Online and Offline Identification of Tyre Model Parameters
Doktorsavhandling, 2018

The accelerating development of active safety system and autonomous vehicles put higher requirements on both environmental sensing and vehicle state estimation as well as virtual verification of these systems. The tyres are relevant in this context due to the considerable influence of the tyres on the vehicle motion and the performance boundaries set by the tyres. All forces that the driver use to control the vehicle are generated in the contact patch between the tyre and the road on a normal passenger car. Hence, the performance limits imposed by the tyres should ideally be considered in the active safety systems and in self-driving vehicles. Due to tyres influence on the vehicle motions, they are some of the key components that must be accurately modelled to correlate complete vehicle simulations models with physical testing.

This thesis investigates the possibility to estimate the tyre-road friction coefficient during normal driving using active tyre force excitation, i.e. online identification of tyre model parameters. The thesis also investigates the possibility to scale tyre Force and Moment (F&M) models for complete vehicle simulations from indoor tests to real road surfaces using vehicle-based tyre testing, i.e. offline identification of tyre model parameters.

For online identification of tyre model parameters, the focus has been on how to perform tyre force excitation to maximize the information about the tyre-road friction coefficient. Furthermore, the required excitation level, as a ratio of the maximum tyre-road friction coefficient, for different road surfaces and tyre models have been evaluated for a larger number of passenger car tyres. The thesis shows the feasibility and benefits of using active tyre force excitations and illustrates its benefits when estimating the tyre-road friction coefficient by identifying nonlinear tyre model parameters. The method shows promising results by offering tyre-road friction estimates when demanded by the driver or an on-board system. This system can also be combined with other tyre-road friction estimates to offer a continuous tyre-road friction estimate, e.g. through car-to-car communication.

For offline identification of tyre model parameters, the focus was put on rescaling tyre models from indoor testing to a real-world road surface using vehicle-based tyre testing. Sensors were fitted to the vehicle to measure all inputs and outputs of the Pacejka 2002 tyre model. Furthermore, testing was performed on both different road surfaces and using different manoeuvres for tyre model identification. The effect on the complete vehicle behaviour in simulation when using tyre models based on different manoeuvres and road surfaces was investigated. The results show the importance of using a road surface and manoeuvre that are representative for the road surface and manoeuvre in which the vehicle will be evaluated. The sensitivity to different manoeuvres are mainly related to the changes in tyre properties with tyre surface temperature and the lack of temperature effects in the tyre model. The method shows promising results as an efficient way to rescale tyre models to a new road surface.

state estimation

computer aided engineering

tyre testing

parameter estimation

tyre-road friction estimation

active safety


vehicle dynamics

KA, Kemigården 4
Opponent: Professor Manfred Plöchl, Division of Technical Dynamics and Vehicle Dynamics, TU Wien, Austria.


Anton Albinsson

Chalmers, Mekanik och maritima vetenskaper, Fordonsteknik och autonoma system

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Tyre may not be regarded as the most interesting component to spend money on for most car owners. However, tyres are arguably some of the most important components on a car. When the driver requests a change in velocity through steering, braking or by pressing the accelerator pedal, these requests are met by the tyres generating a horizontal force. The total area in contact between the tyres and the road, for all fours wheels, are roughly the same as an A4 sheet of paper and the forces used to control the vehicle are all generated in this small area. The tyres influence not only how the car feels in normal driving situations. They also limit the maximum acceleration that the vehicle can achieve and thus the braking distance, maximum cornering velocity and the available traction.  

This thesis has investigated how tyre properties that directly affects the vehicle motion can be identified. Two situations have been investigated, the first one being in normal conditions when the vehicle is driven on public road. Focus has been given to identify the maximum force, given by the tyre-road friction coefficient, that the tyres can generate. Finding the peak achievable force require that the vehicle is close to utilizing these forces, or in other words, the vehicle must operate close to the limit. This is not the case for most normal driving situations. This issue has been addressed by introducing and investigating an invention that generate forces at the tires with the purpose of identifying the coeffect of friction. Results suggest that this could potentially be implemented in cars on the road and would enable the vehicle to probe the slipperiness of the road at any time.

The second situation of tyre property identification is related to vehicle motion simulations for improving the vehicle development process. The force that the tyres generate depend on the relative velocity between the tyre and the road. A mathematical model that connect the tyre motion and the tyre force can be identified based on test data. These tests are normally performed on special machines in a laboratory environment. The tyre models can then be used in vehicle simulations to predict the motion and response of the vehicle. This thesis has investigated a method where the tyres are tested directly on a test track with special sensors fitted to the vehicle. The test track is closer to the real conditions of which the tyres are used compared to the laboratory environment, governing for more accurate tyre models based on this data.

The results from this thesis can be used by car manufacturers and others to improve the prediction of vehicle motion in simulations and reducing development cost. By enabling a more efficient development process of for example active safety systems, these systems can be improved which could potentially reduce the number of injuries in road traffic accidents. The identification of the tyre performance limitation when the vehicle is driving on the road can be used by autonomous vehicles and active safety systems to predict the vehicle motion capabilities.







Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4401



KA, Kemigården 4

Opponent: Professor Manfred Plöchl, Division of Technical Dynamics and Vehicle Dynamics, TU Wien, Austria.

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