Significant effort has been made in the development of tyres and vehicles to optimize the safety, performance and economy in transportation. Throughout the vehicle development processes, the tyre is considered as a key component for the vehicle behaviour. However, the tyre-road contact is not being measured directly in the production vehicles even though it is the most important part of the vehicle dynamics providing all the forces to control a vehicle. Especially the autonomous vehicles require a reliable estimate of road friction potential for safe operation in varying conditions. Intelligent tyre research is aiming for sensing the tyre-road contact with different sensors embedded in the tyre. Accelerometers are potential production tyre sensors as well as powerful research tools for tyre development. In this thesis, a tyre with accelerometers mounted on the inner liner is used to study the effects of aquaplaning and friction potential on the measured accelerations. Accelerometer tyre measurements were conducted with traditional high-speed imaging on a liquid covered glass plate to study aquaplaning. The contact lengths determined from the tangential acceleration showed clearly the shortening of the contact due to the hydrodynamic lift. In addition, the distorted contact shape was visible with both methods. It is shown that the accelerometer tyre can provide powerful tool for the tyre aquaplaning research on real road surfaces. In addition, a method to detect the presence of water in the contact from the lateral acceleration signal was suggested vehicle safety systems in mind. A simplified flexible ring model was utilized for interpreting the radial acceleration data. The acceleration profile derived from the model could be used to remove the effect of contact deformation from the measured signal dominating the effects of more subtle phenomena such as friction potential. Difference in the contact mechanism on different surfaces were observed from the estimated model parameters and a reliable way to estimate the contact length was obtained by using the model-based approach. The effects of friction potential were studied on equally smooth surfaces with different friction levels as well as on real road surfaces with varying roughness, friction and deformability levels. First, the vibration in the pre-contact part was found to exist on low-friction surface excited by the local sliding of the tread. On real road surfaces, the surface roughness dominates this effect and Hilbert-Huang transform was utilized to detect even more subtle vibration in the contact. The local sliding was found to occur inside the contact resulting in low-amplitude high-frequency vibration. This was observed on the freely rolling tyre, which highlights the potential of tyre sensing.The thesis presents methods and applications for utilization of accelerometer as a tyre sensor to develop a tyre of 21st century – an Intelligent Tyre.
|Translated title of the contribution||Rengas-tiekontaktin aistiminen älykkäällä renkaalla|
|Publication status||Published - 2017|
|MoE publication type||G5 Doctoral dissertation (article)|
- intelligent tyre
- tyre-road contact
- friction potential