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Controlling over-actuated road vehicles during failure conditions
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.ORCID iD: 0000-0001-7427-2584
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of electrification of chassis and driveline systems in road vehicles is to reduce the global emissions and their impact on the environment. The electrification of such systems in vehicles is enabling a whole new set of functionalities improving safety, handling and comfort for the user. This trend is leading to an increased number of elements in road vehicles such as additional sensors, actuators and software codes. As a result, the complexity of vehicle components and subsystems is rising and has to be handled during operation. Hence, the probability of potential faults that can lead to component or subsystem failures deteriorating the dynamic behaviour of road vehicles is becoming higher. Mechanical, electric, electronic or software faults can cause these failures independently or by mutually influencing each other, thereby leading to potentially critical traffic situations or even accidents. There is a need to analyse faults regarding their influence on the dynamic behaviour of road vehicles and to investigate their effect on the driver-vehicle interaction and to find new control strategies for fault handling.

A structured method for the classification of faults regarding their influence on the longitudinal, lateral and yaw motion of a road vehicle is proposed. To evaluate this method, a broad failure mode and effect analysis was performed to identify and model relevant faults that have an effect on the vehicle dynamic behaviour. This fault classification method identifies the level of controllability, i.e. how easy or difficult it is for the driver and the vehicle control system to correct the disturbance on the vehicle behaviour caused by the fault.

Fault-tolerant control strategies are suggested which can handle faults with a critical controllability level in order to maintain the directional stability of the vehicle. Based on the principle of control allocation, three fault-tolerant control strategies are proposed and have been evaluated in an electric vehicle with typical faults. It is shown that the control allocation strategies give a less critical trajectory deviation compared to an uncontrolled vehicle and a regular electronic stability control algorithm. An experimental validation confirmed the potential of this type of fault handling using one of the proposed control allocation strategies.

Driver-vehicle interaction has been experimentally analysed during various failure conditions with typical faults of an electric driveline both at urban and motorway speeds. The driver reactions to the failure conditions were analysed and the extent to which the drivers could handle a fault were investigated. The drivers as such proved to be capable controllers by compensating for the occurring failures in time when they were prepared for the eventuality of a failure. Based on the experimental data, a failure-sensitive driver model has been developed and evaluated for different failure conditions. The suggested fault classification method was further verified with the conducted experimental studies.

The interaction between drivers and a fault-tolerant control system with the occurrence of a fault that affects the vehicle dynamic stability was investigated further. The control allocation strategy has a positive influence on maintaining the intended path and the vehicle stability, and supports the driver by reducing the necessary corrective steering effort. This fault-tolerant control strategy has shown promising results and its potential for improving traffic safety.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xii, 84 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2015:23
Keyword [en]
vehicle dynamics, vehicle safety, driver-vehicle interaction, failure analysis, wheel hub motor failure, over-actuation, fault-tolerant control
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
URN: urn:nbn:se:kth:diva-166819ISBN: 978-91-7595-597-1 (print)OAI: oai:DiVA.org:kth-166819DiVA: diva2:812521
Public defence
2015-06-05, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 09:30 (English)
Opponent
Supervisors
Note

QC 20150520

Available from: 2015-05-20 Created: 2015-05-19 Last updated: 2015-05-20Bibliographically approved
List of papers
1. Survey on fault-tolerant vehicle design
Open this publication in new window or tab >>Survey on fault-tolerant vehicle design
2012 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Fault-tolerant vehicle design is an emerging inter-disciplinary research domain, which is of increasedimportance due to the electrification of automotive systems. The goal of fault-tolerant systems is to handleoccuring faults under operational condition and enable the driver to get to a safe stop. This paperpresents results from an extended survey on fault-tolerant vehicle design. It aims to provide a holisticview on the fault-tolerant aspects of a vehicular system. An overview of fault-tolerant systems in generaland their design premises is given as well as the specific aspects related to automotive applications. Thepaper highlights recent and prospective development of vehicle motion control with integrated chassiscontrol and passive and active fault-tolerant control. Also, fault detection and diagnosis methods arebriefly described. The shift on control level of vehicles will be accompanied by basic structural changeswithin the network architecture. Control architecture as well as communication protocols and topologiesare adapted to comply with the electrified automotive systems. Finally, the role of regulations andinternational standardization to enable fault-tolerant vehicle design is taken into consideration.

