Calibration Method of Accelerometer Based on Rotation Principle Using Double Turntable Centrifuge

For linear accelerometers, calibration with a precision centrifuge is a key technology, and the input acceleration imposed on the accelerometer should be accurately obtained in the calibration. However, there are often errors in the installation of sample that make the calibration inaccurate. To solve installation errors and obtain the input acceleration in the calibration of the accelerometer, a calibration method based on the rotation principle using a double turntable centrifuge is proposed in this work. The key operation is that the sub-turntable is rotated to make the input axis of the accelerometer perpendicular to the direction of the centripetal acceleration vector. Models of installation errors of angle and radius were built. Based on these models, the static radius and input acceleration can be obtained accurately, and the calibration of the scale factor, nonlinearity and asymmetry can be implemented. Using this method, measurements of the MEMS accelerometer with a range of ±30 g were carried out. The results show that the discrepancy of performance obtained from different installation positions was smaller than 100 ppm after calibrating the input acceleration. Moreover, the results using this method were consistent with those using the back-calculation method. These results demonstrate that the effectiveness of our proposed method was confirmed. This method can measure the static radius directly eliminating the installation errors of angle and radius, and it simplifies the accelerometer calibration procedure.

Analysis of Dynamic p-y Curve Characteristics According to Mode Shape of Structure Using Shaking Table Tests

In the seismic design of pile foundations, a p-y curve representing the nonlinear behavior of the ground considering the dynamic load of the earthquake is required. Recently, p-y curve analyses reflecting the soil-structure interaction have been conducted, but studies on multilayer structures have not been investigated extensively. In this study, the p-y curve characteristics were analyzed, considering the influence of the ground-structure interaction based on the mode shape of the structure (no structure, single-story structure, and three-story structure) through shake table tests. It was found that (1) the bending moment and pile displacement increased with input acceleration, and (2) the maximum soil resistance and pile displacement occurred at the natural frequencies of each structure were observed. In addition, the bending moment, soil resistance, and p-y curve slope were higher in the single-story structure than in the three-story structure. The findings indicate that the seismic design simulated for a single-story structure is conservative.

An efficient design of dual-axis MEMS accelerometer considering microfabrication process limitations and operating environment variations

PurposeThis paper aims to present an efficient design approach for the micro electromechanical systems (MEMS) accelerometers considering design parameters affecting the long-term reliability of these inertial sensors in comparison to traditional iterative microfabrication and experimental characterization approach. Design/methodology/approachA dual-axis capacitive MEMS accelerometer design is presented considering the microfabrication process constraints of the foundry process. The performance of the MEMS accelerometer is analyzed through finite element method– based simulations considering main design parameters affecting the long-term reliability. The effect of microfabrication process induced residual stress, operating pressure variations in the range of 10 mTorr to atmospheric pressure, thermal variations in the operating temperature range of −40°C to 100°C and impulsive input acceleration at different input frequency values is presented in detail. FindingsThe effect of residual stress is negligible on performance of the MEMS accelerometer due to efficient design of mechanical suspension beams. The effect of operating temperature and pressure variations is negligible on energy loss factor. The thermal strain at high temperature causes the sensing plates to deform out of plane. The input dynamic acceleration range is 34 g at room temperature, which decreases with operating temperature variations. At low frequency input acceleration, the input acts as a quasi-static load, whereas at high frequency, it acts as a dynamic load for the MEMS accelerometer. Originality/valueIn comparison with the traditional MEMS accelerometer design approaches, the proposed design approach focuses on the analysis of critical design parameters that affect the long-term reliability of MEMS accelerometer.

Design of MEMS Capacitive Accelerometer for Automotive Airbag Application

The objective of this paper is to bring out the responsiveness of the capacitive accelerometer with changes in the input acceleration. The performance analysis of the device is done using COMSOL MULTIPHYSICS .It is analysed that when the capacitance reaches a threshold value, amplifying the electric signal the air bag could be initiated.3D capacitive accelerometers which are less prone to noise and temperature variations. They reduce the severity of the accident by sensing the sudden increase in negative acceleration and deployment of the airbags. The dependency between the acceleration and the capacitance has been analysed. The sensitivity of the device with respect to forces in real time accident conditions is observed.

