Gyroscope Prototype Research Articles

Monolithic Fully Decoupled Tri-Axis Gyroscope With Lateral-Comb and Low Cross-Coupling

Multi-axis integration is important for micro-electromechanical system(MEMS) gyroscopes in the future. In this paper, a monolithic integrated tri-axis gyroscope and interface circuit are designed and implemented. The presented tri-axis gyroscope with single drive and multi sense axes is fully decoupled in structure among the drive and sense modes. Quadrature coupling can also be further reduced by the in-plane and out-of-plane correction electrodes. The pitch(roll) structure is designed as a unilateral unequal height comb, which reduces the damping and improves the Q value of pitch and roll modes and simplifies the fabrication process. In addition, the interface circuit adopts a closed-loop drive and open-loop sense circuit, an additional decoupling module that effectively reduces the cross axis sensitivity. Finally, a gyroscope prototype was tested to evaluate its performance. The designed tri-axis gyroscope has low bias instability(1.2821°/h) and good noise performance(0.1635°/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd \text{h}$ </tex-math></inline-formula> ). The coupling coefficient is even below 1% after adding decoupling modules. Meanwhile, the bandwidth can meet the needs of the gyroscope working in a low-frequency environment.

Optimization and Fabrication of an MOEMS Gyroscope Based on a WGM Resonator.

In this paper, the characterization of a whispering gallery mode (WGM) resonator applied in a novel micro-opto-electro-mechanical system (MOEMS) gyroscope was investigated. The WGM optical transmission coupling model was analyzed and compared by adjusting key parameters, such as the cavity radius, the waveguide width, and the gap between them for silicon and silicon nitride materials in simulations, which will greatly affect the quality factor (Q) of the WGM resonator. Furthermore, the structural parameters of the disk resonant gyroscope were also optimized. Then, the fabrication process was optimized to overcome the difficulties in the realization of micro-optical devices. Finally, a gyroscope prototype with the integrated WGM resonator was verified experimentally. The scale factor and bias instability performance of the MOEMS gyroscope was 2.63 mv/°/s and 4.0339°/h, respectively.

Fiber-Optic Gyroscope Accuracy Improvement by Suppressing the Parasitic Effects in Integrated Optic Phase Modulators

The results of study of a fiber-optic gyroscope prototype with 0.01–0.001deg/h drift are presented. The gyroscope comprises three feedback loops: one for Sagnac phase difference compensation, the second one for the scale factor stabilization, and the third (fast-response) one for the compensation of constant component of optical signal on the photodetector, affecting the measurement channel. To increase the accuracy of the prototype gyroscope up to the level of 0.001 deg/h, it is proposed to use the fourth and the fifth feedback loops which will suppress the parasitic effects in the integrated optic phase modulators.

0.04 degree-per-hour MEMS disk resonator gyroscope with high-quality factor (510\u2009k) and long decaying time constant (74.9\u2009s)

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.

Crystalline Waveguides for Optical Gyroscopes

We demonstrate ultra low loss and ultra low scattering ring waveguide optical resonators made of calcium fluoride crystal and illustrate their usefulness in optical metrology. The resonators are fabricated from crystalline preforms by mechanical polishing and subsequent thermal annealing. The feasibility of long delay lines based on the crystalline waveguides of similar morphology is discussed. A proof of principle chip-scale model of a Raman laser gyroscope using a calcium fluoride ring optical waveguide microcavity pumped with a C-band diode laser is demonstrated. The high quality of the optical waveguides results in symmetric clockwise (cw) and counterclockwise (ccw) Raman emission in the cavity. The counter-propagating Raman emission is utilized to measure rotation revealing itself as a Sagnac-induced frequency shift. The relative instability of the cw and ccw laser emission does not exceed 1 Hz for 0.1–10 $^4$ second averaging time and the frequency noise of the signal is less than 0.8 Hz/Hz $^{\text{1/2}}$ enabling a 3.8-mm ring cavity gyroscope prototype with better than 100 deg/hr sensitivity. We argue that the measurement sensitivity can be improved by four orders of magnitude by optimization of the Raman laser configuration.

Study on phase noise induced by 1/f noise of the modulator drive circuit in high-sensitivity fiber optic gyroscope

Abstract The contribution of modulator drive circuit noise as a 1/f noise source to the output noise of the high-sensitivity interferometric fiber optic gyroscope (IFOG) was studied here. A noise model of closed-loop IFOG was built. By applying the simulated 1/f noise sequence into the model, a gyroscope output data series was acquired, and the corresponding power spectrum density (PSD) and the Allan variance curve were calculated to analyze the noise characteristic. The PSD curve was in the spectral shape of 1/f, which verifies that the modulator drive circuit induced a low frequency 1/f phase noise into the gyroscope. The random walk coefficient (RWC), a standard metric to characterize the noise performance of the IFOG, was calculated according to the Allan variance curve. Using an operational amplifier with an input 1/f noise of 520 nV/√Hz at 1 Hz, the RWC induced by this 1/f noise was 2 × 10−4°/√h, which accounts for 63% of the total RWC. To verify the correctness of the noise model we proposed, a high-sensitivity gyroscope prototype was built and tested. The simulated Allan variance curve gave a good rendition of the prototype actual measured curve. The error percentage between the simulated RWC and the measured value was less than 13%. According to the model, a noise reduction method is proposed and the effectiveness is verified by the experiment.

A three-axis atomic magnetometer for temperature-dependence measurements of fields in a magnetically shielded environment

High performance spin-exchange-relaxation-free (SERF) gyroscopes require stable and homogeneous magnetic fields. These fields are usually sensitive to temperature. In this paper, a three-axis atomic magnetometer to measure the temperature dependence of fields inside the magnetic shields for a SERF gyroscope prototype is constructed and tested. Based on a three-beam configuration, three-axis vector capability is obtained by a cross-modulation scheme of the magnetic field components along orthogonal axes and subsequent demodulation of the relevant probe signals. The relative temperature dependence of magnetic fields inside the prototype shields is measured to be –. The results are useful for estimating the necessary precision of temperature control in both a SERF gyroscope and its fundamental physics applications.

Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications.

This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be 1310 nm. The theoretical calculated values of threshold sensitivity and dynamic range for this prototype are 0.052 °/h and 101.38 dB (from ±1.164 × 10−5 °/s up to ±78.19 °/s), respectively. The Scale-Factor (SF) non-linearity for this model is 5.404% relative to full scale, this value being obtained from data simulation results.

Comparison of Three Automatic Mode-Matching Methods for Silicon Micro-Gyroscopes Based on Phase Characteristic

In this paper, we investigated the method of automatic matching of the resonant frequencies for the decoupled dual-mass $z$ -axis silicon micro-gyroscopes. The structure of the studied gyroscope is first presented, which features the tuning combs for adjusting the resonant frequency, suppressing the quadrature error, and applying the feedback force. According to the phase characteristic of oscillators, different automatic frequency tuning loops are then designed to match the resonant frequencies of the drive and detection modes. Theoretical analysis is made to display the operation principles. In addition, they are verified and optimized by numeric simulations using the Simulink tool in MATLAB. Finally, by means of Labview Field Programmable Gate Array (FPGA), a digital hardware tool, these loops are tested on a fabricated and packaged gyroscope prototype. By comparison, it is found that when the automatic matching method under the external force is combined with the quadrature nulling method and the Coriolis closed-loop detection, the gyroscope is able to operate under real-time mode matching with a stable and small frequency split below 1 Hz. The performance of the prototype using this tuning method is: 1) the scale factor is 10.91 mV/°/s; 2) the input range is ±120°/s with nonlinearity of 0.1%; and 3) the bandwidth is 32 Hz. The frequency split varies by about 0.15 Hz under the open-loop detection and about 0.26 Hz under the closed-loop detection when the environment temperature changes by 80 °C.

Design and optimization of a resonant output frequency gyroscope for robust sensitivity and bandwidth performance

This paper presents the architecture and optimization verification of a designed mode-mismatching gyroscope prototype made with fused silica in atmospheric pressure. The gyroscope prototype uses the decoupling frame and double-ended tuning fork (DETF) to achieve high sensitivity and quality factor. This structure can suppress residual quadrature error due to fabrication errors and imperfections. The angle rate-sensitive elements of the proposed gyroscope prototype with quasi-digital FM output are two DETF resonators resulting in differential implementation. We describe the principle of operation characterization of our micromechanical vibratory rate gyroscope based on resonant sensing of the Coriolis force and establish mathematical model called multi-parameters excitation system dynamics of Mathieu equation based on our previous work. We specify and quantify the impact functions of mechanical parameters on the properties of gyroscopes and identify sensitivity and limitation of sensitivity and bandwidth each other. A sample-based stochastic model is established to investigate the influence of different uncertain structure size on gyroscope performance. According to the uncertainty analysis, we modify the previous gyroscope structure, and then the parameters and structure of the improved third version gyroscope are obtained. This research can provide a reference for design and optimization of the structure size to improve robustness and performance of resonant angle rate sensor.

Analysis and Design of a 3rd Order Velocity-Controlled Closed-Loop for MEMS Vibratory Gyroscopes

The time-average method currently available is limited to analyzing the specific performance of the automatic gain control-proportional and integral (AGC-PI) based velocity-controlled closed-loop in a micro-electro-mechanical systems (MEMS) vibratory gyroscope, since it is hard to solve nonlinear functions in the time domain when the control loop reaches to 3rd order. In this paper, we propose a linearization design approach to overcome this limitation by establishing a 3rd order linear model of the control loop and transferring the analysis to the frequency domain. Order reduction is applied on the built linear model's transfer function by constructing a zero-pole doublet, and therefore mathematical expression of each control loop's performance specification is obtained. Then an optimization methodology is summarized, which reveals that a robust, stable and swift control loop can be achieved by carefully selecting the system parameters following a priority order. Closed-loop drive circuits are designed and implemented using 0.35 μm complementary metal oxide semiconductor (CMOS) process, and experiments carried out on a gyroscope prototype verify the optimization methodology that an optimized stability of the control loop can be achieved by constructing the zero-pole doublet, and disturbance rejection capability (D.R.C) of the control loop can be improved by increasing the integral term.

Design and System Level Simulation of Double-Mass Silicon Micro Gyroscope

The double-mass silicon micro gyroscope prototype, mechanical structure and working principle are introduced, which has high sesitivity. According to dynamic equations, the signal characteristics are analyzed and the mathematical models of scale factro and bias are established. Then the system level model is established on Simulink platform, including mechanical errors and electrostatic coupling errors and the performance are evaluated. Finally, five gyroscope prototypes are tested, and the performance parameters are as follows, the scale factor is 15.63~19.210mV/°/s, bias stability is 8.9~23.9°/h, bias repeatability is 7.5~19.4°/h.

Design of a LC-tuned magnetically suspended rotating gyroscope

A inductor-capacitor (LC) tuned magnetically suspended rotating gyroscope prototype is designed and analyzed. High permeability ferrite cores are used for providing suspension force, and the rotation system is designed using the switched reluctance motor (SRM) principle. According to the LC-tuned principle, magnetic suspension force expression has been derived. The electromagnetic properties of the gyroscope are simulated by the Ansoft Maxwell software. And our result is expected to be able to serve as a prototype of micro-electromechanical system (MEMS) magnetically suspended rotating gyroscope in future practical applications.

A Dual-Axis Liquid-Rate Microgyroscope Using Electro-Conjugate Fluid

The dual-axis liquid-rate gyroscope using Electro-Conjugate Fluid (ECF) proposed here follows a previously proposed single-axis liquid-rate gyroscope using ECF [1], a dielectric “smart fluid” generating a powerful jet flow (ECF jet) under a strong Direct-Current (DC) electric field. Although the proposed gyroscope’s sensing principle is based on that of a conventional gas rate sensor [2-4], the gyroscope itself is much more sensitivity because its density is generally higher than that of a gas. The gyroscope is more suitable for a microsensor than a gas rate sensor having a pump with piezoelectric actuator because the proposed gyroscope’s pump consists of a pair of tiny electrodes. We fabricated a 40×40×21 mm3dual-axis liquid-rate gyroscope prototype applying a single-axis liquid-rate microgyroscope and confirmed performance in experiments. Scale factors for theXandY-axes measured in the gyroscope are -24 mV/°/s and -21 mV/°/s. Experimental results confirmed the dual-axis liquid-rate gyroscope potential.

Establishment of All Digital Closed-Loop Interferometric Fiber-Optic Gyroscope and Scale Factor Comparison for Open-Loop and All Digital Closed-Loop Configurations

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper covers the design details of an all digital closed-loop interferometric fiber-optic gyroscope (ADCL-IFOG) prototype, constructed in TUBITAK UME, and scale factor comparison between open-loop and ADCL-IFOG prototypes with sine wave biasing modulation. The output of demodulation circuit, proportional to the applied rotation rate, was sampled by AD7714YN analog-to-digital converter (ADC), operated in 16 bit resolution. Error voltage, generated by microcomputer – controlled LTC 1667CG, 14 bit digital to analog converter (DAC), was sent to the phase modulator through a linear summing circuit to make Sagnac Phase Shift zero, depending on the rotation direction. For this implementation, the ultimate rotation rate of 1.84 (<formula formulatype="inline"><tex Notation="TeX">$^{\circ}/{\hbox{h}}$</tex> </formula>) was nullified. The averaged sensitivity of the proposed closed-loop IFOG in unit of error voltage applied to the phase modulator was determined as 132.65 <formula formulatype="inline"><tex Notation="TeX">$\mu \hbox{V}/(^{\circ}/{\hbox{h}}$</tex> </formula>). The scale factors of both the open-loop and ADCL-IFOG prototypes were compared in a range of 1–15270 (<formula formulatype="inline"> <tex Notation="TeX">$^{\circ}/\hbox{h}$</tex></formula>) rotation rate, corresponding to Sagnac Phase Shifts varying from 0.00115 (<formula formulatype="inline"> <tex Notation="TeX">$^{\circ}$</tex></formula>) to 17.57448 (<formula formulatype="inline"> <tex Notation="TeX">$^{\circ}$</tex></formula>). The maximum peak to peak noise and the bias stability of ADCL-IFOG prototype were determined as 4.97 (<formula formulatype="inline"><tex Notation="TeX">$^{\circ}/\hbox{h}$</tex> </formula>) and 1.48 (<formula formulatype="inline"><tex Notation="TeX">$^{\circ}/\hbox{h}$</tex> </formula>) at 23.0<formula formulatype="inline"><tex Notation="TeX">$~^{\circ}\hbox{C}$</tex> </formula>, respectively. </para>

Design details and characterization of all digital closed-loop interferometric fiber optic gyroscope with superluminescent light emitting diode

This paper describes the design details and the characterization of an all digital closed-loop (ADCL) interferometric fiber optic gyroscope (IFOG) Prototype with sine wave biasing modulation and SLED emiting at 1288.9 nm, constructed in TUBITAK UME. Electronic feedback section of ADCL-IFOG is composed of 16 bit AD7714YN ADC, 14 bit-LTC1667CG DAC, fully controlled and synchronized by 89C51 microcontroller. The averaged sensitivity of the ADCL-IFOG prototype in unit of error voltage applied to the phase modulator was calculated as 132.65 μV/(°/h) which equals to a scale factor of 7.53888 (°/h)/mV with a standard deviation of 0.85% for a range of 1–15270 (°/h) rotation rate, corresponding to a range of Sagnac phase shifts varying from 0.00115 to 17.57448 (°). The maximum peak to peak noise and the bias stability of the prototype were determined as 4.97 and 1.48 (°/h) at 23.0°C, respectively. The variation of the noise and bias stability on a temperature range of 23.0–42.0°C was observed.

Optical detection of the coriolis force on a silicon micromachined gyroscope

We report on the optical characterization of a micromachined gyroscope prototype for automotive applications, by means of feedback interferometry. In order to directly detect the rotation-induced Coriolis force, we have developed a compact and stable interferometric setup, which has been positioned inside a small vacuum bell, mounted on a rotating table. By this setup, which has a noise limit of the order of 10/sup -11/ m/(Hz) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> 2/, we have measured the gyro responsivity curve, demonstrating the feasibility of the optical interferometric detection of the in-plane response of a MEMS sensor. In addition, we have carried out the full mechanical characterization of the device at different pressures, and we have performed the matching of the gyro resonance frequencies by the interferometric monitoring. Our gyro had a resonance frequency of 3986 Hz for both axes after tuning; at a pressure of 7 10/sup -2/ torr, the quality factor were Q=18000 for the driving axis and Q=1800 for the sensing axis, while the measured responsivity was 7 10/sup -10/ m/(°/s). The optical characterization represents an important feedback to the designer and is especially powerful in the case of prototypes for which the on-board electronics is not yet available.

A novel bulk micromachined gyroscope with slots structure working at atmosphere

Abstract Design, fabrication and testing of a novel silicon micromachined gyroscope prototype with slots structure are presented. The device structure which we called “slots gyroscope” consists of a proof mass with slots linked up to substrate by suspend springs and is fabricated by silicon–glass bonding and deep reactive ion etching (DRIE). The gyroscope makes use of electrostatic driving and capacitive sensing. As the proof mass used as the movable electrodes is parallel to the plane of fixed driving and sensing electrodes, there is only slide film damping in the driving and sensing mode. The gyroscope can operate at atmospheric pressure due to almost same high quality factor in the sensing direction and driving direction. The experiment result shows that the drive and sense mode resonant frequencies are 460.4 and 549.6 Hz, respectively, and the quality factor of the drive and sense are 102.5 and 106.5, respectively at atmospheric pressure. The scale factor and non-linearity of the micromachined gyroscope are 20 mV/(° s) and 0.56%, respectively at atmospheric pressure.

Optical fiber gyroscope for automotive navigation

The use of an optical fiber gyroscope in automotive navigation is reported. The performance requirements for a navigational gyroscope are discussed in terms of the input range, resolution, and bias and scale errors. The OFG-3, an automotive optical fiber gyroscope prototype, is introduced, and its error sources are related to the gyroscope designs. The gyroscope is made of polarization maintaining fibers and incorporates optical phase modulation and synchronous demodulation techniques. The gyroscope electronics restrict the resolution and the bias error, while the optics dominate the scale error. The microcomputer in the electronics compensate for the scale error, and the OFG-3 meets navigational requirements. Automotive navigation has been demonstrated using the gyroscope in combination with a map-matching algorithm. >