Accelerometer Output Research Articles

Calibrating acoustic acceleration transmitters for estimating energy use by wild adult Pacific salmon

This study is the first to calibrate acceleration transmitters with energy expenditure using a vertebrate model species. We quantified the relationship between acoustic accelerometer output and oxygen consumption across a range of swim speeds and water temperatures for Harrison River adult sockeye salmon (Oncorhynchus nerka). First, we verified that acceleration transmitters with a sampling frequency of 10Hz could be used as a proxy for movement in sockeye salmon. Using a mixed effects model, we determined that tailbeat frequency and acceleration were positively correlated (p<0.0001), independent of tag ID. Acceleration (p<0.0001) was positively related to swim speed while fork length (p=0.051) was negatively related to swim speed. Oxygen consumption and accelerometer output (p<0.0001) had a positive linear relationship and were temperature dependent (p<0.0001). There were no differences in swim performance (F2,12=1.023, p=0.820) or oxygen consumption (F1,12=0.054, p=0.332) between tagged and untagged individuals. Five tagged fish were released into the Fraser River estuary and manually tracked. Of the five fish, three were successfully tracked for 1h. The above relationships were used to determine that the average swim speed was 1.25±0.03body lengthss−1 and cost of transport was 3.39±0.17mg O2 kg−1min−1, averaged across the three detected fish. Acceleration transmitters can be effectively used to remotely evaluate fine-scale behavior and estimate energy consumption of adult Pacific salmon throughout their homeward spawning migration.

Temperature Drift Compensation Algorithm Based on BP and GA in Quartzes Flexible Accelerometer

For the purpose of reducing the drift of the Quartzes Flexible accelerometer outputs in different temperatures, an improved BP algorithm based on GA (Genetic Algorithm) for temperature drift compensation of Quartzes Flexible accelerometer is studied in this paper. Based on the theory analysis and the simulation, the GA model has less training steps and better fitting precision compared with BP Neural Network. The results show that this method on temperature drift compensation of quartz flexible accelerometer has achieved good effect.

The Effect of Anatomical Placement and Trunk Adiposity on the Reliability and Validity of Triaxial Accelerometer Output During Treadmill Exercise

Accelerometers are commonly used to quantify physical activity. There is no accordance regarding the most suitable attachment site. This study assessed the reliability and validity of accelerometer output (PAC) from 2 placements. 26 females (age 20.4 ± 1.3 years, body mass 62.7 ± 6.8 kg) twice performed a 16-minute treadmill protocol comprising 4 stages (4, 5, 8, 10 km·hr(-1)) and oxygen uptake (VO2) was calculated. Participants wore an accelerometer at the hip and lower back. Skinfold thickness was measured at 8 sites. Reliability was assessed using coefficients of variation (CVintra). Interactions between placement, velocity and PAC (counts·5s(-1)) were assessed using analysis of covariance. PAC-VO2 associations were assessed using multiple regression. Hip and back placements returned similar reliability (CVintra = 3.0% and 2.8% respectively). Hip PAC were higher (P < .01) during walking with no differences observed during running. Indices of adiposity were related to hip PAC. Regression revealed hip and back PAC as significant predictors of VO2. Back PAC was the least variable. Hip skinfold thickness explained 15% additional variance in VO2 to PAC with reduced standard error. The lower back is a more suitable accelerometer placement for young, active females during treadmill exercise.

Pedometer protocols for measuring physical activity: An examination of reactivity, tampering and perceptions among adolescents

Introduction: Little is known about reactivity and tampering in pedometer-based research in adolescents. The primary aim of this study was to investigate adolescents’ reactivity and tampering while wearing pedometers by comparing different monitoring protocols to accelerometer output. A secondary aim was to explore adolescents’ perceptions and experiences regarding objective monitoring devices.