A Low-g MEMS Accelerometer with High Sensitivity, Low Nonlinearity and Large Dynamic Range Based on Mode-Localization of 3-DoF Weakly Coupled Resonators

This paper presents a new design of microelectromechanical systems (MEMS) based low-g accelerometer utilizing mode-localization effect in the three degree-of-freedom (3-DoF) weakly coupled MEMS resonators. Two sets of the 3-DoF mechanically coupled resonators are used on either side of the single proof mass and difference in the amplitude ratio of two resonator sets is considered as an output metric for the input acceleration measurement. The proof mass is electrostatically coupled to the perturbation resonators and for the sensitivity and input dynamic range tuning of MEMS accelerometer, electrostatic electrodes are used with each resonator in two sets of 3-DoF coupled resonators. The MEMS accelerometer is designed considering the foundry process constraints of silicon-on-insulator multi-user MEMS processes (SOIMUMPs). The performance of the MEMS accelerometer is analyzed through finite-element-method (FEM) based simulations. The sensitivity of the MEMS accelerometer in terms of amplitude ratio difference is obtained as 10.61/g for an input acceleration range of ±2 g with thermomechanical noise based resolution of 0.22 and nonlinearity less than 0.5%.

Stiffening Behavior of Supine Humans during En Route Care Transport

Previous studies of human response to whole-body vibration demonstrated nonlinear softening behaviors with increasing vibration magnitudes. Most of these studies were conducted at relatively low vibration magnitudes of less than 3 m/s2 root mean square (RMS), and not much knowledge is available to show if this softening behavior exists when humans are exposed to higher vibration magnitudes. In this work, 26 participants were transported in a supine position inside an army medical vehicle on a road that simulated field scenarios and were exposed to input acceleration magnitudes at 0.60, 0.98, 1.32, 3.25, 5.58, and 5.90 m/s2 RMS. Motion response data were collected at the head, torso, and pelvis of the participants using inertial sensors. Transmissibility and coherence graphs were used to investigate the type of nonlinearity induced under these transport conditions. Participant responses showed softening behavior when the vibration magnitude increased from 0.60 to 0.98 to 1.32 m/s2 RMS. However, this response behavior changed to stiffening when the vibration magnitude increased to 3.25, 5.58, and 5.90 m/s2 RMS. In the stiffening range, the transmissibility of the torso transformed from two dominant peaks to a single peak, which may indicate a tonic muscle behavior. The resulting stiffening behaviors may be considered in the design of transport systems subject to rough terrains.

Machine Learning Augmentation in Micro-Sensor Assemblies

The size and power limitations in small electronic systems such as wearable devices limit their potential. Significant energy is lost utilizing current computational schemes in processes such as analog-to-digital conversion and wireless communication for cloud computing. Edge computing, where information is processed near the data sources, was shown to significantly enhance the performance of computational systems and reduce their power consumption. In this work, we push computation directly into the sensory node by presenting the use of an array of electrostatic Microelectromechanical systems (MEMS) sensors to perform colocalized sensing-and-computing. The MEMS network is operated around the pull-in regime to access the instability jump and the hysteresis available in this regime. Within this regime, the MEMS network is capable of emulating the response of the continuous-time recurrent neural network (CTRNN) computational scheme. The network is shown to be successful at classifying a quasi-static input acceleration waveform into square or triangle signals in the absence of digital processors. Our results show that the MEMS may be a viable solution for edge computing implementation without the need for digital electronics or micro-processors. Moreover, our results can be used as a basis for the development of new types of specialized MEMS sensors (ex: gesture recognition sensors).

Effect of Peak Excitation Frequency on Seismic Fatigue Damage of Plant Pipelines

In a previous report, a new method of calculating the approximate seismic cumulative fatigue damage of plant pipelines was developed, in which the sum of the cumulative absolute velocities (CAV) of the pipeline response per cycle was calculated, and the result was applied to the allowable vibration velocity described in the ASME Operation and Maintenance (O/M) code 2012. The new method provided a conservative value of cumulative fatigue damage. In this present study, a parameter showing the effect of a concentrated mass attached to the tip of a cantilever pipe was obtained as a function of the ratio of the concentrated mass to the mass of the cantilever pipe by eigenmode calculation using ABAQUS. In the previous report, the new method was based on the relative response of the pipeline, whereas in this present study, the application of the method was expanded to evaluations using the CAV of the excitation input for each cycle. We conducted the fast forward simulation of a real earthquake to determine the effect of the peak frequency change on cumulative fatigue damage, and we found that the response of cumulative fatigue damage at the peak frequency tends to decrease with increasing peak excitation frequency, which was consistent with the results obtained using the previously reported new method. Both the new method and the newly expended method are based on the ASME O/M code, and the results obtained by these methods suggest that the peak frequency tends to affect general pipelines. In the calculations, when the configuration of the pipeline is fixed and the mode shape does not change, the cumulative fatigue damage was found to decrease with increasing peak frequency of input acceleration. If the mode shape changes with the peak input acceleration frequency, then cumulative fatigue damage is affected. Moreover, if the participation factor has a larger value in a higher mode, the cumulative fatigue damage also has a larger value.

