Experiments on structural-acoustic coupling were conducted as well by some researchers. It was reported that a finite thin cylindrical shell was excited by an internal acoustic source, and the pressure field of the shell could be measured using laser measurements [14]. Some other researchers investigated the structural-acoustic mode of the cylindrical duct, which was used for the geometrical shape design of a cavity device [15]. The effects of structural-acoustic coupling are of concern in the areas of vibration analysis, structural design and optimization, etc. [16]. In the field of Coriolis vibratory gyroscopes, studies on the structural-acoustic coupling effect are relatively scarce.

Reference [17] shows that if the acoustic energy frequency components are close to the eigenfrequency of the mechanical structure in the MEMS gyroscope, undesirable motion of the sensor proof mass resulting in signal corruption can be produced. In [18,19] it is revealed that the performance of a vibratory cylinder gyroscope may also suffer from intense acoustic noises. However, little quantitative data or analysis has been presented. Most efforts to improve the gyroscope performance have concentrated on the vibratory structural elements, such as material processing, structural optimization and evolution. [2,4,7,20]. It is easily known that the vibration amplitude of the thin resonant shell is highly sensitive to the pressure exerted on its surface, and the resonant frequency of the resonant shell can be affected as well.

Therefore, the performance of the vibratory cylinder gyroscopes will be uncertain when the structural-acoustic coupling effect is taken into account.In this paper, the structural-acoustic coupling effect on a type of low cost vibratory cylinder gyroscope without vacuum packaging is studied. The dynamical behavior of the resonant shell is analyzed in theory. In addition, the coupling effects are quantitatively analyzed based on FE simulation. It is found that the operating frequency, the acoustic pressure and the vibration amplitude of AV-951 the resonant shell are changed due to the gap variation between the resonant shell and the sealing cap. The degree of vacuum is also changed to observe the fluctuation of the shell vibration. Finally, experiments were implemented to study the mechanical sensitivity (scale factor) of the gyroscope which could be affected by the structural-acoustic coupling effect.

The simulation and experimental results are useful for a deeper understanding of the performance of the vibratory cylinder gyroscopes without vacuum packaging.2.?Gyroscope DescriptionThe typical vibratory cylinder gyroscope analyzed in this paper is shown in Figure 1. The physical part of the gyroscope is mainly made up by a resonant shell, a sealing cap and a base. The resonant shell is fabricated with nickel alloy such as Ni42CrTi and Ni-SPAN-C Alloy 902 [2].