TDK’s InWheelSense Showcases the Future Automobile Sensor Systems

Cars today are littered with electronics, to the point where more than 30% of the cost of a vehicle is from the electronic systems alone. These systems give us touch screen displays, radio, automatic braking systems, and sensors that provide information such as fuel level, distance travelled, miles per gallon, speed/acceleration, when your next oil change is needed, engine temperature and RPM, and tire pressure. 

TDK’s InWheelSense^TM solution aims to help with tire pressure monitoring as well as other tire properties as it is being released as an industry leading Tire Pressure Monitoring System (TPMS). These TPMS’s along with the self-inflating tire systems used in the military and a few high end vehicles, are the only systems utilized widespread in the tire-wheel area according to TDK’s press release.

 

IWCM mother board with sensors. Image courtesy of TDK.

 

The InWheelSenseTM is a powerful and autonomous sensor system with robust capabilities. Consisting of three main sections, power, sensing and connectivity, the platform, connected directly to the vehicle’s wheel, delivers data analytics either directly to the car or to devices connected via the cloud. 

The power block contains a piezoelectric electric, made of lead zirconate titanate (PZT) material. Utilizing the direct piezoelectric effect, where a mechanical force generates an electrical charge. Specifically, one single energy harvesting (EH) module if implemented on an 18” diameter wheel and the vehicle is moving at 65 mph, will generate a 1 mW of power. Scalability of modules is allowed as well if higher power is needed. 

This power module can be used to either charge a lithium ion battery for long term usage, or a supercapacitor for shorter bursts of energy. The shorter bursts of energy option, also known as the “burst mode” for the module, can supply up to 18 mW for 30 msec, and is very helpful in sensor applications that spend the majority of its time in sleep mode, and wake up intermittently to measure from sensors and send out data. The EH module is currently patent pending. The EH module feeds into an on-board power management integrated circuit (PMIC) that converts that AC voltage into a steady, ripple-free regulated 3.3 V DC supply.

In terms of actual sensors, the InWheelSenseTM module contains the following standard sensors:

• Multi-channel High Sensitivity InWheelSense™ EH sensor
• 6-Axis inertial measurement unit (IMU)
• Barometric Pressure sensor
• Temperature sensor
• Future development activities include:
• 9-Axis IMU
• 2 channel Microphone
• Ultrasonic Time of Flight (TOF)
• Hall effect switch
• Shock/Wake sensor (EH sense)
• Brake dust, tire micro plastic particle sensor

The EH sensors have the same anatomy as the power module and the power module itself can be used as another sensor if the user decides to do that for similar purposes to the standard EH sensors. Additional sensors can also be added to increase functionality. The sensors can sense metrics both on and off the wheel, where off-wheel metrics include car door closures and gear engagement to name a few.

 

TDK’s InWheelSense™ EH Module. Image courtesy of TDK.

 

Lastly, the module currently has one method of connectivity to either a host computer or processing device, which is low energy Bluetooth (BLE). This connectivity allows continuous real-time data streaming, and processed data can be utilized for dashboard-like displays, showing warning and indicator lights based on any measured values of concern. In the future, the system plans to implement a low-power wide-area network (LPWAN) protocol. This will allow communication for long distances (up to 10 km), and the protocol is ideal for low power, battery operated devices. Finally, a “black box” is a future enhancement on board that will be a memory module for data recording capabilities.

The InWheelSenseTM module is a great innovation that will allow for simple, efficient and powerful tire sensing. This will help for applications such as road surface condition, slip detection, tread wear, pothole mapping and loose wheel indication among others. This module will improve the automotive industry no matter where it goes, whether it is used in current technology, EVs, or autonomous vehicles.