et al.
(author)
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Problems in using individual X-by-wire cornering modules
- 2014
-
In: International Journal of Heavy Vehicle Systems. - 1744-232X. ; 21:1, s. 1-10
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Journal article (peer-reviewed)abstract
- This article discusses some mechanical problems which occur by using hub-motors and individual wheel steering on road vehicles. Several multi-body dynamic simulations have been done in order to illustrate the high reaction forces in the steering actuator. This paper is not about an individual steering or control per se but aims to analyse the different forces in a given steering system for different steering scenarios.
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| 20. |
- Noréus, Olof, 1970-
(author)
-
Improving a six-wheeler’sperformance both on- and off-road
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- In vehicles with electric transmission and independent wheel stations, there is apossibility to control propulsion, steering and suspension individually for eachwheel. This makes it possible to improve mobility in terrain as well as performanceand driving safety on road. This contribution concerns how a six wheeledelectric transmission vehicle should be modelled to enable evaluation of thedynamic behaviour both in terrain and on road. This is made by combiningmodelling of vehicle, transmission and tyre/terrain behaviour.A tyre/terrain model is needed to simulate driving on soft ground. Heretyre/terrain models for simulating driving with both rigid and pneumatic wheelson soft ground have been developed. A method to measure terrain parametersand drawbar pull for a six-wheeled vehicle on sand is proposed, tested andevaluated.To simulate a six wheeled vehicle at the handling limit on road, a vehicle modelwith a brush tyre model is used in order to get physically reasonable simulationresults during high combined slip conditions. Different vehicle configurationsare considered, where front wheel steering is combined with eithersecond axle steering, rear wheel steering or individual wheel torque control.By applying different vehicle slip angles and thereby limiting the DOF of thevehicle model, the vehicle configurations are evaluated during different drivingconditions. The results show that by applying individual torque control to thefront wheel steered vehicle, the performance is improved for all evaluated manoeuvres,and the achievable aligning torque during a rear wheel skid increasessignificantly if the vehicle slip angle is larger than the maximum front wheelsteering angle.To conclude, models of a six-wheeled vehicle with electric transmission andtyre models both for soft and rigid ground have been developed. These modelsform a simulation platform, which makes it possible to evaluate controlstrategies for the electric transmission with the purpose to improve mobility interrain as well as performance and driving safety on road. Some examples ofapplications of the models are included, e.g. improving at-the-limit handlingand pivot turning performance.
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| 21. |
- Rehnberg, Adam, 1975-, et al.
(author)
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Scale model investigation of the snaking and folding stability of an articulated frame steer vehicle
- 2011
-
In: International Journal of Vehicle Systems Modelling and Testing. - : InderScience Publishers. - 1745-6436. ; 6:2, s. 126-144
-
Journal article (peer-reviewed)abstract
- 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.
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| 22. |
- Rehnberg, Adam, et al.
(author)
-
Snaking stability of articulated frame steer vehicles with axle suspension
- 2010
-
In: International Journal of Heavy Vehicle Systems. - 1744-232X. ; 17:2, s. 119-138
-
Journal article (peer-reviewed)abstract
- 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.
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| 23. |
- Rehnberg, Adam, 1975-
(author)
-
Suspension design for off-road construction machines
- 2011
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Doctoral thesis (other academic/artistic)abstract
- 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.
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| 24. |
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| 25. |
- Stensson Trigell, Annika, 1965-, et al.
(author)
-
Strategy for the KTH Transport Platform
- 2010
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Reports (other academic/artistic)abstract
- 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.
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| 26. |
- Sundström, Peter, et al.
(author)
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Path and control optimisation for over-actuated vehicles in two safety-critical maneuvres
- 2010
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In: Proceedings of 10th International Symposium on Advanced Vehicle Control, AVEC´10. - : Loughborough University and the Society of Automotive Engineers of Japan, Inc..
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Conference paper (peer-reviewed)abstract
- 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.
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| 27. |
- Wanner, Daniel, 1983-, et al.
(author)
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Fault classification method for the driving safety of electrified vehicles
- 2014
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In: Vehicle System Dynamics. - : Taylor & Francis. - 0042-3114 .- 1744-5159. ; 52:5, s. 704-732
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Journal article (peer-reviewed)abstract
- A fault classification method is proposed which has been applied to an electric vehicle. Potential faults in the different subsystems that can affect the vehicle directional stability were collected in a failure mode and effect analysis. Similar driveline faults were grouped together if they resembled each other with respect to their influence on the vehicle dynamic behaviour. The faults were physically modelled in a simulation environment before they were induced in a detailed vehicle model under normal driving conditions. A special focus was placed on faults in the driveline of electric vehicles employing in-wheel motors of the permanent magnet type. Several failures caused by mechanical and other faults were analysed as well. The fault classification method consists of a controllability ranking developed according to the functional safety standard ISO 26262. The controllability of a fault was determined with three parameters covering the influence of the longitudinal, lateral and yaw motion of the vehicle. The simulation results were analysed and the faults were classified according to their controllability using the proposed method. It was shown that the controllability decreased specifically with increasing lateral acceleration and increasing speed. The results for the electric driveline faults show that this trend cannot be generalised for all the faults, as the controllability deteriorated for some faults during manoeuvres with low lateral acceleration and low speed. The proposed method is generic and can be applied to various other types of road vehicles and faults.
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| 28. |
- Wanner, Daniel, 1983-, et al.
(author)
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Fault-Tolerant Control of Electric Vehicles with In-Wheel Motors through Tyre-Force Allocation
- 2012
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In: Proceedings of the 11th International Symposium on Advanced Vehicle Control. - Seoul : Japan Society of Mechanical Engineers (JSAE).