Implementasi Sensor IMU untuk mengetahui Sudut Elevasi Kendaraan menggunakan Metode Least Square

ABSTRAKKemiringan jalan menyebabkan pengendara sepeda motor lebih berhati-hati dalam mengendarai kendaraannya. Selain untuk keamanan, sudut elevasi jalan dapat mempengaruhi dalam pengendalian kendaraan sehingga dapat lebih menghemat energi. Pada paper ini sensor Inertial Measurement Unit (IMU) digunakan untuk mengetahui kemiringan kendaraan sepeda motor (naik/turun dan condong kiri/kanan). Dalam perancangannya beberapa data akselerasi dari sensor accelerometer IMU diolah dengan regresi sehingga diperoleh persamaan regresi yang kemudian digunakan untuk memperbanyak data sehingga data tersebut dapat digunakan untuk prediksi model antara 3 input nilai akselerasi dan 2 output nilai kemiringan sudut kendaraan. Prediksi model berhasil dengan indentifikasi menggunakan metode Least Square. Dari data pengamatan diperoleh bahwa rata-rata kesalahan absolut untuk kemiringan naik/turun dan condong kiri/kanan antara 5 o s/d 7 o, namun belum berhasil untuk sudut yang besar (70 o s/d 90 o).Kata kunci: IMU, accelerometer, sudut elevasi, Arduino, Least Square ABSTRACTThe slope of the road leads to awareness of motorcyclists ini riding their motorcycle addition to safety, the elevation angle of the road can affect vehicle control so that it can save more energy. In this paper the IMU sensor is used to determine the slope of a motorcycle (up / down and leaning left / right). In the design of some acceleration data from the IMU accelerometer sensor is processed so that the regression equation is obtained. The regression equation is used to generate the data to predict the model 3 input acceleration value and 2 output slope value of the vehicle. Model prediction was successful by identification using the Least Square method. Obtained from observational data that the average absolute error for the slope up / down and leaning left / right between 5 o to 7 o, but has not been successful for wide angles (70 o to 90 o).Keywords: IMU, accelerometer, elevation angle, Arduino, Least Square

Reply to comment by Vallée et al. on “Earthquake-induced prompt gravity signals identified in dense array data in Japan”

Density perturbations accompanying seismic waves are expected to generate prompt gravity perturbations preceding the arrival of P-waves. Vallée et al. (Science 358:1164–1168, 2017, https://doi.org/10.1126/science.aao0746) reported the detection of such pre-P-wave signals in broadband seismograms during the 2011 Tohoku-oki earthquake. Kimura et al. (Earth Planets Space 71:27, 2019, https://doi.org/10.1186/s40623-019-1006-x) considered that their detection involved some uncertain points, including a concern regarding their signal processing procedure. Specifically, to remove the instrumental response, Vallée et al. (2017) applied acausal deconvolution to the seismograms truncated at the P-wave arrivals. Generally, acausal deconvolution produces artifacts at the edge of the time window. However, they did not present quantitative assessment whether the detected signals were artifacts due to the signal processing. To avoid this concern, Kimura et al. (2019) employed another procedure that eliminated acausal processes, resulting in the detection of a pre-P-wave signal with a statistical significance of 7σ in stacked broadband seismograms. Subsequently, Vallée et al. (Earth Planets Space 71:51, 2019, https://doi.org/10.1186/s40623-019-1030-x) commented that the procedure employed by Kimura et al. (2019) for the signal detection was inappropriate because it dismissed the low-frequency components of data. Although we admit the loss of low-frequency components in the data in Kimura et al. (2019), Vallée et al. (2019) have not yet provided a full account of the validity of their own procedure. Here, we assessed the validity of the procedure employed by Vallée et al. (2017) by quantitatively evaluating the magnitude of the acausal artifacts. First, we investigated how the input acceleration waveform, having an ideal signal-like shape, was distorted by their procedure. Their acausal deconvolution indeed generated a large-amplitude terminal artifact; however, it was removed by the causal band-pass filtering performed after the deconvolution and consequently became negligible. Next, we constrained the maximum amplitude of the artifact due to the noise in a seismogram and showed that it was sufficiently small compared to the reported signal amplitudes. These results suggest that the signal waveforms seen after their procedure were not artifacts but were representing the input acceleration with sufficient accuracy. Namely, their procedure well functions as a detection method for pre-P-wave signals. In the context of this validation, we replied to the comments of Vallée et al. (2019).