MEMS Accelerometers Elfadel, Ibrahim (Abe) M; Ngo, Ha Duong; Rasras, Mahmoud
01/2019
eBook
Odprti dostop
Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development ...driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc.
This Special Issue on "MEMS Accelerometers" seeks to highlight research papers, short communications, and review articles that focus on:
Novel designs, fabrication platforms, characterization, optimization, and modeling of MEMS accelerometers.
Alternative transduction techniques with special emphasis on opto-mechanical sensing.
Novel applications employing MEMS accelerometers for consumer electronics, industries, medicine, entertainment, navigation, etc.
Multi-physics design tools and methodologies, including MEMS-electronics co-design.
Novel accelerometer technologies and 9DoF IMU integration.
Multi-accelerometer platforms and their data fusion.
Introduction
Physical activity (PA) is prospectively inversely associated with dementia risk, but few studies examined accelerometer measures of PA and sitting with rigorously‐adjudicated mild ...cognitive impairment (MCI) and dementia risk.
Methods
We examined the associations of accelerometer measures (PA and sitting) with incident MCI/probable dementia in the Women's Health Initiative (n = 1277; mean age = 82 ± 6 years)
Results
Over a median follow‐up of 4.2 years, 267 MCI/probable dementia cases were identified. Adjusted Cox regression HRs (95% CI) across moderate‐to‐vigorous PA (MVPA) min/d quartiles were 1.00 (reference), 1.28 (0.90 to 1.81), 0.79 (0.53 to 1.17), and 0.69 (0.45 to 1.06); P‐trend = 0.01. Adjusted HRs (95% CI) across steps/d quartiles were 1.00 (reference), 0.73 (0.51 to 1.03), 0.64 (0.43 to 0.94), and 0.38 (0.23 to 0.61); P‐trend < 0.001. The HR (95% CI) for each 1‐SD increment in MVPA (31 min/d) and steps/d (1865) were 0.79 (0.67 to 0.94) and 0.67 (0.54 to 0.82), respectively. Sitting was not associated with MCI/probable dementia.
Discussion
Findings suggest ≥ moderate intensity PA, particularly stepping, associates with lower MCI and dementia risk.
Highlights
Few studies have examined accelerometer‐measured physical activity, including steps, and sitting with incident ADRD.
Moderate‐to‐vigorous physical activity and steps, but not light physical activity or sitting, were inversely associated with lower ADRD risk.
Among older women, at least moderate intensity physical activity may be needed to reduce ADRD risk.
There are many physiological parameters recorded by devices that are becoming more affordable, precise and accurate. However, the lack of development in the recording of voice parameters from the ...physiological or medical point of view is striking, given that it is a fundamental tool for the work of many people and given the high incidence and prevalence of voice pathologies that affect people's communication. In this paper we perform a complete literature review on the dosimeters used in voice research and to present a prototype dosimeter with a pilot study to show its capabilities.
We conducted a literature review using the keywords MONITORING, PHONATION, ACCUMULATOR, PORTABLE, DOSIMETRY, VOICE searching in PubMed, Trip Database, HONcode, and SciELO search engines. From our review of dosimeter designs, we created our own prototype consisting of two main components: a Knowles Electronics BU-7135-0000 accelerometer mounted on a neck brace; and the ultra-low power MSP430FR5994 microcontroller. The selected sampling frequency was 2048 Hz. The device calculates the F0 every 250 ms and the amplitude and phonation activity every 31.25 ms. A pilot study was conducted using 2 subjects: one male during 11 days and one female during 14 days.
This work includes devices that have been created during the last 45 years as tools for the diagnosis and monitoring of the treatment of cases of vocal pathology and for the detection of phonatory patterns or risk situations for developing voice disorders or vocal pathologies. We also present recordings with our new device on the pattern of daily talk time, the fundamental frequency and the relative intensity of two subjects on different days.
