Periodic Error Compensation for Quartz MEMS Gyroscope Drift of INS

In order to improve the navigation accuracy of an inertial navigation system （INS）, composed of quartz gyroscopes, the existing real-time compensation methods for periodic errors in quartz gyroscope drift and the periodic error term relationship between sampled original data and smoothed data are reviewed. On the base of the results, a new compensation method called using former period characteristics to compensate latter smoothness data （UFCL for short） method is proposed considering the INS working characteristics. This new method uses the original data without smoothing to work out an error conversion formula at the INS initial alignment time and then compensate the smoothed data errors by way of the formula at the navigation time. Both theoretical analysis and experimental results demonstrate that this method is able to cut down on computational time and raise the accuracy which makes it a better real-time compensation approach for periodic error terms of quartz micro electronic mechanical system （MEMS） gyroscope＇s zero drift.

A Practical Pll-Based Drive Circuit with Ultra-Low-Noise Tia for Mems Gyroscope

A novel phase-locked loop( PLL)-based closed-loop driving circuit with ultra-low-noise trans-impedance amplifier( TIA) is proposed. The TIA is optimized to achieve ultra-low input-referred current noise. To track drive-mode resonant frequency and reduce frequency jitter of actuation voltage,a PLL-based driving technique is adopted. Implemented on printed circuit board( PCB),the proposed driving loop has successfully excited MEMS element into resonance,with a settling time of 3 s. The stable frequency and amplitude of TIA output voltage are 10.14 KHz and 800 mVPP,respectively. With sense-channel electronics,the gyroscope exhibits a scale factor of 0.04 mV/°/s and a bias instability of 57.6°/h,which demonstrates the feasibility of the proposed driving circuit.

Novel On-Line North-Seeking Method Based on a Three-Axis MEMS Gyroscope

A novel on-line north-seeking method based on a three-axis micro-electro-mechanical system(MEMS)gyroscope is designed.This system processes data by using a Kalman filter to calibrate the installation error of the three-axis MEMS gyroscope in complex environment.The attitude angle updating for quaternion,based on which the attitude instrument will be rotated in real-time and the true north will be found.Our experimental platform constitutes the dual-axis electric rotary table and the attitude instrument,which is developed independently by our scientific research team.The experimental results show that the accuracy of north-seeking is higher than 1°,while the maximum root mean square error and the maximum mean absolute error are 0.906 7 and 0.910 0,respectively.The accuracy of north-seeking is much higher than the traditional method.

Adaptive tracking control of an MEMS gyroscope with H-infinity performance

Microelectromechanical systems (MEMSs) pose unique measurement and control problems compared with conventional ones because of their small size,low cost,and low power consumption.The vibrating gyroscope is one of those MEMS devices that have significant potential in many industry applications.When the MEMS gyroscope system is considered simultaneously with the coupling terms,the exogenous disturbances and the parameter variations,the controller design of this system becomes very challenging.This paper investigates the primary control problem of a perturbed vibrating MEMS gyroscope.A nonlinear robust adaptive control scheme is proposed for the drive axis of a vibrating MEMS gyroscope.By combining the dynamic surface control (DSC) method with the H-infinity disturbance attenuation technique,a simpler systematic design procedure is developed.The derived H-infinity controller has a simplified structure,and it can drive the drive axis to resonance,regulate the output amplitude of the drive axis to a desired value,and attenuate the generalized disturbances.The features of the derived controller are discussed and illustrated by the simulation of a closed-loop system.The analysis and simulation show that the obtained controller possesses good adaptability and robustness to system uncertainties.

A low-noise high-linearity interface ASIC for MEMS gyroscopes

This paper presents a continuous-time analog interface ASIC for use in MEMS gyroscopes. A charge sensitive amplifier with a chopper stabilization method is adopted to suppress the low-frequency noise. In order to cancel the effect caused by the gyroscope capacitive mismatch, a mismatch auto-compensation circuit is imple- mented. The gain and phase shift of the drive closed loop is controlled separately by an auto gain controller and an adjustable phase shifter. The chip is fabricated in a 0.35 μm CMOS process. The test of the chip is performed with a vibratory gyroscope, and the measurement shows that the noise floor is 0.003°/s√Hz, and the measured drift stability is 43°/h. Within -300 to 300°/s of rotation rate input range, the non-linearity is less than 0.1%.

