Wireless Tyre Sensors Based on Amorphous Magneto-Elastic Materials

Abstract

Nowadays customised sensors and actuators are very important in order to optimise and control process parameters of engines, machines and other moving parts. Wireless interrogation of the sensors is necessary in order to gain information from hidden spots within the engine or from rotating shafts, axles or car tyres. Therefore we have exploited the possibility of using magneto-elastic wires as sensor elements to monitor the frictional conditions between the tyre and the roadway in order to enhance the active vehicle safety. In vehicles having wheels with rubber tyres, the deformation and forces that occur in the tyre material provide information about the driving status of the vehicle. Especially, it is possible to monitor current frictional conditions between the tyre and the roadway.

Magneto-elastic wires are extremely sensible to small changes of applied mechanical stresses due to the inverse magnetostrictive effect. Figure 1 shows a typical change of the hysteresis loop of a magneto-elastic wire and the differential permeability, correspondingly. The change of the material permeability μ is directly correlated with a change in the skin depth δ and therefore with a change of the impedance Z of the material (GMI effect).