Interesting work has been done in the development of voice dosimeters with different approaches. In our experience it is not possible to access them for research and they are not yet in clinical use. It is possible that a joint approach with voice and voice disorders professionals and engineers working closely together could take advantage of current technology to develop a fully portable, useful, and efficient system.
Rotating Accelerometer Gravity Gradientmeter (RAGG) is the only gravity gradient measuring device in the world to achieve commercial applications. When the parameter consistency among multiple ...accelerometers of the RAGG is not sufficient, its combined output cannot effectively suppress common-mode noise in the environment. A method for suppressing RAGG's linear and angular motion noise is presented in this paper by projecting the parameters, including scale factor, misalignment angle, second-order terms and cross-coupling terms, onto the cartesian coordinate system of the turntable plane. Proposing the algorithm implementation scheme of three effective scale factor solver loops, and for further canceling the motion residual error, high precision gyroscope compensation loops is introduced. The added error compensation loop obtains the angular acceleration by differencing the angular velocity measured by the gyroscope, which in turn adjusts the loop parameters. Experimental results show that with the proposed method, the noise suppression of linear motion common-mode acceleration reaches 6.5 orders of magnitude, that is, the noise level 2.7 × 10 -8 g/ √ Hz of the accelerometer at the rotation frequency, and the angular motion common-mode acceleration noise is suppressed by 6 orders of magnitude, and the noise level 6.8×10 -8 g/ √ Hz of the accelerometer at the swing frequency is also obtained.
INTRODUCTION/PURPOSEThe goal of this program was to determine the feasibility of a novel noninvasive, highly miniaturized optomechanical earbud sensor for accurately estimating total energy ...expenditure (TEE) and maximum oxygen consumption (V˙O2max). The optomechanical sensor module, small enough to fit inside commercial audio earbuds, was previously developed to provide a seamless way to measure blood flow information during daily life activities. The sensor module was configured to continuously measure physiological information via photoplethysmography and physical activity information via accelerometry. This information was digitized and sent to a microprocessor where digital signal-processing algorithms extract physiological metrics in real time. These metrics were streamed wirelessly from the earbud to a computer.
METHODSIn this study, 23 subjects of multiple physical habitus were divided into a training group of 14 subjects and a validation group of 9 subjects. Each subject underwent the same exercise measurement protocol consisting of treadmill-based cardiopulmonary exercise testing to reach V˙O2max. Benchmark sensors included a 12-lead ECG sensor for measuring HR, a calibrated treadmill for measuring distance and speed, and a gas-exchange analysis instrument for measuring TEE and V˙O2max. The earbud sensor was the device under test. Benchmark and device under test data collected from the 14-person training data set study were integrated into a preconceived statistical model for correlating benchmark data with earbud sensor data. Coefficients were optimized, and the optimized model was validated in the 9-person validation data set.
RESULTSIt was observed that the earbud sensor estimated TEE and V˙O2max with mean ± SD percent estimation errors of −0.7 ± 7.4% and −3.2 ± 7.3%, respectively.
CONCLUSIONThe earbud sensor can accurately estimate TEE and V˙O2max during cardiopulmonary exercise testing.
MEMS accelerometers have benefits of low cost and small volume, however their long-term stability is limited by the fabrication mismatches. This paper proposes a self-test and calibration technique ...for differential MEMS accelerometers, to reduce the effect of flicker noise in reference voltages due to nonlinear stiffness mismatch in two channels. Through detecting the frequency response induced by the sinusoidal test signal, the oscillating amplitude of the two channels is properly adjusted to meet a theoretically derived noise cancellation condition. A numerical model is established based on practical mechanical parameters of the MEMS structures to simulate the proposed system, and optimize the key design parameters. Finally, a prototype including a MEMS accelerometer chip and an FPGA-based control circuit is implemented to verify the suggested approaches. Compared to that without the proposed technique, the 1-h bias-instability of the SOA is reduced from 6.31 μg to 3.44 μg. At different reference voltages from 1.09 V to 1.33 V, the decrease in instability is between 21.7 % and 45.5 %.