Method for measuring the steering wheel angle of paddy field agricultural machinery by integrating RTK-GNSS and dual-MEMS gyroscope

Aiming at the application environment of paddy agricultural machinery with bumpy and undulating changes,the problems affecting the method for steering wheel angle measurement by MEMS gyroscope were analyzed,and a wheel angle measurement method combining Dual-MEMS gyroscope(dual MEMS gyroscope)and RTK-GNSS was designed.The adaptive weighting method was used to fuse the heading angle differentiation of RTK-GNSS,the MEMS gyroscope angle rate,and velocity data,and the rod-arm compensation was performed to accurately obtain the angle rates of the body and steering wheels of agricultural machinery;the difference between the combined angular rate of the steering wheel of the agricultural machinery and the angular rate of the agricultural machinery body was obtained,and the integrator is used to integrate the difference to get the wheel steering angle value,and the Kalman filter was designed to make feedback correction for the integration process of angle calculation to eliminate the errors caused by the gyroscope zero bias,random drift,and gyroscope rod arm effect,and to obtain the accurate value of wheel steering angle.A comparative test with the connecting rod wheel angle sensor was designed,and the results show that the maximum deviation is 4.99°,the average absolute average value is 1.61°,and the average standard deviation is 0.98°.The method in this study and the connecting rod wheel angle sensor were used on paddy farm machinery.The wheel angle measurement deviation of the proposed method and the connecting rod wheel angle sensor was not more than 1°,which is relatively small.It has good stability,speed adaptability,and dynamic responsiveness that meets the accuracy requirements of steering wheel angle measurement for paddy field agricultural machinery unmanned driving and can be used instead of connecting rod angle sensors for unmanned agricultural machinery.

An improved noise reduction transformation for algorithm based on wavelet MEMS gyroscope

To solve the large noise problem for the low- precision gyroscopes in micro-electro mechanical systems （MEMS） of inertial navigation system, an improved noise reduction method, based on the analyses of the fast Fourier transformation （FFT） noise reduction principle and the simple wavelet noise reduction principle, was proposed. Furthermore, the FFT noise reduction method, the simple wavelet noise reduction method and the improved noise reduction method were comparatively analyzed and experimentally verified in the case of the constant rate and dynamic rate. The experimental analysis results showed that the improved noise reduction method had a very good result in the noise reduction of the gyroscope data at different fi：equencies, and its performance was superior to those of the FFT noise reduction method and the simple wavelet noise reduction method.

Fabrication and characterization of an SOI MEMS gyroscope

This paper presents an SOI（silicon on insulator） MEMS（micro-electro-mechanical systems） vibratory gyroscope that was fabricated using bulk micromachining processes.In the gyroscope architecture,a frame structure that nests the proof mass is used to decouple the drive motion and sense motion.This approach ensures that the drive motion is well aligned with the designed drive axis,and minimizes the actual drive motion component along the sense detection axis.The thickness of the structural layer of the device is 100μm,which induces a high elastic stiffness in the thickness direction,so it can suppress the high-order out-of-plane resonant modes to reduce deviation.In addition,the dynamics of the gyroscope indicate that higher driving mass brings about higher sensing displacements.The thick structural layer can improve the output of the device by offering a sufficient mass weight and large sensing capacitance.The preliminary test results of the vacuum packaged device under atmospheric pressure will be provided.The scale factor is 1.316×10^-4 V/（deg/s）,the scale factor nonlinearity and asymmetry are 1.87%and 0.36%,the zero-rate offset is 7.74×10^4 V,and the zero-rate stability is 404 deg/h,respectively.

The effect of parasitic charge on the output stability of MEMS gyroscopes

Output voltage drifting was observed in MEMS gyroscopes. Other than the quadrature error, frequency mismatch and quality factor, the dielectric parasitic charge was thought to be a major determinant. We studied the mechanism and variation of the parasitic charge in the MEMS gyroscopes, and analyzed the effect of the parasitic charge on the output stability. This phenomenon was extremely obvious in the Pyrex encapsulated MEMS gyroscopes. Due to the DC voltage required for the electrostatic actuation, the parasitic charge in the dielectric layer would accumulate and induce a residual voltage. This voltage had an impact on the resonant frequency of the gyroscopes, so as to affect the output stability. The theoretical studies were also confirmed by our experimental results. It was shown that the parasitic charge was harmful to the output stability of MEMS gyroscopes.

Temperature compensation method for low cost three-axis MEMS digital angular rate gyroscopes

In recent years,a large number of small volume,low cost micro electro mechanical systems（MEMS）digital three-axis angular rate gyroscopes have been developed and widely used in civil and military fields.However,these kinds of gyroscopes have poor performances in initial zero-bias,temperature drift,In-Run bias stability,bias repeatability,etc.,their output errors need to be compensated before being used.Based on a lot of experiments,the temperature drift and the initial zero-bias are the major error sources in the MEMS gyroscopes output data.Due to the poor repeatability of temperature drift,the temperature compensation coefficients need to be recalculated every time before using.In order to recalculate parameters of the temperature compensation model quickly,a 1st-order polynomial model of temperature is established,then a forgetting factor recursive least squares estimator will be adopted to identify the model parameters in real time.Static and dynamic experimental data shows that this method removed/compensated the temperature drift and initial zero-bias from the output of the gyroscopes effectively.

Suppressing the mechanical quadrature error of a quartz double-H gyroscope through laser trimming

In this paper, we introduce a z-axis quartz gyroscope using a double-H tuning fork, which has a high sensitivity. However, it also causes a large mechanical quadrature error. The laser trimming method is used to suppress this error at quartz level. The trimming law is obtained through the finite element method （FEM）. A femtosecond laser processing system is used to trim the gold balancing masses on the beams, and experimental results are basically consistent with the simulated ones. The mechanical quadrature error is suppressed by 96%, from 26.3° s-1 to 1.1° s-1. Nonlinearity changes from 1.48% to 0.30%, angular random walk （ARW） is reduced from 2.19° h-1/2 to 1.42° h-1/2, and bias instability is improved by a factor of 7.7, from 197.6° h-1 to 25.4° h-1.

