Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Modelling of six-wheeled electric transmission terrain vehicle
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

In vehicles with electric transmission and independent wheel stations, it is possible to have a possibility to control propulsion, steering and suspension individually for each wheel. This makes it possible to improve mobility, performance and driving safety. The long term goal of this work is to develop a methodt hat can evaluate and improve the mobility of such vehicles in terrain. This contribution concerns how a six wheeled electric transmission vehicle should be modelled to enable evaluation of the dynamic behaviour in different type of terrain. This is made by combining modelling of vehicle, transmission and tire-terrain behaviour.

For wheeled vehicles an electric transmission with hub motors provides the ability to accurately control the torque on every wheel independently, giving a great ability to improve both mobility in terrain and vehicle behaviour on road. In this work the components of a diesel-electric powertrain for off-road vehicles are modelled and a control layout with the possibility to include functions for improved performance both while driving off- and on-road is proposed.

To handle driving on soft ground, a tire/terrain model is needed. The model should include lateral deformation in order to be able to steer. A tire/terrain model is derived based on the ideas of Wong and Reece. The terrain characteristics are chosen to be described by parameters according to the Bekker model, since this data are widely available in literature.

The developed tire/terrain model has been implemented together with a vehicle model. This terrain vehicle model is shown to be able to estimate sinkage, rolling resistance, traction force and steering characteristics, of a six wheeledterrain vehicle using electric transmission.

To conclude, models of a six-wheeled vehicle with electric transmission and tire models both for soft and rigid ground have been developed. These models form a simulation platform, which makes it possible to evaluate control strategies for the electric transmission with the purpose to improve mobility.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , iv, 36 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2007:05
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4291ISBN: 978-91-7178-579-4 (print)OAI: oai:DiVA.org:kth-4291DiVA: diva2:11670
Presentation
2007-02-22, Sal D41, KTH, Lindstedtsvägen 17, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101115Available from: 2007-03-01 Created: 2007-03-01 Last updated: 2010-11-15Bibliographically approved
List of papers
1. Six-wheeled vehicle steering
Open this publication in new window or tab >>Six-wheeled vehicle steering
2005 (English)In: Proceedings of the 15th International Conference of the ISTVS, 2005Conference paper, Published paper (Refereed)
Abstract [en]

Six-wheeled vehicles provide the ability to get high performance both on- and off-road. Ackermannsteering on six-wheeled vehicles is possible to achieve in several ways by steering on differentpair of wheels. The steering system has several contradicting demands such as volume saving wheelhouses, few actuators, small turning radius and fast lateral acceleration response. Some of the demandsare velocity dependent. Fast lateral acceleration response is important at high velocity, while a low turningradius is desired at low velocity. In this paper three different steering methods are considered: (a)steering on front and rear wheels, (b) steering on front and middle wheels and (c) steering only on thefront wheels. The steering methods are evaluated by simulating J-turn maneuvers in Matlab/Simulink andAdams. Considering turning radius, lateral acceleration and yaw rate it is shown that method (a) is best atlow speed, while method (b) gives the best stability at high speeds and method (c) uses few actuators andhas acceptable performance at high velocities. A drawback with method (c) is that the vehicle becomesmore sensitive to the load distribution, i.e. braking, accelerating and moving the load will affect steeringcharacteristics more for method (c) than for the other methods. A steering method using method (a) atlow speeds with a gradually transition to method (c) as the velocity increases is suggested.

Keyword
Six-wheeled vehicles, steering, modeling, simulation, lateral acceleration, stability
Identifiers
urn:nbn:se:kth:diva-6845 (URN)
Conference
Proceedings of the 15th International Conference of the ISTVS. Hayama, Japan September 25–29, 2005
Note
QC 20101026Available from: 2007-03-01 Created: 2007-03-01 Last updated: 2010-10-26Bibliographically approved
2. Simulation of electric transmission for off-road vehicle
Open this publication in new window or tab >>Simulation of electric transmission for off-road vehicle
2005 (English)In: Proceedings of the 15th International Conference ofthe ISTVS, 2005Conference paper, Published paper (Refereed)
Abstract [en]