Keyword
reliability, safety, wheel hub motor, diagnosis, control system, fault-tolerant control
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-98811 (URN)2-s2.0-84877594122 (Scopus ID)
Conference
26th Electric Vehicle Symposium, (EVS26), Los Angeles, CA, May 6-9, 2012
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

Qc 20120730

Available from: 2012-07-30 Created: 2012-07-03 Last updated: 2015-05-20Bibliographically approved
2. Fault classification method for the driving safety of electrified vehicles
Open this publication in new window or tab >>Fault classification method for the driving safety of electrified vehicles
2014 (English)In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 52, no 5, 704-732 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Taylor & Francis, 2014
Keyword
Vehicle safety, vehicle dynamics, fault analysis, fault classification, electric vehicles, ISO 26262
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-131222 (URN)10.1080/00423114.2014.889317 (DOI)000337583100006 ()2-s2.0-84901643352 (Scopus ID)
Note

QC 20140509. Updated from manuscript to article in journal

Funder: Swedish Hybrid vehicle Center

Available from: 2013-10-10 Created: 2013-10-10 Last updated: 2017-12-06Bibliographically approved
3. Single wheel hub motor failures and their impact on vehicle and driver behaviour
Open this publication in new window or tab >>Single wheel hub motor failures and their impact on vehicle and driver behaviour
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This research work studies the impact of single wheel hub motor failures on the dynamic behaviour of electric vehicles and the corresponding driver reactions. An experimental study in a moving-base driving simulator is conducted to analyse the inuence of single wheel hub motor failures for motorway speeds. Driver reaction times are derived from the measured data and discussed in their experimental context. The failure is rated objectively on the dynamic behaviour of the vehicle and compared to the subjective evaluation. Findings indicate that critical trac situations impairing trac safety can occur for motorway speeds. Clear counteractions by the drivers had to be taken.

Keyword
Vehicle safety, wheel hub motor failure, vehicle dynamics, failure analysis, electric vehicle, driver reaction time, controllability class, ISO 26262, driving simulator
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-166822 (URN)
Note

QS 2015

Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2015-05-20Bibliographically approved
4. Experimental study on single wheel hub motor failures and their impact on the driver-vehicle behavior
Open this publication in new window or tab >>Experimental study on single wheel hub motor failures and their impact on the driver-vehicle behavior
Show others...
2016 (English)In: Proceedings of the ASME 2015 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2015, Boston, USA: ASME Press, 2016, UNSP V003T01A001Conference paper, Published paper (Refereed)
Abstract [en]

An experimental field study investigating the impact of single wheel hub motor failures on the dynamic behavior of a vehicle and the corresponding driver reaction is presented in this work. The experiment is performed at urban speeds on a closed off test track. The single wheel hub motor failure is emulated with an auxiliary brake system in a modified electric vehicle. Driver reaction times are derived from the measured data and discussed in their experimental context. The failure is rated and evaluated objectively based on the dynamic behavior of the vehicle. Findings indicate that driver reactions are more apparent for the accelerator pedal compared to the steering wheel response. The controllability evaluation of the vehicle behavior shows that no critical traffic situation occurs for the tested failure conditions. However, even small deviations of the vehicle can impair traffic safety, specifically for other traffic participants like bicyclist and pedestrians.

Place, publisher, year, edition, pages
Boston, USA: ASME Press, 2016
Keyword
Vehicle safety, wheel hub motor failure, vehicle dynamics, failure analysis, electric vehicle, driver reaction time, controllability class, ISO 26262, field study
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-166827 (URN)10.1115/DETC2015-46178 (DOI)000379883900001 ()2-s2.0-84979053767 (Scopus ID)
Conference
17th International Conference on Advanced Vehicle Technologies (AVT)
Note

QC 20150520

Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2016-08-23Bibliographically approved
5. Modelling and experimental evaluation of driver behaviour during single wheel hub motor failures
Open this publication in new window or tab >>Modelling and experimental evaluation of driver behaviour during single wheel hub motor failures
2015 (English)In: Proceedings of the 3rd International Symposium on Future Active Safety Technology Towards zero traffic accidents (FASTzero'15), 2015Conference paper, Published paper (Refereed)
Abstract [en]