Nonlinear Performance of MEMS Vibratory Ring Gyroscope

Micro-electro-mechanical system(MEMS)gyroscopes are an important sort of inertial sensor for identifying parameters of spinning structures,such as the spinning speed and angular deviation,based on the Coriolis effect.In this paper,the nonlinear mechanism of MEMS vibratory ring gyroscopes is analyzed by applying a fully coupled nonlinear model,in which the gyroscopic coupling and geometrically and structurally nonlinear couplings are all taken into account.The coupled differential equations governing the drive and sense motions are established via the Lagrangian equations.Numerical simulation is conducted,and the key nonlinear components and energy transfer behaviors between the drive and sense modes are elucidated.It is revealed that the cubic rigidity nonlinearity is another significant factor leading to the coupling between the drive and sense modes other than the gyroscopic coupling.Perturbation analysis is also carried out by using the method of multiple scales.The nonlinear frequency-amplitude responses of the drive and sense vibrations are obtained,and comprehensive parametric studies are performed.The significant effects of system damping,excitation amplitude,drive amplitude and spinning speed on the responses are discussed,which will facilitate to improve the nonlinear performance and sensitivity of the gyroscope.

Substrate-decoupled,bulk-acoustic wave gyroscopes:Design and evaluation of next-generation environmentally robust devices

This paper reports on a new type of high-frequency mode-matched gyroscope with significantly reduced dependencies on environmental stimuli such as temperature,vibration,and shock.A novel stress-isolation system is used to effectively decouple an axis-symmetric bulk-acoustic wave(BAW)vibratory gyro from its substrate,minimizing the effect that external sources of error have on the offset and scale factor of the device.Substrate-decoupled(SD)BAW gyros with a resonance frequency of 4.3 MHz and Q values near 60000 were implemented using the high aspect ratio poly and single-crystal silicon(HARPSS)process to achieve ultra-narrow capacitive gaps.Wafer-level packaged sensors were interfaced with a customized application-specific integrated circuit(ASIC)to achieve low variations in the offset across temperature(±26°s^(−1) from−40 to 85℃),supreme random-vibration immunity(0.012°s^(−1) gRMS−1)and excellent shock rejection.With a scale factor of 800μV(°s^(−1))^(−1),the SD-BAW gyro system attains a large full-scale range(±1250°s^(−1))with a non-linearity of less than 0.07%.A measured angle-random walk(ARW)of 0.39°/√h and a bias instability of 10.5°h^(−1) are dominated by the thermal and flicker noise of the integrated circuit(IC),respectively.Additional measurements using external electronics show bias-instability values as low as 3.5°h−1,which are limited by feed-through signals coupled from the drive loop to the sense channel,which can be further reduced through proper re-routing of the gyroscope pin-out configuration.

Resonant pitch and roll silicon gyroscopes with sub-micron-gap slanted electrodes:Breaking the barrier toward high-performance monolithic inertial measurement units

This paper presents the design,fabrication,and characterization of a novel high quality factor(Q)resonant pitch/roll gyroscope implemented in a 40μm(100)silicon-on-insulator(SOI)substrate without using the deep reactive-ion etching(DRIE)process.The featured silicon gyroscope has a mode-matched operating frequency of 200 kHz and is the first out-of-plane pitch/roll gyroscope with electrostatic quadrature tuning capability to fully compensate for fabrication non-idealities and variation in SOI thickness.The quadrature tuning is enabled by slanted electrodes with sub-micron capacitive gaps along the(111)plane created by an anisotropic wet etching.The quadrature cancellation enables a 20-fold improvement in the scale factor for a typical fabricated device.Noise measurement of quadrature-cancelled mode-matched devices shows an angle random walk(ARW)of 0.63°√h^(−1) and a bias instability of 37.7°h^(−1),partially limited by the noise of the interface electronics.The elimination of silicon DRIE in the anisotropically wet-etched gyroscope improves the gyroscope robustness against the process variation and reduces the fabrication costs.The use of a slanted electrode for quadrature tuning demonstrates an effective path to reach high-performance in future pitch and roll gyroscope designs for the implementation of single-chip high-precision inertial measurement units(IMUs).

A Miniature Video Stabilization System for Flapping-Wing Aerial Vehicles

In this paper,a miniature video stabilization system is designed to deal with the image jitter and motion blur problem for°apping-wing aerial vehicles(FWAVs).First,a light and two-axis pan–tilt(about 13 g)is built for the FWAV to counteract most of the jitter e®ect.Then,an electronic image stabilization method combined with a Micro-Electro Mechanical Systems(MEMSs)gyroscope is proposed to further stabilize the images.Finally,°ight experiment results show that the designed video stabilization system e®ectively improves the quality of aerial videos.