Wireless physical SAW sensors for automotive applications

The paper gives an overview of the early research projects devoted to pressure and torque automotive sensors based both on SAW reflective delay lines and resonators. Motivation behind development of the automotive SAW sensors and their advantages and disadvantages in comparison with competing technologies are discussed. Further progress of the automotive SAW sensors from the first demonstrators to production-ready systems required development of an inexpensive and accurate wireless interrogator, compact SAW sensing elements, packages for them and calibration methods suitable for high volume manufacturing. The paper discusses evolution of the sensing elements and interrogation methods with a particular emphasis on the resonant SAW sensors. A number of SAW sensing systems recently developed for automotive applications is presented: the tire pressure and temperature monitoring systems (TPMS) for sports cars and off-the-road vehicles, the torque and temperature sensor for the electrical power assisted steering system, the flexplate sensor for measuring engine output torque, and the torque sensor for the F1 kinetic energy recovery system (KERS).