This paper establishes a bias contribution model for a micromachined Coriolis vibratory gyroscope (MCVG). Eight bias sources, including stiffness imbalance, mass imbalance, and oscillation of the sense mode itself with their contributions, were analyzed and calculated. The calculation methods for key parameters, such as coupling stiffness, coupling damping, and offsets of center of mass based on the established process imperfection model, are presented in detail. Finally, the total bias of the MCVG is measured with an error of 18% compared with the theoretically calculated bias using the model. The acceptable error range of the bias model provides a solution to predict the bias behavior in the design stage before the costly fabrication.

Bias accuracy of micromachined gyroscope is deteriorated severely when suffering from unknown environmental disturbances (UD), such as temperature, vibration, and shock. In this article, gyros array using a two-stages UD-decoupled fusion strategy is for the first time proposed to maintain high-accuracy bias under unknown disturbances. In detail, the evolvement model of the individual gyroscope among four-gyros array is first deduced to decouple UD. Then, local estimator is devised to simultaneously derive the estimates of the state, the bias, and the UD of each gyro among the array in the first stage, respectively. Further, due to the nonoptimal local state estimates caused by the inherent response difference between each gyro, the global state fusion estimator weighted by dynamic coefficients is devised to achieve the uniformly optimal state estimate of gyros array in the second stage. The experimental test shows that RMSE of the estimate based on the proposed method is evaluated as 0.13°/s, which is reduced by 92.4%, 87%, 82.4%, and 51.9% compared with kalman filter (KF), internal model approach (IMA), distributed optimal linear fusion estimator (DOLFE), and minimal learning parameter-neural network (MLP-NN), respectively. The tested scale factor of the array is calibrated as 5.9 mv/°/s and the corresponding bias stability is calculated as 0.019°/s, which is improved by 68.8%, 54.8%, 34.5%, and 17.4% compared with KF, IMA, DOLFE, and MLP-NN, respectively. Not only is bias accuracy under UD not deteriorated, on the contrary, the accuracy is improved significantly by 3.7 times compared with that without UD. The proposed array-based UD-decoupled method paves an effective path to apply microgyro in actual environment engineering.

MEMS fabrication that is based on the silicon-on-glass (SOG) process requires many steps, including patterning, anodic bonding, deep reactive ion etching (DRIE), and chemical mechanical polishing (CMP). The effects of the process parameters of CMP and DRIE are investigated in this study. The process parameters of CMP, such as abrasive size, load pressure, and pH value of SF1 solution are examined to optimize the total thickness variation in the structure and the surface quality. The ratio of etching and passivation cycle time and the process pressure are also adjusted to achieve satisfactory performance during DRIE. The process is optimized to avoid neither the notching nor lag effects on the fabricated silicon structures. For demonstrating the capability of the modified CMP and DRIE processes, a z-axis micro gyroscope is fabricated that is based on the SOG process. Initial test results show that the average surface roughness of silicon is below 1.13 nm and the thickness of the silicon is measured to be 50 μm. All of the structures are well defined without the footing effect by the use of the modified DRIE process. The initial performance test results of the resonant frequency for the drive and sense modes are 4.048 and 4.076 kHz, respectively. The demands for this kind of SOG MEMS device can be fulfilled using the optimized process.

We propose and numerically investigate a brand-new, high-sensitivity progressive wave gyroscope based on acousto-optic effects for the measurement of rotational angular velocity. Unlike the traditional surface acoustic wave (SAW) gyroscope, which uses shifts in the SAW frequency to characterize the rotational angular velocity, this study uses acousto-optic effects to detect changes in refractive index caused by mechanical strain, measuring the angular velocity by the output optical power intensity of the optical waveguide. The three-dimensional finite element analysis method is utilized to build an SAW excitation model and optical detection model. We show that the sensitivity of the SAW gyroscope is highly dependent upon geometric parameters of the structure and that the mechanical strain induced by the progressive wave of the SAW can be effectively measured by the optical power intensity under the action of external angular velocity. The superiority of the proposed structure is substantiated by its achievement of a theoretical sensitivity of 1.8647 (mW/m²)/(rad/s) and high impact resistance of 220,000 g. By means of normalization, the sensitivity of the proposed structure can be enhanced by four orders of magnitude compared to the traditional SAW gyroscope. The novel structure combines the advantages of both conventional microscale vibrating gyroscopes and optical gyroscopes, providing a powerful solution for performance enhancement of SAW gyroscopes and, thereby, enabling application in the field of inertial devices.