An innovative solution for one application can quickly breed new solutions to problems we didn’t even know we had. Take space exploration: who knew putting a man on the moon would give us non-stick frying pans and pressure-relieving mattresses?

Back on planet Earth, automotive sensors are evolving from their original design purposes—relating to regulatory compliance and safety—into a multitude of new applications. These range from reacting to weather conditions to alerting you that the vehicle needs servicing.

We are nowhere near exhausting the new capabilities we can give vehicles by embedding even more sensors than they already have. In some cases, it will be relatively easy to add new sensors, but the installation of some new sensor systems is contingent on improving in-vehicle connectivity and coming up with innovative powering options.

The industry is, in fact, innovating to bring more sensor-rich vehicles with new capabilities closer to reality.

 

The journey toward intelligence

The ability to interrogate sensors and interpret their data in real-time is opening up whole new ways in which vehicles and their occupants can interact—between humans and machines, and with the external environment.

Vehicles today typically contain more than 50 sensors. The enormous amount of data that can be collected from these sensors enables the automotive industry to make vehicles safer, cleaner, more efficient, and more comfortable.

Vehicle manufacturers use a variety of sensor technologies to monitor engine performance, fuel consumption and emissions, motion, speed, and geographical position, plus temperature, pressure, and airflow. There are sensors for the environmental conditions in the cabin and others that monitor driver alertness.

Data from temperature sensors are being applied to ensure that the cabin temperature is at optimum comfort levels for the occupants. Information from position sensors and GPS systems can now not only plot a route but also respond to real-time events such as congestion or accidents to ensure we reach our destinations with minimal delay.

However, it is the ability to embed intelligence, to locally convert the data from sensors to information, that will support the shift towards advanced driver assistance systems (ADAS), electric vehicles, mobility as a service, and ultimately autonomous vehicles (AVs).

ADAS relies on intelligence garnered from vehicle subsystems. However, these are among the sensors whose true potential is being restricted by inadequate power supply.

Tire pressure monitoring systems (TPMS) are a prime example. There is an abundance of data from the wheel and tire interaction with the driving surface, but the information available has been limited to tire pressure because TPMS and tire-mounted sensors must rely upon a small battery with a limited amount of power.

Localized computing and processing of rich and detailed data, and communication of this information at the speeds that will be necessary for ADAS and higher levels of AV capability, will require significantly more power than is currently available.

In addition, the various component capabilities need to be integrated to produce a system that is optimized for accuracy, latency, and efficiency.

The power to perform

The automotive industry and its vendors are together focused on improving the way in which these essential subsystems perform.

At TDK, for example, we have devised a self-powered sensor system that integrates multiple sensing capabilities, including tire pressure sensing and a “perpetual” power supply with edge compute and high-rate connectivity in one unit.

Called InWheelSense, it employs a piezoelectric energy harvesting (EH) module we developed to mount directly on vehicle wheels. The EH module uses the weight of the vehicle acting upon it as the wheel rotates to generate electricity.

The piezoelectric effect is the phenomenon whereby an electrical charge is produced when pressure is applied to a piezoelectric element. EH in a wheel has the great benefit of recharging the TPMS battery, eliminating the need for a battery replacement, which makes supplying more power to more tire sensors over the life of the tire a huge opportunity.

Because the device’s electromotive force changes with the status of the vehicle—such as changes in speed, turns, or slipping tires—it also becomes possible to sense not just simple tire pressure, but to provide holistic data pertaining to the running condition of the entire vehicle in real-time.

Measuring 125 mm x 28 mm x 19 mm and weighing just 25 g, the EH module is sufficiently compact to be attached in the boundary areas between existing tires and wheels. The module generates electricity every time the tire rotates, with an average continuous output of 1 mW when the car is traveling in a straight path at 105 km/h (about 65 mph).

This amount of power generation is sufficient to enable sensing, analysis with a low-power microcontroller, and wireless transmission. The power source is also scalable. Installing multiple EH modules in a tire will generate more power, enabling more detailed monitoring of vehicular data. In other words, it offers the ability to power even more sensors, like accelerometers in addition to temperature sensors and pneumatic pressure sensors, with data transmitted to the vehicle wirelessly.

Thanks to the EH module, InWheelSense can deliver real-time data analytics and information obtained directly from the tires/wheels wirelessly to the vehicle/driver and/or the cloud. Its energy harvesting and powerful processing capabilities enable the gathering of data and product analytics such as tire pressure, temperature, tread wear, tire load, traction forces, slip angle, predictive traction loss, infrastructure, and road condition information without the need for battery replacement.

These features provide added value to fleet management and improve driver/ vehicle analytics; as well as delivering accurate information at high communications rates for enhancing sensor-system development.


New horizons

The rapid evolution of different automotive sensor technologies to monitor for compliance, safety, and performance has been aided by parallel advancements in other sectors. New, advanced materials and miniaturization have enabled the development of suitably small, lightweight, and robust components. This means that multiple sensors can be applied to monitor virtually any aspect of a vehicle’s performance without dramatically increasing the payload.

The ability to embed intelligence, to use the data from multiple sensors in combination, is critical for delivering mobility as a service and for autonomous vehicles. To fully support the transition, TDK and others are applying their expert knowledge to address these issues and develop energy-efficient subsystems that will support future automotive development.

Subsystem and sensor innovations, which enable big data collection and analysis, need not be limited to consumer vehicle applications in the future. Our entire transportation network, from trains to ships and aircraft, would benefit from greater levels of functionality—making travel safer, more efficient, and more sustainable.

 

This article was written for Futurride by Dr. Peter G. Hartwell, Chief Technology Officer and VP of Sensor Solutions at TDK. He has over 25 years of experience commercializing silicon MEMS products, is responsible for technology strategy, and leads the company’s Advanced Technology research group.