Abstract
A new micro gyroscope based on the surface acoustic wave (SAW) gyroscopic effect was developed. The SAW gyroscopic effect is investigated by applying the surface effective permittivity method in the regime of small ratios of the rotation velocity and the frequency of the SAW. The theoretical analysis indicates that the larger velocity shift was observed from the rotated X-112°Y LiTaO3 substrate. Then, two SAW delay lines with reverse direction and an operation frequency of 160 MHz are fabricated on a same X-112°Y LiTaO3 chip as the feedback of two SAW oscillators, which act as the sensor element. The single-phase unidirectional transducer (SPUDT) and combed transducers were used to structure the delay lines to improve the frequency stability of the oscillator. The rotation of a piezoelectric medium gives rise to a shift of the propagation velocity of SAW due to the Coriolis force, resulting in the frequency shift of the SAW device, and hence, the evaluation of the sensor performance. Meanwhile, the differential structure was performed to double the sensitivity and compensate for the temperature effects. Using a precise rate table, the performance of the fabricated SAW gyroscope was evaluated experimentally. A sensitivity of 1.332 Hz deg−1 s at angular rates of up to 1,000 deg s−1 and good linearity are observed.
Highlights
The surface acoustic wave (SAW) based gyroscope has provided a new method for angular rate detection with excellent inherent shock robustness, very larger dynamic testing range, small size, low cost, simplicity and long working life [1]
A typical SAW gyroscope consists of a two-port SAW resonator to generate a stable standing wave and a SAW delay line pattern to detect the second SAW induced by Coriolis force acting on the metallic masses distributed along the anti-node position of the standing wave
The second aim of this study is to develop a valuable SAW gyroscope based on an X-112°Y
Summary
The surface acoustic wave (SAW) based gyroscope has provided a new method for angular rate detection with excellent inherent shock robustness, very larger dynamic testing range, small size, low cost, simplicity and long working life [1]. Some groups have reported such SAW-based gyroscopes with different designs and structures. Jose et al first reported a successful SAW gyroscope configuration based on a standing-wave mode with a voltage sensitivity of 2.67 mV s deg−1 [2]. Varadan et al presented the design and performance evaluation of a 74.2 MHz microelectromechanical system-interdigital transducer (MEMS-IDT) SAW gyroscope with a similar structure [3]. Zhang and Wang present an optimal design of the SAW device using the coupling of modes, considering the effect of metallic dot thickness on sensor performance [4]. Despite some reported important works on such SAW gyroscopes, they still suffer from low precision (submicron voltage detection) and poor temperature stability due to the use of large piezoelectric-coupling substrate materials like LiNbO3 with high temperature coefficients
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