Search

This article presents a novel self-calibration method to improve the scale factor (SF) stability by the synchronous control on the first-order and third-order harmonic components of nonlinear detection. On the conventional scheme of a drive loop, the readout amplitude of the first-order harmonic component is controlled at a constant value. However, the actual vibration amplitude of drive-mode motion would drift due to the change of circuit gains between the readout amplitude and actual amplitude, thereby resulting in the deterioration of the SF stability. The third-order harmonic component of nonlinear detection shares the same circuit with the vibration signal, indicating that its readout amplitude can track the change in circuit gains in real time. Therefore, this new approach replaces the original fixed reference with the varying readout amplitude of the third-order harmonic component to eliminate the drive-mode vibration error and eventually calibrate the drift of SF. Experiments performed on a honeycomb disk resonator gyroscope (HDRG) have demonstrated the feasibility of the calibration method. The calibration based on the harmonic extraction yields a short-term SF repeatability of 24.9 ppm and a long-term SF repeatability of 30.8 ppm. Allan deviation analysis of the calibrated SF demonstrates a 3.5-ppm precision upon an average of 200 s. The temperature sensitivity of the SF is reduced from 717.3 ppm/°C to 5.02 ppm/°C and the SF repeatability is improved from 15643 ppm to 94.9 ppm over the temperature range of −30 °C to 30 °C. [ABSTRACT FROM AUTHOR]

Micro hemispherical resonator shows great potential for applications in high-performance gyroscopes. This paper introduces micro hemispherical resonator with teeth-like tines along the edge, aiming at improving mechanical sensitivity of the gyroscope and simplifying the mechanical trimming. The optimized glassblowing resonators with substrate thickness of 200 μm and height near 4.5 mm shows high quality factor, large sensitivity, and balanced electrode gaps. The n = 2 wineglass modes operate at 4.3 kHz, achieving quality factor of 1.18 million and as-fabricated frequency split of 17.8 Hz. After mechanical trimming, the frequency split is reduced below 70 mHz. The vacuum-packaged micro hemispherical resonator gyroscope (mHRG) operating in force-rebalance mode exhibits full-scale range of ±200 deg/sec and bias instability of 0.133 deg/h at room temperature without compensation, indicating that the performance of the gyroscope is limited by the readout electronics. Further improvement is in progress to achieve navigation-grade performance with rate-integrating operation. [ABSTRACT FROM AUTHOR]

Micro glassblowing can be utilized in the fabrication of high-precision micro shell resonator due to its acceptable cost and promising performance. Geometric imperfection characterization and electrode assembly are important but challenging tasks for manufacturing high-quality resonators. This paper characterizes the geometric imperfection of the micro shell resonator and proposes a novel precise assembly process for micro shell resonators with out-of-plane electrodes. The crucial geometric imperfections including thickness imperfection, circularity error and anchor non-planarity of the glassblowing structures are experimentally characterized. The sample resonator exhibits a circularity error below 0.2 % and an anchor non-planarity of 300 nm. The relationship between frequency asymmetry and circularity error is discussed, which can be used to predict the resonator performance. A simplified model is built to analyze the effect of gap deviation on the capacitance variation of the resonator. Finally, a sacrificial layer-free electrode assembly method is proposed, which achieves small ($< 20~\mu \text{m}$) capacitance gaps with relatively low tolerance. [2019-0235] [ABSTRACT FROM AUTHOR]