Purpose The ability to actively adjust walking speed is fundamental and the factors enabling it should be assessed. The present study aimed to demonstrate how active gait speed is kinematically ...adjusted. Participants and Methods Walking acceleration and deceleration were evaluated in 16 healthy adults using three-axis accelerometers and surface electromyographs. The root mean square (RMS) of each axis in the center-of-gravity acceleration was calculated as an index of gait stability. Electron myograph data were obtained from images captured of the right lower muscles, and the integral value of total muscle activity per gait cycle was calculated. Results The RMS of each axis increased during acceleration and decreased during deceleration. The integral values of total activity of the gastrocnemius, biceps femoris, and tibialis anterior muscles increased in acceleration. In contrast, the values increased in the biceps femoris but decreased in other muscles during deceleration. Conclusion These results suggest that the specific kinematic mechanisms of each factor regulate the acceleration and deceleration of walking. In addition, these mechanisms and factors indicate how exercise therapy may be used in rehabilitation to improve the ability to adjust walking speed in daily life.
To understand how device-measured sedentary behaviour and physical activity are related to all-cause mortality in older men, an age group with high levels of inactivity and sedentary behaviour.
...Prospective population-based cohort study of men recruited from 24 UK General Practices in 1978-1980. In 2010-2012, 3137 surviving men were invited to a follow-up, 1655 (aged 71-92 years) agreed. Nurses measured height and weight, men completed health and demographic questionnaires and wore an ActiGraph GT3x accelerometer. All-cause mortality was collected through National Health Service central registers up to 1 June 2016.
After median 5.0 years' follow-up, 194 deaths occurred in 1181 men without pre-existing cardiovascular disease. For each additional 30 min in sedentary behaviour, or light physical activity (LIPA), or 10 min in moderate to vigorous physical activity (MVPA), HRs for mortality were 1.17 (95% CI 1.10 to 1.25), 0.83 (95% CI 0.77 to 0.90) and 0.90 (95% CI 0.84 to 0.96), respectively. Adjustments for confounders did not meaningfully change estimates. Only LIPA remained significant on mutual adjustment for all intensities. The HR for accumulating 150 min MVPA/week in sporadic minutes (achieved by 66% of men) was 0.59 (95% CI 0.43 to 0.81) and 0.58 (95% CI 0.33 to 1.00) for accumulating 150 min MVPA/week in bouts lasting ≥10 min (achieved by 16% of men). Sedentary breaks were not associated with mortality.
In older men, all activities (of light intensity upwards) were beneficial and accumulation of activity in bouts ≥10 min did not appear important beyond total volume of activity. Findings can inform physical activity guidelines for older adults.
Summary
Moderate‐to‐vigorous‐intensity physical activity (MVPA) is important for childhood obesity prevention and treatment, yet declines with age. Timing and magnitude of the decline in MVPA in ...children and adolescents are unclear but important for informing effective obesity intervention development. This systematic review aimed to determine and compare the year‐to‐year changes in MVPA among children and adolescents. Longitudinal studies were identified by searching 10 relevant databases up to December 2018. Studies were eligible for inclusion if they reported accelerometer‐assessed MVPA (min day−1) separately for boys and girls and had follow‐up duration of at least 1 year. After screening 9,232 studies, 52 were included representing 22,091 aged 3 to 18 year olds (boys=8,857; girls=13,234). Pooled‐analysis of the relative change in MVPA per year showed a decline of −3.4% (95% CI, −5.9 to −0.9) in boys and −5.3% (95% CI, −7.6 to −3.1) in girls, across all age groups. There were notable declines in MVPA at age 9 for both boys (−7.8%, 95% CI, −11.2 to −4.4) and girls (−10.2%, 95% CI, −14.2 to −6.3). The relative decline in MVPA affects both sexes from an early age; however, it is greater among girls. Interventions to promote MVPA should start before adolescence.
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