Research

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15 pages, 8042 KiB

Open AccessArticle

Analysis of the Frequency-Dependent Vibration Rectification Error in Area-Variation-Based Capacitive MEMS Accelerometers

by Shaolin Zhang, Zhi Li, Qiu Wang, Yuanxia Yang, Yongzhen Wang, Wen He, Jinquan Liu, Liangcheng Tu and Huafeng Liu

Micromachines 2024, 15(1), 65; https://doi.org/10.3390/mi15010065 - 28 Dec 2023

Viewed by 1037

Abstract

The presence of strong ambient vibrations could have a negative impact on applications such as high precision inertial navigation and tilt measurement due to the vibration rectification error (VRE) of the accelerometer. In this paper, we investigate the origins of the VRE using [...] Read more.

The presence of strong ambient vibrations could have a negative impact on applications such as high precision inertial navigation and tilt measurement due to the vibration rectification error (VRE) of the accelerometer. In this paper, we investigate the origins of the VRE using a self-developed MEMS accelerometer equipped with an area-variation-based capacitive displacement transducer. Our findings indicate that the second-order nonlinearity coefficient is dependent on the frequency but the VRE remains constant when the displacement amplitude of the excitation is maintained at a constant level. This frequency dependence of nonlinearity is a result of several factors coupling with each other during signal conversion from acceleration to electrical output signal. These factors include the amplification of the proof mass’s amplitude as the excitation frequency approaches resonance, the nonlinearity in capacitance-displacement conversion at larger displacements caused by the fringing effect, and the offset of the mechanical suspension’s equilibrium point from the null position of the differential capacitance electrodes. Through displacement transducer and damping optimization, the second-order nonlinearity coefficient is greatly reduced from mg/g

^{2}

to

μ

g/g

^{2}

. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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15 pages, 5376 KiB

Open AccessArticle

Silicon-Based Zipper Photonic Crystal Cavity Optomechanical System for Accelerometers

by Hongyu Tan, Debin Pan, Chensheng Wang and Yuan Yao

Micromachines 2023, 14(10), 1870; https://doi.org/10.3390/mi14101870 - 29 Sep 2023

Viewed by 773

Abstract

The cavity optomechanical accelerometer based on photonic crystal microcavities combines mechanical resonators with high-quality factor photonic crystal cavities. The mechanical vibrator is sensitive to weak force/displacement in mechanical resonance modes, which can achieve extremely low noise levels and theoretically reach the standard qillatum [...] Read more.

The cavity optomechanical accelerometer based on photonic crystal microcavities combines mechanical resonators with high-quality factor photonic crystal cavities. The mechanical vibrator is sensitive to weak force/displacement in mechanical resonance modes, which can achieve extremely low noise levels and theoretically reach the standard qillatum noise limit. It is an important development direction for high-precision accelerometers. This article analyzes the principle and structural characteristics of a zipper type photonic crystal cavity optomechanical accelerometer, and designs a silicon-based zipper type photonic crystal cavity and mechanical vibrator structure applied to the accelerometer. The influence of the structural parameters of the zipper cavity on the optical Q factor was analyzed in detail. The resonant frequency of the optical cavity was controlled around 195 THz by adjusting the structural parameters, and the mechanical resonance characteristics of the mechanical vibrator and the optical cavity were analyzed. The effective mass of the optical cavity was 30 pg, and, with the addition of the mechanical vibrator, the effective mass was 3.1 ng. The optical mechanical coupling rate reached the GHz/nm level, providing guidance for the manufacturing and characterization of silicon-based zipper cavity accelerometers. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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8 pages, 2920 KiB

Open AccessCommunication

Design and Demonstration of an In-Plane Micro-Optical-Electro-Mechanical-System Accelerometer Based on Talbot Effect of Dual-Layer Gratings

by Wenqing Chen, Li Jin, Zhibin Wang, Haifeng Peng and Mengwei Li

Micromachines 2023, 14(7), 1301; https://doi.org/10.3390/mi14071301 - 25 Jun 2023

Cited by 1 | Viewed by 928

Abstract

An ultrasensitive single-axis in-plane micro-optical-electro-mechanical-system (MOEMS) accelerometer based on the Talbot effect of dual-layer gratings is proposed. Based on the Talbot effect of gratings, the acceleration can be converted into the variation of diffraction intensity, thus changing the voltage signal of photodetectors. We [...] Read more.

