Cameras recognise a specific splash and spray pattern of the tyres that can be aquaplaning in its early phase
Continental is developing ways to warn drivers about an imminent risk of aquaplaning. The aquaplaning assistance concepts use surround view camera images and signals from tyre-mounted sensors.
The holistic concept can give the driver time to prevent the front wheels of the vehicle from floating, while warning other vehicles to be prepared for a critical situation.
Dry, icy, snowy or wet: awareness of road conditions is a crucial safety factor as accidents in severe weather arise mainly due to significant loss of friction between tyres and the surface of the road. With its Road Condition Observer, Continental has introduced a system that allows road conditions to be classified with regard to tyre-road friction.
A specific situation called aquaplaning is extremely dangerous for manually driven vehicles as well as automated ones. Continental has now begun to develop sensor-based concepts to warn the driver in the event of imminent loss of friction. When there is a thick layer of water on the road, the water pressure between the tyre footprint and the road surface can make the front wheels float. Braking and steering are no longer possible, and the driver loses control of the vehicle.
“Wet road conditions are difficult for a car driver to evaluate,” said Bernd Hartmann, head of adas and tyre interactions at Continental. “Once you feel your vehicle floating, it is too late. Our aquaplaning assistance concepts detect the early aquaplaning phase to make the driver aware of what is going on under the tyres. This can help drivers or automated vehicles to adapt their speed appropriately to wet road conditions.”
The system under development is all encompassing – tyres, tyre-sensors, cameras, algorithms, brake actuation and the human-machine interface.
The company’s developers are focused on predicting and managing the risk of aquaplaning. The objective is to detect a possible front-wheels floating situation as early as possible to trigger an early warning to the driver. Using signals from surround view cameras and tyre-mounted etis (electronic tyre information system) sensors, an early warning concerning the approaching aquaplaning situation is provided to the driver.
Continental is also working on the control and stabilisation of vehicles in aquaplaning situations, such as torque vectoring by individual wheel braking.
Aquaplaning conditions can also occur unexpectedly with no opportunity for advance warning. In such cases, the potential risk to other vehicles on the road can be mitigated by early communications via V2X technology, facilitating a network of solidarity where one vehicle acts as a safety sensor for all other vehicles and not just those in its direct vicinity. This information could be provided to vehicles that could potentially be affected, so they are able to adjust their driving functions to the aquaplaning conditions.
To detect aquaplaning situations, video images from surround-view cameras mounted in the side mirrors, the grille and rear are analysed.
“When there is a lot of water on the road, the camera images show a specific splash and spray pattern from the tyres that can be detected as aquaplaning in its early phase,” said Hartmann.
For example, excessive water displacement in all directions underneath the tyre is a characteristic attribute. During the first testing phase, the wetness recognition algorithms delivered a very high hit ratio in predicting potential aquaplaning conditions.
In addition to image information, Continental uses information from tyres to detect the risk of aquaplaning. In this concept, signals from the etis sensors, mounted on the tyre’s inner liner, are computed.
“We use the accelerometer signal from the electronic tyre information system to look for a specific signal pattern,” said Andreas Wolf, head of Continental’s body and security business unit.
A tyre model processes the incoming radial acceleration of the part of the tyre that is in contact with the road. For wet roads – when enough water is transported out of the tire tread to ensure an appropriate grip – the signal shows a distinct pattern. As soon as a wedge of water begins to form in front of the tyre footprint region and there is excessive water on the road, the acceleration signal begins to oscillate in a characteristic way, indicating an early risk of aquaplaning. Since the etis sensors can also detect the remaining tyre tread depth, a safe speed for a given wet road condition can be calculated and communicated to the driver.
Testing has shown that future aquaplaning assistance will also have the potential to intervene in an actual aquaplaning situation by applying the rear brakes in a controlled way to establish a degree of torque vectoring to maintain vehicle manoeuvrability within physical limits.
Not only is aquaplaning a challenge to the driver, but it is also difficult to pin down how many country road and highway accidents in wet road conditions are caused by floating front wheels.
“This is one of the last white spots on the strategic map towards greater road safety,” said Hartmann.
But drivers must continue to consider a general rule: adjusting their speed to wet roads and keeping an eye on the tyre’s tread depth. Since aquaplaning depends on tread depth, the height of the water on the road and speed, Continental recommends renewing summer tyres with three millimetres of residual tread depth. Below this limit, the risk of aquaplaning increases significantly.