Yongmeng Zhang

Structural-Acoustic Coupling Effects on the Non-Vacuum Packaging Vibratory Cylinder Gyroscope

The resonant shells of vibratory cylinder gyroscopes are commonly packaged in metallic caps. In order to lower the production cost, a portion of vibratory cylinder gyroscopes do not employ vacuum packaging. However, under non-vacuum packaging conditions there can be internal acoustic noise leading to considerable acoustic pressure which is exerted on the resonant shell. Based on the theory of the structural-acoustic coupling, the dynamical behavior of the resonant shell under acoustic pressure is presented in this paper. A finite element (FE) model is introduced to quantitatively analyze the effect of the structural-acoustic coupling. Several main factors, such as sealing cap sizes and degree of vacuum which directly affect the vibration of the resonant shell, are studied. The results indicate that the vibration amplitude and the operating frequency of the resonant shell will be changed when the effect of structural-acoustic coupling is taken into account. In addition, an experiment was set up to study the effect of structural-acoustic coupling on the sensitivity of the gyroscope. A 32.4 mV/°/s increase of the scale factor and a 6.2 Hz variation of the operating frequency were observed when the radial gap size between the resonant shell and the sealing cap was changed from 0.5 mm to 20 mm.

A Novel Vibration Mode Testing Method for Cylindrical Resonators Based on Microphones

Non-contact testing is an important method for the study of the vibrating characteristic of cylindrical resonators. For the vibratory cylinder gyroscope excited by piezo-electric electrodes, mode testing of the cylindrical resonator is difficult. In this paper, a novel vibration testing method for cylindrical resonators is proposed. This method uses a MEMS microphone, which has the characteristics of small size and accurate directivity, to measure the vibration of the cylindrical resonator. A testing system was established, then the system was used to measure the vibration mode of the resonator. The experimental results show that the orientation resolution of the node of the vibration mode is better than 0.1°. This method also has the advantages of low cost and easy operation. It can be used in vibration testing and provide accurate results, which is important for the study of the vibration mode and thermal stability of vibratory cylindrical gyroscopes.

Modeling and analysis of mechanical Quality factor of the resonator for cylinder vibratory gyroscope

Mechanical Quality factor(Q factor) of the resonator is an important parameter for the cylinder vibratory gyroscope(CVG). Traditional analytical methods mainly focus on a partial energy loss during the vibration process of the CVG resonator, thus are not accurate for the mechanical Q factor prediction. Therefore an integrated model including air damping loss, surface defect loss, support loss, thermoelastic damping loss and internal friction loss is proposed to obtain the mechanical Q factor of the CVG resonator. Based on structural dynamics and energy dissipation analysis, the contribution of each energy loss to the total mechanical Q factor is quantificationally analyzed. For the resonator with radius ranging from 10 mm to 20 mm, its mechanical Q factor is mainly related to the support loss, thermoelastic damping loss and internal friction loss, which are fundamentally determined by the geometric sizes and material properties of the resonator. In addition, resonators made of alloy 3J53 (Ni42CrTiAl), with different sizes, were experimentally fabricated to test the mechanical Q factor. The theoretical model is well verified by the experimental data, thus provides an effective theoretical method to design and predict the mechanical Q factor of the CVG resonator.

A Simple Acoustic Method for Modal Parameter Measurement of the Resonator for Vibratory Shell Gyroscope

In this paper, an acoustic method measuring the frequency split, quality factor and modal deflection of the resonator for vibratory shell gyroscope (VSG) is presented. This method is based on the superposition and decomposition of acoustic waves generated by standing wave eigenmodes of the resonator. The acoustic signals from an imperfect resonator comprise two standing waves of different frequencies and orientations. Theoretical study shows that the oscillating period and trough-peak ratio of the composite acoustic wave are strongly related to the modal parameters of the resonator. Therefore, the modal parameters of the resonator can be obtained via parameter fitting of the acoustic signal. The measurement error due to vibration drift is also analyzed in the theoretical study. The proposed method could be a simple and fast way to measure the main modal parameters of the VSG resonators without using sophisticated or costly equipments. Experiments were implemented to identify the modal parameters of a typical cylindrical resonator using the acoustic method. For the sake of comparison, traditional electrical and optical methods were also employed to measure the modal parameters. The experimental results show that the modal parameters measured by the acoustic method are close to those obtained from the traditional methods.

Analysis on Node Position of Imperfect Resonators for Cylindrical Shell Gyroscopes

For cylindrical shell gyroscopes, node position of their operating eigenmodes has an important influence on the gyroscopes’ performance. It is considered that the nodes are equally separated from each other by 90° when the resonator vibrates in the standing wave eigenmode. However, we found that, due to manufacturing errors and trimming, the nodes may not be equally distributed. This paper mainly analyzes the influences of unbalanced masses on the cylindrical resonators’ node position, by using FEM simulation and experimental measurement.

0.04 degree-per-hour MEMS disk resonator gyroscope with high-quality factor (510 k) and long decaying time constant (74.9 s)

The disk resonator gyroscope is an attractive candidate for high-performance MEMS gyroscopes. This gyroscope consists of a sensor and readout electronics, and the characteristics of the sensor directly determine the performance. For the sensor, a high-quality factor and long decaying time constant are the most important characteristics required to achieve high performance. We report a disk resonator gyroscope with a measured quality factor of 510 k and decaying time constant of 74.9 s, which is a record for MEMS silicon disk resonator gyroscopes, to the best of our knowledge. To improve the quality factor of the DRG, the quality factor improvement mechanism is first analyzed, and based on this mechanism two stiffness-mass decoupled methods, i.e., spoke length distribution optimization and lumped mass configuration design, are proposed and demonstrated. A disk resonator gyroscope prototype is fabricated based on these design strategies, and the sensor itself shows an angle random walk as low as 0.001°/√h, demonstrating true potential to achieve navigation-grade performance. The gyroscope with readout electronics shows an angle random walk of 0.01°/√h and a bias instability of 0.04°/h at room temperature without compensation, revealing that the performance of the gyroscope is severely limited by the readout electronics, which should be further improved. We expect that the quality factor improvement methods can be used in the design of other MEMS gyroscopes and that the newly designed DRG can be further improved to achieve navigation-grade performances for high-end industrial, transportation, aerospace, and automotive applications.MEMS: high-quality factor sensors for resonator gyroscopesA disk resonator gyroscope demonstrates a high-quality factor of 510 k and decay time constant of 74.9 s. High-performance MEMS gyroscopes are in demand for a range of high-end applications. Disk resonator gyroscopes are particularly promising candidates due to inherent mode matching and high thermal stability. However, many applications demand high-quality factors and long decay times. Now, a team led by Xuezhong Wu at the National University of Defense Technology, China, reports what they claim are record quality factors and decay times for MEMS silicon disk gyroscopes. Two mechanisms for stiffness-mass decoupling are attributed to the high performance, which the authors say could be used for the design of other MEMS gyroscopes.

Research on cylindrical resonators’ damping asymmetry trimming method utilizing damping characteristic of piezoelectric electrodes

The damping asymmetry of cylindrical resonators is one of the major sources which result in the gyroscope’s drift. In this paper, a new approach for trimming the damping asymmetry of cylindrical resonators is proposed. The damping asymmetry trimming model is established to analyze the additional damping’s influences. Furthermore, piezoelectric electrodes’ effects on the cylindrical resonator’s damping characteristic are figured out through the finite element simulation. The procedures of this trimming method are also summarized based on theoretical analysis. At last, these theoretical analysis and simulation results are utilized to compensate the damping asymmetry of cylindrical resonators and the procedures of this trimming method are also summarized. Experiments are also implemented to verify this trimming method.

Analysis of the Damping Characteristics of Cylindrical Resonators Influenced by Piezoelectric Electrodes

The cylindrical resonator gyroscope (CRG) is a typical Coriolis vibratory gyroscope whose performance is mostly influenced by the damping characteristic of the cylindrical resonator. However, the tremendous damping influences caused by pasting piezoelectric electrodes on the gyroscope, which degrades the performance to a large extent, have rarely been studied. In this paper, the dynamical model is established to analyze various forms of energy consumption. In addition, a FE COMSOL model is also created to discuss the damping influences of several significant parameters of the adhesive layer and piezoelectric electrodes, respectively, and then explicit influence laws are obtained. Simulation results demonstrate that the adhesive layer has some impact on the damping characteristic, but it not significant. The Q factor decreases about 30.31% in total as a result of pasting piezoelectric electrodes. What is more, it is discovered that piezoelectric electrodes with short length, locations away from the outside edges, proper width and well-chosen thickness are able to reduce the damping influences to a large extent. Afterwards, experiments of testing the Q factor are set up to validate the simulation values.

Nonlinear vibration and its influence on the vibratory cylinder gyroscope

Vibratory cylinder gyroscope (VCG) is an important type of vibratory gyroscopes with a lot of advantages. Manufacturing errors and material inhomogeneity are regarded as the main cause of the zero bias drift of the VCG. In this paper, the nonlinear vibration of the cylindrical resonator is considered. It is analyzed that the nonlinear vibration can cause extra drift of the VCGs output. Experiments are implemented in this research. According to the testing results, the metal cylindrical resonator is a soft nonlinear vibration system. To increase the stability of the VCG, the cylindrical resonator should be trimmed to a specific frequency split. This electronic document is a “live” template and already defines the components of your paper [title, text, heads, etc.] in its style sheet.