An ultrasensitive single-axis in-plane micro-optical-electro-mechanical-system (MOEMS) accelerometer based on the Talbot effect of dual-layer gratings is proposed. Based on the Talbot effect of gratings, the acceleration can be converted into the variation of diffraction intensity, thus changing the voltage signal of photodetectors. We investigated and optimized the design of the mechanical structure; the resonant frequency of the accelerometer is 1878.9 Hz and the mechanical sensitivity is 0.14 μm/g. And the optical grating parameters have also optimized with a period of 4 μm and a grating interval of 10 μm. The experimental results demonstrated that the in-plane MOEMS accelerometer with an optimal design achieved an acceleration sensitivity of 0.74 V/g (with better than 0.4% nonlinearity), a bias stability of 75 μg and an acceleration resolution of 2.0 mg, suggesting its potential applications in smartphones, automotive electronics, and structural health detection. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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31 pages, 13975 KiB

Open AccessArticle

An Indoor Visual Positioning Method with 3D Coordinates Using Built-In Smartphone Sensors Based on Epipolar Geometry

by Ping Zheng, Danyang Qin, Jianan Bai and Lin Ma

Micromachines 2023, 14(6), 1097; https://doi.org/10.3390/mi14061097 - 23 May 2023

Viewed by 1132

Abstract

In the process of determining positioning point by constructing geometric relations on the basis of the positions and poses obtained from multiple pairs of epipolar geometry, the direction vectors will not converge due to the existence of mixed errors. The existing methods to [...] Read more.

In the process of determining positioning point by constructing geometric relations on the basis of the positions and poses obtained from multiple pairs of epipolar geometry, the direction vectors will not converge due to the existence of mixed errors. The existing methods to calculate the coordinates of undetermined points directly map the three-dimensional direction vector to the two-dimensional plane and take the intersection points that may be at infinity as the positioning result. To end this, an indoor visual positioning method with three-dimensional coordinates using built-in smartphone sensors based on epipolar geometry is proposed, which transforms the positioning problem into solving the distance from one point to multiple lines in space. It combines the location information obtained by the accelerometer and magnetometer with visual computing to obtain more accurate coordinates. Experimental results show that this positioning method is not limited to a single feature extraction method when the source range of image retrieval results is poor. It can also achieve relatively stable localization results in different poses. Furthermore, 90% of the positioning errors are lower than 0.58 m, and the average positioning error is less than 0.3 m, meeting the accuracy requirements for user localization in practical applications at a low cost. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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18 pages, 8219 KiB

Open AccessArticle

Performance Testing of Micro-Electromechanical Acceleration Sensors for Pavement Vibration Monitoring

by Zhoujing Ye, Ya Wei, Biyu Yang and Linbing Wang

Micromachines 2023, 14(1), 153; https://doi.org/10.3390/mi14010153 - 07 Jan 2023

Cited by 2 | Viewed by 1679

Abstract

Pavement vibration monitoring under vehicle loads can be used to acquire traffic information and assess the health of pavement structures, which contributes to smart road construction. However, the effectiveness of monitoring is closely related to sensor performance. In order to select the suitable [...] Read more.

Pavement vibration monitoring under vehicle loads can be used to acquire traffic information and assess the health of pavement structures, which contributes to smart road construction. However, the effectiveness of monitoring is closely related to sensor performance. In order to select the suitable acceleration sensor for pavement vibration monitoring, a printed circuit board (PCB) with three MEMS (micro-electromechanical) accelerometer chips (VS1002, MS9001, and ADXL355) is developed in this paper, and the circuit design and software development of the PCB are completed. The experimental design and comparative testing of the sensing performance of the three MEMS accelerometer chips, in terms of sensitivity, linearity, noise, resolution, frequency response, and temperature drift, were conducted. The results show that the dynamic and static calibration methods of the sensitivity test had similar results. The influence of gravitational acceleration should be considered when selecting the range of the accelerometer to avoid the phenomenon of over-range. The VS1002 has the highest sensitivity and resolution under 3.3 V standard voltage supply, as well as the best overall performance. The ADXL355 is virtually temperature-independent in the temperature range from −20 °C to 60 °C, while the voltage reference values output by the VS1002 and MS9001 vary linearly with temperature. This research contributes to the development of acceleration sensors with high precision and long life for pavement vibration monitoring. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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13 pages, 8653 KiB

