A Three-Dimensional Finite Element Analysis Model for SH-SAW Torque Sensors

Abstract

In this paper, a three-dimensional finite element analysis (3D-FEA) model for shear horizontal surface acoustic wave (SH-SAW) torque sensors is presented. Torque sensors play a significant role in various fields to ensure a reliable torque transmission in drivelines. Featured with the advantages of high propagation velocity, large Q-value, and good power capacity, SH-SAW based torque sensors are promising but very few studies have been carried out. In order to develop a successful sensor, understanding the characteristics of SH-SAWs produced on piezoelectric substrates and torque sensing modes is indispensable. Therefore, in this study, we first investigated the effect on the generation of waves when different Y-cut quartz substrates are engaged. Thereafter, analyses and comparisons, regarding the effect on the polarized displacement, wave guidance, and wave mode, were conducted for different configurations of wave-guide layer thickness to wavelength ratios (hlayer/λ) and materials. Results show that Y-cut quartz at an angle close to 36° with a gold (Au) layer varying from hAu/λ = 0.02 to 0.03 thickness could be the most effective configuration for the excitation of SH-SAWs, compared to other combinations using platinum (Pt), titanium (Ti) and silicon dioxide (SiO2). Finally, based on the FEA SH-SAW torque sensor model configuring with a Y+36° quartz substrate and 0.025 λ-thick gold layer, the relationship between the applied torque and sensed voltage was examined, which shows a perfect linearity demonstrating the performance of the sensors.