Electric transmissions can be used both on tracked and wheeled vehicles. For wheeled vehiclesthe electric transmission with hub motors provides the ability to accurately control the torque on everywheel independently, giving a great ability to improve both mobility in terrain and vehicle behaviour onroad. In this paper the components of a diesel-electric powertrain for off-road vehicles are modeled anda control layout with the possibility to include functions for improved performance both while driving offandon-road is proposed. The modeled electrical machines are of permanent magnet type with switchingpower electronics for motor currents control. Since the aim is to provide a framework when developingcontrollers for improved vehicle behaviour the models are of mean value type and the switching operationis not included. Components included in the models are a diesel engine, permanent magnet generator,controlled rectifier in order to use full DC-link voltage even for low diesel rpm, DC-link and power electronicsfor drive motors with field weakening at high speeds. All models are simulated in Simulink togetherwith a simplified vehicle model and the results show that it is possible to control the transmission withsimple ramp limitations providing a great possibility to let the electric transmission stay partially functionalto inhibit damages in case of a main controller failure.

Keyword
Electric transmission, simulation, vehicle control
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-6846 (URN)
Conference
Proceedings of the 15th International Conference of the ISTVS. Hayama, Japan September 25–29, 2005
Note
QC 20101026Available from: 2007-03-01 Created: 2007-03-01 Last updated: 2010-10-26Bibliographically approved
3. Tire/terrain models for simulating six-wheeled vehicle on soft ground
Open this publication in new window or tab >>Tire/terrain models for simulating six-wheeled vehicle on soft ground
2006 (English)In: In Proceedings of the 10th European Conference of the ISTVS, 2006Conference paper, Published paper (Refereed)
Abstract [en]

This paper is a part of the work in the project “Cross CountryDriving Dynamics”, which is a project within the Swedish“Green Car”initiative.The purpose of the project is to find out how control of the electric transmissionfor terrain vehicles can be used to improve the off-road performance. In thefirst part of the project models for the vehicle are developed in order to beable to use simulations when developing control methods. The steering systemand simulations of the electric transmission were presented as two papers onISTVS in Japan 2005 and together with the tire/terrain models in this paperit is possible to simulate a six-wheeled vehicle with electric transmission onsoft ground. There are a lot of different purposes for tire/terrain models. Thesimplest models are created with the purpose to give a rough estimate of themobility of the vehicle on different terrains. FEM models on the other hand cangive deep insight in the interaction between tire and soil and also features of thetires. However, FEM models are computational intensive and therefore cannotbe practically used for vehicle simulations, but they can assist by providing datawhen developing models for such simulations. In vehicle simulations mainly thevertical force, rolling resistance, torque, sinkage and lateral force are of interest.Based on experimental data, Bekker has proposed a pressure-sinkage model,which can be used when predicting off-road vehicle performance. Beneath atire the soil will flow both in the lateral and longitudinal direction. In thelongitudinal direction, the soil will flow forwards and backwards in differentzones. Due to the two failure zones the pressure in the ground around the tirewill not increase with depth as in the pressure-sinkage model, but instead themaximum pressure will be at the point where the two failure zones join eachother. The position of that point depends on the slip of the wheel. Wongand Reece have proposed models for the pressure in the ground around a rigidwheel based on experimental results. When using pneumatic tires the tires willbe deflected where the pressure in the ground exceeds the sum of the inflationpressure and the pressure exerted by the tire carcass, which in turn affects thegeometry of the tire/terrain interaction and the pressure in the ground. Sincethe shear force in the ground is a function of the pressure, the tire slip and theshear modulus of the soil, it is possible to calculate the torque of the wheel andthe tractive force. It is possible to handle steering by adding a force ellipse tohandle lateral forces. In order to handle transients it is necessary to includedamping characteristics of the soil. The tire/terrain models are implementedtogether with a vehicle model and it is seen that the differential equations forsoft ground simulations are fairly stiff, but simulations show that it is possibleto solve them and get reasonable simulation speeds on a normal PC.

Keyword
Tire/terrain modeling
Identifiers
urn:nbn:se:kth:diva-6847 (URN)
Conference
In Proceedings of the 10th European Conference of the ISTVS, Budapest, Hungary October 3–6, 2006
Note
QC 20101026Available from: 2007-03-01 Created: 2007-03-01 Last updated: 2010-10-26Bibliographically approved

Open Access in DiVA

fulltext(547 kB)1634 downloads
File information
File name FULLTEXT01.pdfFile size 547 kBChecksum MD5
7fc207aaf6816ea5822340881b284def2f969cd41f7d625962c16bd0256132c3c6d0cac0
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Noréus, Olof
By organisation
Aeronautical and Vehicle Engineering
Mechanical Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 1634 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 682 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf