A passive wireless surface acoustic wave sensor for pillar load measurement

Abstract

This paper presents a passive wireless pillar load measurement method based on surface acoustic wave (SAW) technology. A strain transfer mechanical structure was designed, and the strain distribution of an elastic substrate was analyzed using elastic thin plate bending theory. In addition, the relationship between the strain and frequency shift of the SAW resonator (SAWR) was analyzed, and a strain sensitivity numerical analysis using different bonding directions was performed. Results corroborated that the differential structure of resonators, one of which is placed at the edge along the direction of a diameter and the other is placed at the center with an angle of 45° to the diameter, is a suitable form of the SAW load sensors. Moreover, the SAWR parameters were optimized to obtain a high-performance resonator. Furthermore, The SAWRs and strain transfer mechanical structures were manufactured, the pillar load measurement system was set, and the proposed SAW load measurement method was evaluated. Experimental results affirmed that the load sensitivity is 8.64 kHz/kN. The SAW pillar load method is feasible for practical application.