Research on Signal Processing Circuits of Ring Oscillator Accelerometer

In this paper, the basic principle of the ring oscillator accelerometer has been analysed. According to the characteristics of low-frequency signal of ring oscillator accelerometer output, the methods to measure the low frequency of the sensor output signal by measure period is proposed and simulated the comparator circuit. Finally, we design and simulate all measure circuits and the results and theory in line with the good.

Design of a Digital Tower Tilting Measuring Instrument Based on MEMS Sensor

Abstract: This article introduces a new digital inclinometer . It is designed by the combination of MEMS sensors and LPC1114 which is popular with low-power, low-cost 32-bit cortex-M0 embedded microprocessor on the market. Kalman fitter the Digital signal output of MEMS accelerometer and gyroscope . Then calculate the inclination angle in degrees. Finally, transfers data to a remote server. The instrument is low cost, fast signal processing speed, and solar green energy. It has a small size, light weight, high accuracy and high precision. Then, it can be widely used in the tower tilting real-time monitoring of electricity, buildings, bridges and gravity reference system.

Accelerometers in collars identify behavioral states in captive African elephants Loxodonta africana

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 18:255-263 (2012) - DOI: https://doi.org/10.3354/esr00452 Accelerometers in collars identify behavioral states in captive African elephants Loxodonta africana Joseph Soltis1,*, Rory P. Wilson2, Iain Douglas-Hamilton3,4, Fritz Vollrath3,4, Lucy E. King3, Anne Savage1 1Education and Science, Disney’s Animal Kingdom®, Florida 32830, USA 2Biological Sciences, Institute of Environmental Sustainability, Swansea University, Swansea SA2 8PP, UK 3Save the Elephants, PO Box 54667, Nairobi 00200, Kenya 4Animal Behaviour Research Group, Department of Zoology, University of Oxford, Oxford OX1 2JD, UK *Email: joseph.soltis@disney.com ABSTRACT: Accelerometers are motion-detection devices that, when attached to animals, are capable of detecting body orientation, overall activity levels, and specific behavior patterns. We deployed accelerometers in order to study the hypothesis that accelerometer output would allow us to distinguish between 4 behavior patterns in 3 adult female African elephants Loxodonta africana at Disney’s Animal Kingdom®, Florida, USA. Tri-axial accelerometer data loggers were attached to the tops of collars worn around the elephants’ necks. Behavior was documented on video while the accelerometer output was stored on the data logger. Feeding, bathing, and walking behaviors were recorded in all 3 subjects, while swaying behavior could be recorded in only 1 subject. Data in the 3 physical dimensions (sway, surge, and heave) were analyzed in terms of overall magnitude of movement (dynamic acceleration) and in terms of the periodicity of movement. When classifying accelerometer data of unlabeled origin to the correct behavioral state, overall success ranged from 70 to 91%. Bathing was sometimes confused with feeding and walking, but feeding, walking, and swaying were easily distinguished from each other. These results show that data from accelerometers can distinguish an elephant’s behavioral states, and thus may be used to monitor elephant behavior remotely. Such devices could be deployed for a variety of purposes, ranging from monitoring elephant activity in zoos to an early-warning system that could alert the authorities when wild elephants are being illegally hunted. KEY WORDS: Behavior measurement · Accelerometry · Elephant management Full text in pdf format PreviousNextCite this article as: Soltis J, Wilson RP, Douglas-Hamilton I, Vollrath F, King LE, Savage A (2012) Accelerometers in collars identify behavioral states in captive African elephants Loxodonta africana . Endang Species Res 18:255-263. https://doi.org/10.3354/esr00452 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 18, No. 3. Online publication date: September 28, 2012 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2012 Inter-Research.