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Conference paper (peer-reviewed)abstract
- This paper presents a fault handling strategy for electric vehicles with in-wheel motors. The ap-plied control algorithm is based on tyre-force allocation. One complex tyre-force allocation meth-od, which requires non-linear optimization, as well as a simpler tyre force allocation method are developed and applied. A comparison between them is conducted and evaluated against a standard reference vehicle with an Electronic Stability Control (ESC) algorithm. The faults in consideration are electrical faults that can arise in in-wheel motors of permanent-magnet type. The results show for both tyre-force allocation methods an improved re-allocation after a severe fault and thus re-sults in an improved state trajectory recovery. Thereby the proposed fault handling strategy be-comes an important component to improve system dependability and secure vehicle safety.
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| 29. |
- Wanner, Daniel, 1983-
(author)
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Faults and their influence on the dynamic behaviour of electric vehicles
- 2013
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Licentiate thesis (other academic/artistic)abstract
- The increase of electronics in road vehicles comes along with a broad variety of possibilitiesin terms of safety, handling and comfort for the users. A rising complexityof the vehicle subsystems and components accompanies this development and has tobe managed by increased electronic control. More potential elements, such as sensors,actuators or software codes, can cause a failure independently or by mutually influencingeach other. There is a need of a structured approach to sort the faults from avehicle dynamics stability perspective.This thesis tries to solve this issue by suggesting a fault classification method and faulttolerantcontrol strategies. Focus is on typical faults of the electric driveline and thecontrol system, however mechanical and hydraulic faults are also considered. Duringthe work, a broad failure mode and effect analysis has been performed and the faultshave been modeled and grouped based on the effect on the vehicle dynamic behaviour.A method is proposed and evaluated, where faults are categorized into different levelsof controllability, i. e. levels on how easy or difficult it is to control a fault for the driver,but also for a control system.Further, fault-tolerant control strategies are suggested that can handle a fault with acritical controllability level. Two strategies are proposed and evaluated based on thecontrol allocation method and an electric vehicle with typical faults. It is shown thatthe control allocation approaches give less critical trajectory deviation compared to noactive control and a regular Electronic Stability Control algorithm.To conclude, this thesis work contributes with a methodology to analyse and developfault-tolerant solutions for electric vehicles with improved traffic safety.
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| 30. |
- Wanner, Daniel, 1983-, et al.
(author)
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Influence of vehicle parameters on directional stability during electric powertrain faults in passenger cars
- 2014
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In: Proceedings of the FISITA 2014 World Automotive Congress, Maastricht, The Netherlands, June 2-6, 2014. ; , s. 1-12
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Conference paper (peer-reviewed)abstract
- Electric powertrain faults that could occur during normal driving can affect the dynamic behaviour of the vehicle and might result in significant course deviations. The severity depends both on the characteristics of the fault itself as well as on how sensitive the vehicle reacts to this type of fault. In this work, a sensitivity study is conducted on the effects of vehicle design parameters, such as geometries and tyre characteristics, and fault characteristics. The vehicle specifications are based on three different parameter sets representing a small city car, a medium-sized sedan and a large passenger car. The evaluation criteria cover the main motions of the vehicle, i.e. longitudinal velocity difference, lateral offset and side slip angle on the rear axle as indicator of the directional stability. A design of experiments approach is applied and the influence on the course deviation is analysed for each studied parameter separately and for all first order combinations. Vehicle parameters of high sensitivity have been found for each criterion. The mass factor is highly relevant for all three motions, while the additional factors wheel base, track width, yaw inertia and vehicle velocity are mainly influencing the lateral and the yaw motion. Changes in the tyre parameters are in general less significant than the vehicle parameters. Among the tyre parameters, the stiffness factor of the tyres on the rear axle has the major influence resulting in a reduction of the course deviation for a stiffer tyre. The fault amplitude is an important fault parameter, together with the fault starting gradient and number of wheels with fault. In this study, it was found that a larger vehicle representing a SUV is more sensitive to these types of faults. To conclude, the result of an electric powertrain fault can cause significant course deviations for all three vehicle types studied.
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| 31. |
- Winkler, Niklas, et al.
(author)
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Aerodynamics of road vehicles in transient cross-winds-coupling aero to vehicle dynamics
- 2014
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In: Proceedings of the Mini Conference on Vehicle System Dynamics, Identification and Anomalies. - : Technical University of Budapest. - 9789633131862 ; , s. 63-70
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Conference paper (peer-reviewed)abstract
- Ground vehicles are sensitive to crosswinds, affecting aerodynamic and handling performance, and in some cases safety. Therefore it is important to be able to predict vehicle performance when exposed to crosswinds. The aim of the work presented in this paper is to assess the order of the model complexity in order to capture the vehicle behaviour during a transient crosswind event, regarding the interaction of the aerodynamic forces and the vehicle dynamic response. That is, the necessity to perform a full dynamic coupling instead of a static coupling to capture the vehicle performance both with respect to aerodynamics and the vehicle dynamics as is done today. The model used in the computations is based on the Ground Transportation System (GTS) model, which is simulated to run on a road passing a crosswind passage. The aerodynamic computations are performed using Detached Eddy Simulation (DES) coupled to a bicycle model for the vehicle dynamics. Here, two degrees of freedom are considered, that is, lateral translation and yaw motion. The change of the vehicle position in the aerodynamic domain is enabled through the use of the overset mesh technique. The results show that the full dynamic coupling is needed for large yaw angles of the vehicle, where the static coupling over-predicts the aerodynamic loads and in turn the vehicle motion.
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