Arto Niskanen

Three 3-axis accelerometers fixed inside the tyre for studying contact patch deformations in wet conditions

The tyre–road contact area was studied visually by means of a high-speed camera and three accelerometers fixed to the inner liner of the tyre carcass. Both methods show a distorted contact area in wet conditions, but interesting differences appeared. First, the contact area in full aquaplaning seems strongly distorted on a glass plate when subjected to visual inspection, while the accelerometers indicate a more even hydrodynamic aquaplaning contact length (CL) across the tyre width. Secondly, the acceleration sensors predict the clear shortening of the CL of the tyre before the critical aquaplaning speed. It can be concluded that the visual contact area and shape are heavily dependent on the transparency of the liquid and smoothness of the glass. Meanwhile, the tyre sensors can provide a CL estimate on any road surface imaginable.

Three Three-Axis IEPE Accelerometers on the Inner Liner of a Tire for Finding the Tire-Road Friction Potential Indicators

Direct tire-road contact friction estimation is essential for future autonomous cars and active safety systems. Friction estimation methods have been proposed earlier for driving conditions in the presence of a slip angle or slip ratio. However, the estimation of the friction from a freely-rolling tire is still an unsolved topic. Knowing the existing friction potential would be beneficial since vehicle control systems could be adjusted before any remarkable tire force has been produced. Since accelerometers are well-known and robust, and thus a promising sensor type for intelligent tires, this study uses three three-axis IEPE accelerometers on the inner liner of a tire to detect friction potential indicators on two equally smooth surfaces with different friction levels. The equal roughness was chosen for both surfaces in order to study the friction phenomena by neglecting the effect of surface texture on vibrations. The acceleration data before the contact is used to differentiate the two friction levels between the tire and the road. In addition, the contact lengths from the three accelerometers are used to validate the acceleration data. A method to differentiate the friction levels on the basis of the acceleration signal is also introduced.

Energy harvesting system for intelligent tyre sensors

An intelligent tyre system enables the active chassis control system to directly access the information about tyre-road interactions. However, supplying power to the system is still a bottleneck which limits the applicability of the intelligent tyre system. This paper proposes a piezoelectric energy harvesting system with energy storage to address this issue. The system was installed to the inside of a car tyre and measured with a chassis dynamometer. The harvester was found to produce approximately 88 μW of power at a driving speed of 60 km/h, which is enough to supply energy for a low-power in-tyre sensor system with radio link connectivity such as a tyre pressure monitoring system.

Towards the friction potential estimation: A model-based approach to utilizing in-tyre accelerometer measurements

Tyre-road contact condition information would benefit many vehicle safety and control systems. However, direct information is still not available in production vehicles. Tyre sensing could provide this necessary information but many aspects must still be studied. In this paper, a physical ring tyre model is used to estimate and remove the acceleration profile caused by the contact deformation from the measured in-tyre acceleration data. This residual acceleration can then be used to study the tyre-road contact conditions. A simple analysis with standard deviation is used to show the effects of different road surfaces on the measured in-tyre acceleration.

Accelerometer tyre to estimate the aquaplaning state of the tyre-road contact

Ever increasing amount of Advanced Driver Assisting Systems (ADAS) are being developed to improve the safety of the vehicles. However, the direct information of the tyre-road contact is not available for these systems. An intelligent tyre has been proposed to provide that information in many studies. This paper focuses on water and aquaplaning detection with an intelligent tyre with three triaxial accelerometers attached on the inner liner. A method to detect the tyre-road contact state is introduced and validated with experimental data.