Random error modelling and compensation of accelerometer in airborne remote sensing stabilized platform

This paper studies the impact of the accelerometer output error on the levelling accuracy in levelling mode of the airborne remote sensing stabilized platform. On the basis that the accelerometer output signal is non-stationary, a non-stationary time series model of ARIMA(3,0,1) is established, with which an adaptive Kalman filter is designed. In the Kalman filter, an online correction method for the forgetting factor based on real-time measurements is presented, achieving the automatic adjustment of the Kalman filter gain. The model of the accelerometer and the adaptive Kalman filter are applied to the airborne remote sensing stabilized platform principle prototype made by our research group. On one hand, the results show that the model is fit for the accelerometer. On the other hand, it is noted that the new filter has improved the measurement accuracy of the accelerometer, depressed the oscillations of the levelling progress of the platform and reduced the steady-state error of the platform. The levelling performance of the stabilized platform is efficiently improved after all these work.

A Cross-Sectional Study of the Relationship between Cortical Bone and High-Impact Activity in Young Adult Males and Females

Context:The factors that govern skeletal responses to physical activity remain poorly understood.Objective:The aim of this study was to investigate whether gender or fat mass influences relationships between cortical bone and physical activity, after partitioning accelerometer outputs into low (0.5–2.1 g), medium (2.1–4.2 g), or high (>4.2 g) impacts, where g represents gravitational force.Design/Setting:We conducted a cross-sectional analysis in participants from the Avon Longitudinal Study of Parents and Children.Participants:We studied 675 adolescents (272 boys; mean age, 17.7 yr).Outcome Measures:We measured cortical bone parameters from peripheral quantitative computed tomography scans of the mid-tibia, adjusted for height, fat mass, and lean mass.Results:High-impact activity was positively associated with periosteal circumference (PC) in males but not females [coefficients (95% confidence intervals), 0.054 (0.007, 0.100) and 0.07 (−0.028, 0.041), respectively; showing sd change per doubling in activity]. There was also weak evidence that medium impacts were positively related to PC in males but not females (P = 0.03 for gender interaction). On stratifying by fat mass, the positive relationship between high-impact activity and PC was greatest in those with the highest fat mass [high impact vs. PC in males, 0.01 (−0.064, 0.085), 0.045 (−0.040, 0.131), 0.098 (0.012, 0.185), for lower, middle, and upper fat tertiles, respectively; high impact vs. PC in females, −0.041 (−0.101, 0.020), −0.028 (−0.077, 0.022), 0.082 (0.015, 0.148), P = 0.01 for fat mass interaction]. Similar findings were observed for strength parameters, cross-sectional moment of inertia, and strength-strain index.Conclusions:In late adolescence, associations between high-impact activity and PC are attenuated by female gender and low body fat, suggesting that the skeletal response to high-impact activity is particularly reduced in young women with low fat mass.

Wireless Beach Profiler

Abstract Gutierrez, J.; Gomez-Munoz, V.; Villa-Medina, F., and Porta-Gandara, M.A., 2012. Wireless beach profiler. A wireless beach profiler was designed using a vertically aligned accelerometer to estimate slopes along several points of the beach. The accelerometer output from each point was measured as a tilt angle by a microcontroller and transmitted to a personal digital assistant via a radio frequency wireless link. The digital assistant was used to store the data file for subsequent analysis. The device was mounted on a metal board and pulled along a perpendicular path to the beach, where the sampling points were located. The system included a global positioning system (GPS) receiver to record the actual path traversed. The results of this proposed profiling system were compared with an electronic distance meter and with the Emery method. The wireless beach profiler was also evaluated on a robotic vehicle to automate the process. Results showed that this profiler system is a reliable alternative bec...

Improved Iterative Calibration for Triaxial Accelerometers Based on the Optimal Observation

This paper presents an improved iterative nonlinear calibration method in the gravitational field for both low-grade and high-grade triaxial accelerometers. This calibration method assumes the probability density function of a Gaussian distribution for the raw outputs of triaxial accelerometers. A nonlinear criterion function is derived as the maximum likelihood estimation for the calibration parameters and inclination vectors, which is solved by the iterative estimation. First, the calibration parameters, including the scale factors, misalignments, biases and squared coefficients are estimated by the linear least squares method according to the multi-position raw outputs of triaxial accelerometers and the initial inclination vectors. Second, the sequence quadric program method is utilized to solve the nonlinear constrained optimization to update the inclination vectors according to the estimated calibration parameters and raw outputs of the triaxial accelerometers. The initial inclination vectors are supplied by normalizing raw outputs of triaxial accelerometers at different positions without any a priori knowledge. To overcome the imperfections of models, the optimal observation scheme is designed according to some maximum sensitivity principle. Simulation and experiments show good estimation accuracy for calibration parameters and inclination vectors.