A failure-sensitive driver model has been developed in the research study presented in this paper. The model is based on measurements of human responses to dierent failure conditions inuencing the vehicle directional stability in a moving-base driving simulator. The measurements were made in a previous experimental study where test subjects were exposed to three sudden failure conditions that required adequate corrective measures to maintain the vehicle control and regain the planned trajectory. A common driver model and a failure-sensitive driver model have been compared, and results for the latter agree well with the measured data. The proposed failure-sensitive driver model is capable of maintaining the vehicle control and regaining the planned trajectory similarly to the way in which humans achieved this during a wheel hub motor failure in one of the rear wheels.

Keyword
Driver model, human behaviour, wheel hub motor failure, driving simulator, vehicle dynamics
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-166829 (URN)
Conference
3rd International Symposium on Future Active Safety Technology Towards zero traffic accidents (FASTzero'15)
Note

QC 20150520

Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2015-05-20Bibliographically approved
6. Control allocation strategies for an electric vehicle with a wheel hub motor failure
Open this publication in new window or tab >>Control allocation strategies for an electric vehicle with a wheel hub motor failure
Show others...
2015 (English)In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 10, no 3, 263-287 p.Article in journal (Refereed) Published
Abstract [en]

Three fault-tolerant control strategies for electric vehicles with wheel hub motors are presented and compared, which are all based on the control allocation principle. The main objective is to maintain the directional stability of the vehicle in case of a component failure during high speed manoeuvres. Two simplified strategies that are suited for on-board implementation are derived and compared to an optimal control allocation strategy and a reference vehicle with a basic electronic stability control system. The occurring faults are considered to be in the electric high-voltage system that can arise in wheel hub motors. All three control allocation strategies show improved re-allocation of traction forces after a severe fault, and hence an improved directional stability. However, the performance of both simplified algorithms shows limitations in case of force demands outside the capabilities of the respective actuator. This work shows that vehicle safety is increased by the proposed fault-tolerant control strategies.

Place, publisher, year, edition, pages
InderScience Publishers, 2015
Keyword
Electric vehicles, Fault tolerance, Flight control systems, Traction control, Traction motors, Vehicle wheels, Vehicles, Wheels, Control allocation, Fault accommodation, Fault handling, Fault tolerant control, Integrated chassis controls, Inverter shut-down, Vehicle dynamics, Wheel-hub motors
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-166463 (URN)10.1504/IJVSMT.2015.070164 (DOI)2-s2.0-84934274855 (Scopus ID)
Funder
StandUp
Note

Updated from Accepted to Published. QC 20150701

Available from: 2015-05-11 Created: 2015-05-11 Last updated: 2017-01-10Bibliographically approved
7. Design and experimental evaluation of a fault-tolerant control strategy with and without a driver in the loop
Open this publication in new window or tab >>Design and experimental evaluation of a fault-tolerant control strategy with and without a driver in the loop
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this work, a fault-tolerant control strategy for an electric vehicle is developed and analysed for a wheel hub motor failure during a straight line driving manoeuvre. Based on the control allocation principle, an analytical approach is compared to an optimisation approach and both are investigated for their suitability to handle such failures. The analytical control allocation strategy has shown promising results similar to the optimal control allocation strategy. The improvements in vehicle stability and maintained desired path are also verified by experiments. The analytical approach is implemented in an experimental vehicle verifying the simulation results without driver in the loop. An experimental study including drivers is further conducted to analyse the influence of the control allocation strategy on the driver-vehicle interaction for the same manoeuvre. Further improvements for vehicle stability and lateral deviation are found for the driver study when an analytical control allocation strategy is included. The driver-vehicle interaction to a fault is improved strongly due to controller intervention. This fault-tolerant control strategy has shown promising results and its potential to improve traffic safety.

Keyword
fault handling, control allocation, electric vehicle, fault accommodation, vehicle dynamics, wheel hub motor failure, driver-vehicle interaction, experiment
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-166831 (URN)
Note

QP 2015

Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2015-05-20Bibliographically approved

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