The use of battery-free RFID pressure sensors could free the current TPMS solutions from their dependency of batteries while providing the same information.

The automotive industry has always been one of the sectors working with new technologies to deliver more value to their clients.

On top of that, regulatory bodies continue to establish more and more requirements to car manufacturers, mainly when it comes to security.

Tire Pressure Monitoring Systems (TPMS)

One of the requirements that has taken a larger media coverage has been the Tire Pressure Monitoring System (TPMS). It was thought primarily to prevent accidents caused due to incorrect pressure of the tires, which can greatly impact the driving experience of the user.

The idea is to show real time pressure of each tire in your car display. When pressure of any of the tires is lower than a safe value, the system will alert the driver so she can stop and correct the issue.

Car display TPMS

Car displaying TPMS information

There are different approaches to the technical solution but the one that’s being widely implemented is using wireless communications. A pressure sensor with an RF transmitter and a small battery are embedded in the tire. These send the information to an electronic central unit (ECU) that shows the desired information on your display.

Battery has always been a challenge for a number of factors – mainly the life-cycle of the solution and the issues with recycling the batteries. Using technology to help on this, new solutions have been developed where a battery-free system is used to ‘wake up’ the battery assisted system. This way the battery has a longer life-cycle but the issue with recycling is still there.

There have also been quite a lot of movements towards the energy harvesting topic. In principle, the fact that the wheels are spinning suggests that there is room for energy harvesting from vibrations (see a brief related article here). There have been different approaches in this direction but car manufacturers have turned them down so far.

Wireless TPMS solution

Wireless TPMS solution

Can battery-free sensors help?

Battery-free RFID sensor tags do both things at the same time – they communicate wirelessly and harvest energy – in a single system.

An RFID reader would send power and signal wirelessly to each pressure sensor tag in each of the wheels. The pressure sensor would get all energy required to function from the RF field of the reader so no battery would be required.

There are indeed lots of potential issues to address: from reader selection, frequencies, and protocols to testing performance at high speeds or extreme conditions but… Wouldn’t it be a good idea to have battery-free sensors inside your car?

Also note that once a reader is embedded in the car for the TPMS, other wireless and battery-free sensors can be implemented: temperature, pressure, load, switch status and any other sensors that would work without requiring any wires nor batteries. That means easier implementation and very little maintenance.

Sounds interesting, right?