If you ever drive on the motorway, you will surely have had this unpleasant experience: the moment when your car begins to glide on a wet road surface, when all of a sudden you are only a passenger and your car no longer reacts to steering commands. Welcome to the world of aquaplaning. So when the heavens open, it makes no difference whether a good or bad driver is caught in the downpour. When it comes to physics, we are all in the same boat - no pun intended! That is when it gets really wet on the road.
So for this reason, together with Porsche, we have taken the "wetness detection" function into series production, thus supporting the world premiere known as the "Porsche WET mode". This application has enabled the German car manufacturer to develop a new assistance function for its current Porsche 911, a function that is designed to make driving even safer.
This really works because the innovation is able to recognise distinct wetness on the road surface. It triggers a preventive measure to regulate the driving systems which then aim at more stable driving behaviour. In this way it is hoped to detect the gliding of a vehicle in wet conditions at an early stage and ideally to prevent any critical situations from arising.
An essential component of the innovational system is the SHAKE structure-borne sound sensor (short for Structural Health and Knock Emission) developed by HELLA. Installed in the front wheel arch liners of the Porsche 911, the sensor recognises the road condition and detects the film of water on the road surface. By means of a piezoelectric element, the SHAKE sensor detects vibrations and airborne noise from water droplets swirled up in the air and from this information determines the degree of wetness between the tyres and the road.
If the system of the new Porsche 911 detects a wet road on the basis of the information obtained, the response behaviour of the Porsche Stability Management (PSM) and of the Porsche Traction Management (PTM) becomes preconditioned. The driver also receives a warning and the recommendation to switch to WET mode. Then, for example, the response behaviour of the drive adapts to the situation in order to ensure the greatest possible driving stability.
The wetness sensor also offers great potential when it comes to autonomous driving. "Because in order to be able to determine static friction and thus braking distances, precise information about road conditions is vital. This is exactly what the SHAKE sensor can reliably determine," explains a convinced Michael Jaeger, member of the HELLA Electronics Management Board who is responsible for actuators and sensor systems. Small sensor, huge potential.