Open AccessFeature PaperArticle

Ring-Core Fluxgate Sensor for High Operation Temperatures up to 220 °C

by Kaixin Yuan, Aimin Du, Lin Zhao, Shuquan Sun, Xiao Feng, Chenhao Zhang, Yiming Zhang and Huafeng Qin

Micromachines 2022, 13(12), 2158; https://doi.org/10.3390/mi13122158 - 07 Dec 2022

Cited by 2 | Viewed by 1257

Abstract

Fluxgate sensors are key devices for magnetic field surveys in geophysics. In areas such as deep drilling, fluxgate sensors may have to operate steadily at high temperatures for a prolonged period of time. We present an accordant ring-core type fluxgate sensor that is [...] Read more.

Fluxgate sensors are key devices for magnetic field surveys in geophysics. In areas such as deep drilling, fluxgate sensors may have to operate steadily at high temperatures for a prolonged period of time. We present an accordant ring-core type fluxgate sensor that is stable up to

220

°C. The high temperature consistency is achieved by using an Fe-based nanocrystalline magnetic core, PEEK structural components, an epoxy resin wrapping, as well as a broadband short-circuited working mode. The sensor was characterized at various temperatures up to

220

°C by evaluating impedance, hysteresis, permeability and sensitivity. We found a sensitivity of approximately 24 kV/T at

25

°C with an acceptable temperature coefficient of 742 ppm/°C throughout the range. The variation law of magnetic characteristics and their influence mechanism on output amplitude and phase are discussed. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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10 pages, 2816 KiB

Open AccessArticle

Study on the CHZ-II Gravimeter and Its Calibrations along Forward and Reverse Overlapping Survey Lines

by Haibo Tu, Kun Liu, Heng Sun, Qian Cui, Yuan Yuan, Sunjun Liu, Jiangang He and Lintao Liu

Micromachines 2022, 13(12), 2124; https://doi.org/10.3390/mi13122124 - 30 Nov 2022

Viewed by 1412

Abstract

The moving-base gravimeter is one of the key instruments used for Earth gravity survey. The accuracy of the survey data is closely related to the calibration precision of several key parameters, such as the damping delay time, the drift coefficient, the gravity scale [...] Read more.

The moving-base gravimeter is one of the key instruments used for Earth gravity survey. The accuracy of the survey data is closely related to the calibration precision of several key parameters, such as the damping delay time, the drift coefficient, the gravity scale factor, and the measurement accuracy. This paper will introduce the development of the CHZ-II gravimeter system in which a cylindrical sampling mass suspended vertically by a zero-length spring acts as a sensitive probe to measure specific force. Meanwhile, a GNSS (Global Navigation Satellite System) positioning system is employed to monitor the carrier motion and to remove the inertia acceleration. In order to achieve high-precision calibrations for the key parameters, a new calibration method performed along forward and reverse overlapping lines is proposed, which is used to calibrate the above parameters and to estimate the measurement accuracy of the instrument used for a normal gravity survey. The calibration principle and the shipboard calibration data processing method are introduced. The calibration was performed for three moving-base gravimeters and the corresponding results are determined, indicating that the method can significantly improve the accuracy of the parameters. For the CHZ-II gravimeter, the measurement accuracy of the survey is 0.471 mGal (1 mGal = 10⁻⁵ m/s²), which improved by 19.5% after applying the calibrated parameters. This method is also practical for use with aviation, marine and even vehicle-carried moving-base gravimeters. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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26 pages, 3847 KiB

Open AccessArticle

Research on Sparse Denoising of Strong Earthquakes Early Warning Based on MEMS Accelerometers

by Jiening Xia, Zhigao Chen, Jiang Yang, Yuxiu Chen, Benyan Tan and Zongxuan Wu

Micromachines 2022, 13(12), 2113; https://doi.org/10.3390/mi13122113 - 29 Nov 2022

Cited by 1 | Viewed by 1042

Abstract

In view of the fact that the noise in the same frequency band as the useful signal in the MEMS acceleration sensor observation data cannot be effectively removed by traditional filtering methods, a denoising method for strong earthquake signals based on the theory [...] Read more.