A novel micro shell resonator gyroscope (MSRG) with 16 T-shape masses using out-of-plane electrodes is proposed in this paper. The T-shape masses are designed for high transduction efficiency. Out-of-plane electrodes are used to drive and detect the spatial deformation of the resonator. The finite element method (FEM) is applied to evaluate the influence of the T-shape mass on transduction efficiency. Compared with the MSRG without the T-shape masses, the FEM results reveal that the MSRG with T-shape masses has shown an increase of 42% on effective mass (${M}_{ {eff}}$) and a decrease of 8% on ${f}_{ {n=2}}$. For the MSRG without T-shape mass, spherical–cylindrical, spherical, and out-of-plane electrodes have been applied to drive and sense n = 2 wineglass modes. Compared with the MSRG without T-shape using out-of-plane electrodes, the MSRG with T-shape masses has showed the improvement of 334%, 522%, and 598% on driving efficiency (${S}_{ {d}}$), detection efficiency (${S}_{ {s}}$), and mechanical sensitivity (${S}_{ {mech}}$) due to large ${M}_{\text {eff}}$ and electrode area. In addition, the improvement of 15% in the thermal noise of a gyroscope (ARW $_{\text {mech}}$) is dominated by a large effective mass, contributing to the improvement of signal-to-noise ratio. The process of micro blow torching with the whirling platform and femtosecond ablation is presented to fabricate the MSRG with T-shape masses. The performance of MSRG is demonstrated experimentally with out-of-plane capacitive transduction. The MSRG is operated in the force-rebalance mode, which demonstrates a scale factor of 0.107V/(°/s), an angle random walk of 0.099°/ $\text{h}^{{1/2}}$ , and a bias instability of 0.46°/h, showing a great potential for high-performance gyroscopic application. [ABSTRACT FROM AUTHOR]

This paper presents a novel micro shell resonator (MSR) with T-shape masses based on fused silica using out-of-plane electrode structures. Eight circular-distributed T-shape masses are designed along the rim of resonator shell to improve transduction efficiency, including drive efficiency and detection efficiency. The dynamic parameters and transduction efficiency are calculated and optimized with finite element method, revealing 3.76 times improvement in drive efficiency, 4.65 times improvement in detection efficiency, and 17.81 times increase in mechanical sensitivity. In addition, it is feasible to trim the frequency by adding or removing mass on the T-shape masses. The key feature of the process is based on micro blow-torching process and whirling platform, which form the resonator structure with smooth roughness and good structure uniformity. Femtosecond laser ablation is used to release the T-shape masses for good symmetry and high processing quality. Then, metalized MSR with T-shape masses is assembled on a glass substrate. Electrostatic transduction is used to detect spatial deformation of resonators by out-of-plane electrodes, which reveals a frequency mismatch of 0.175% at 6904.4 Hz and 6916.5 Hz with quality factors of 20.39 k ( $\tau =0.94$ s) and Q = 36.94$ k ( \tau =1.7\text{s} ). [2017-0086] [ABSTRACT FROM PUBLISHER]

This paper reports a new design strategy of adding lumped masses to the frame structure of a disk resonator gyroscope (DRG) to mitigate its figure of merit (FOM). A greatly enhanced decaying time constant τ can lead to very small FOM, which could then greatly mitigate the DRG's bias and bias drift. Additionally, this technique could also reduce the Brownian noise floor. A comprehensive investigation of the possible ways to add the lumped masses is presented, and a detailed design guideline is provided. A DRG prototype based on this design strategy is then presented and shows a τ of 38.5 s, a quality factor Q of 358 k, and a FOM of 1.9°/s. The prototype is operated in the force-to-rebalance mode, and an angle random walk of 0.012°/√h and a bias stability of 0.08°/h are demonstrated experimentally. This design strategy is suitable for use in batch fabrication of very high precision microelectromechanical systems devices such as gyroscopes. [ABSTRACT FROM PUBLISHER]

In this paper, we present the mechanical sensitivity improvement of a disk resonator gyroscope (DRG) by optimizing the thickness distribution of the nested rings. The mechanical sensitivities of the DRGs with uniform, linearly changing, and step changing rings have been simulated. The results suggest that the ring thickness distribution has great influence on the performance of the DRG. Then, the optimized ring thickness distribution was obtained by using the traditional method of moving asymptotes (MMA), which result in a 24% improvement of the mechanical sensitivity. Finally, the bio-inspired particle swarm optimization (PSO) algorithm has also been used. The optimization results of PSO coincide well with that of MMA, and the optimized result is the global optimum. Meanwhile, the optimized distribution rules can be used on the series of DRGs and the optimization methods can be widely used on other microelectromechanical systems (MEMS) devices. [2015-0310] [ABSTRACT FROM PUBLISHER]