Friction Estimation for 4WD Vehicles and Detection of Partial Aquaplaning

With the development of ADAS and fully automated vehicles, information about tire-road contact and especially the friction potential is becoming particularly important. While human drivers have a certain feeling for the limits of safe vehicle operation based on their experience and perception, artificial systems rely entirely on the quantification of measured or estimated parameters.

The research project focuses on effect-based friction potential estimation methods. Effect-based methods usually require persistent excitation of forces, accelerations, etc., to rapidly and reliably detect friction parameters and adapt to their changes. Usual driving manoeuvres in public traffic rarely exhibit necessary levels and changes of tyre force and vehicle reaction, reducing the availability of these parameters or making their determination even impossible.

A new method for AWD vehicles is introduced and studied, which builds on the active excitation of longitudinal tyre forces in a way that persistent excitation needed for the algorithm is generated. The forces on both axles are slightly varied, while their sum is kept at the level to maintain the desired vehicle acceleration and the intervention is not recognized. The idea allows friction potential estimation at very low levels of longitudinal acceleration, or even at constant driving or decelerating, and requires no longitudinal velocity for slip calculation.

During wet road conditions, if the water on the road forms a continuous layer, aquaplaning can occur as a special case of friction potential reduction. The tyre squeezes the water out of its contact area, resulting in a hydrodynamic pressure distribution altering the tyre forces and (partially) lifting the tyre from the ground. This results in a reduction of friction potential with increasing velocity and water height, which eventually leads to a total loss of tangential tyre forces and, therefore, loss of controllability or stability.

Several typical effects that come along with (partial) aquaplaning are combined to allow for the automatic detection of partial aquaplaning before full and dangerous aquaplaning occurs. The information may then be used to warn the driver or adapt wheel slip control systems.

Figure 1: Testing on roads with different levels (0.8-2mm) of water height

References

Fichtinger, Andreas, Johannes Edelmann, Manfred Plöchl, Manuel Höll, and Michael Unterreiner. "Slip slope change detection based on active drive force excitation., opens an external URL in a new window" Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering (2023): 09544070231197378.

Fichtinger, Andreas, Ádám Bárdos, Zsolt Szalay, Johannes Edelmann, and Manfred Plöchl. "Pneumatic Tyre Aquaplaning: an Experimental Investigation on Manifestations and Influences of Appearance., opens an external URL in a new window" Acta Polytechnica Hungarica 19, no. 9 (2022): 45-65.

Fichtinger, Andreas, Johannes Edelmann, Manfred Plochl, and Manuel Holl. "Aquaplaning detection using effect-based methods: an approach based on a minimal set of sensors, electronic stability control, and drive torques., opens an external URL in a new window" IEEE Vehicular Technology Magazine 16, no. 3 (2021): 20-28.

Researcher

• Andreas Fichtinger

Project Partners

• Porsche
• Cariad