In view of the fact that the noise in the same frequency band as the useful signal in the MEMS acceleration sensor observation data cannot be effectively removed by traditional filtering methods, a denoising method for strong earthquake signals based on the theory of sparse representation and compressive sensing is proposed in this paper. This skillfully realized the separation of strong earthquake signals from noise by adopting a fixed dictionary and utilizing sparse characteristics. Furthermore, considering the weakness of the sparse denoising method based on the fixed dictionary in the high signal-to-noise ratio, a spare denoising method based on learning an over-complete dictionary is proposed. Through the initial given seismic data, the ideal over-complete dictionary is trained to achieve seismic data denoising. In addition, for the interference waves of non-seismic events, this paper proposes an idea based on sparse representation classification to remove such non-seismic interference directly. Combining the ideas of noise reduction and non-seismic event elimination, we can obtain a standard sparse anti-interference denoising model for earthquake early warning. It’s innovative that this model implements the sparse theory into the field of earthquake early warning. According to the experimental results, in the case of heavy noise, the denoising model based on sparse representation can reach average SNR of 8.73 and an average MSE of 29.53, and the denoising model based on compression perception can reach average SNR of 7.29 and an average MSE 41.34, and the denoising model based on learning dictionary can reach average SNR 11.07 and average MSE 17.32. The performance of these models is better than the traditional FIR filtering method (average SNR −0.73 and average MSE 260.37) or IIR filtering method (average SNR 4.73 and average MSE 73.95). On the other hand, the anti-interference method of the sparse classification proposed in this paper can accurately distinguish non-seismic interference events from natural earthquakes. The classification accuracy of the method based on the noise category of the selected test data set reaches 100% and achieves good results. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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12 pages, 3013 KiB

Open AccessArticle

A Robust Tracking Method for Multiple Moving Targets Based on Equivalent Magnetic Force

by Ying Wang, Qiang Fu and Yangyi Sui

Micromachines 2022, 13(11), 2018; https://doi.org/10.3390/mi13112018 - 18 Nov 2022

Cited by 5 | Viewed by 1202

Abstract

A ferromagnetic vehicle, such as a submarine, magnetized by the Earth’s magnetic field produces a magnetic anomaly field, and the tracking of moving targets can be realized through real-time analysis of magnetic data. At present, there are few tracking methods based on magnetic [...] Read more.

A ferromagnetic vehicle, such as a submarine, magnetized by the Earth’s magnetic field produces a magnetic anomaly field, and the tracking of moving targets can be realized through real-time analysis of magnetic data. At present, there are few tracking methods based on magnetic field vectors and their gradient tensor. In this paper, the magnetic field vector and its gradient tensor are used to calculate equivalent magnetic force. It shows the direction of the vector between the detector and the tracking targets for controlling the direction of motion of the detector and achieving the purpose of tracking. Compared with existing positioning methods, the proposed method is relatively less affected by instrument resolution and noise and maintains robustness when the velocity vectors of multiple magnetic targets change randomly. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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Review

Jump to: Research

17 pages, 8262 KiB

Open AccessReview

Recent Developments in Fabrication Methods and Measurement Schemes for Optically Pumped Magnetic Gradiometers: A Comprehensive Review

by Haifeng Dong, Hangfei Ye, Min Hu and Zongmin Ma

Micromachines 2024, 15(1), 59; https://doi.org/10.3390/mi15010059 - 27 Dec 2023

Viewed by 785

Abstract

Optically pumped gradiometers have long been utilized in measurement in the International Geomagnetic Reference Field (IGRF). With advancements in technologies such as laser diodes and microfabrication, integrated gradiometers with compact sizes have become available, enabling improvements in magnetoencephalography and fetal magnetocardiography within shielded [...] Read more.

Optically pumped gradiometers have long been utilized in measurement in the International Geomagnetic Reference Field (IGRF). With advancements in technologies such as laser diodes and microfabrication, integrated gradiometers with compact sizes have become available, enabling improvements in magnetoencephalography and fetal magnetocardiography within shielded spaces. Moreover, there is a growing interest in the potential of achieving biomagnetic source detection without shielding. This review focuses on recent developments in optically pumped magnetic field gradiometers, including various fabrication methods and measurement schemes. The strengths and weaknesses of different types of optically pumped gradiometers are also analyzed. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications)

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