Prediction of Gap Asymmetry in Differential Micro Accelerometers

Gap asymmetry in differential capacitors is the primary source of the zero bias output of force-balanced micro accelerometers. It is also used to evaluate the applicability of differential structures in MEMS manufacturing. Therefore, determining the asymmetry level has considerable significance for the design of MEMS devices. This paper proposes an experimental-theoretical method for predicting gap asymmetry in differential sensing capacitors of micro accelerometers. The method involves three processes: first, bi-directional measurement, which can sharply reduce the influence of the feedback circuit on bias output, is proposed. Experiments are then carried out on a centrifuge to obtain the input and output data of an accelerometer. Second, the analytical input-output relationship of the accelerometer with gap asymmetry and circuit error is theoretically derived. Finally, the prediction methodology combines the measurement results and analytical derivation to identify the asymmetric error of 30 accelerometers fabricated by DRIE. Results indicate that the level of asymmetry induced by fabrication uncertainty is about ±5 × 10−2, and that the absolute error is about ±0.2 μm under a 4 μm gap.

Detection of (In)activity Periods in Human Body Motion Using Inertial Sensors: A Comparative Study

Determination of (in)activity periods when monitoring human body motion is a mandatory preprocessing step in all human inertial navigation and position analysis applications. Distinction of (in)activity needs to be established in order to allow the system to recompute the calibration parameters of the inertial sensors as well as the Zero Velocity Updates (ZUPT) of inertial navigation. The periodical recomputation of these parameters allows the application to maintain a constant degree of precision. This work presents a comparative study among different well known inertial magnitude-based detectors and proposes a new approach by applying spectrum-based detectors and memory-based detectors. A robust statistical comparison is carried out by the use of an accelerometer and angular rate signal synthesizer that mimics the output of accelerometers and gyroscopes when subjects are performing basic activities of daily life. Theoretical results are verified by testing the algorithms over signals gathered using an Inertial Measurement Unit (IMU). Detection accuracy rates of up to 97% are achieved.

Measuring and Validating Physical Activity and Sedentary Behavior Comparing a Parental Questionnaire to Accelermeter Data and Diaries

Accurately measuring children's physical activity and their sedentary behavior is challenging. The present study compared 189 parental responses to a questionnaire surveying physical activity and sedentary behavior of children aged 6-14 years, to accelerometer outputs and time activity diaries for the same group. Responses were analyzed taking age, sex and maternal education into account. Correlation coefficients between questionnaire reports and accelerometer-based physical activity across all age groups were acceptable (up to r = .55). Yet, adjustment for age markedly attenuated these associations, suggesting concomitant influences of biological and behavioral processes linked to age. The comparisons of general time indications in the questionnaire with 24h-diary records suggested that parents tended to under- and over-report single activities, possibly due to social desirability. We conclude that physical activity questionnaires need to be designed for specific age groups and be administered in combination with objective measurements.

Transfer Function Compensation in Gyroscope-Free Inertial Measurement Units for Accurate Angular Motion Sensing

Gyroscope-free inertial measurement units have been gaining popularity in applications such as motion sensing of hand-held microsurgical instruments. Various accelerometer placement configurations have been proposed in the past. However, the effect of non-identical transfer functions of accelerometers on the accuracy of angular motion sensing has been underestimated and never been taken into consideration. In this paper, significant effect of different phases at different accelerometer outputs due to non-identical transfer functions on the accuracy is highlighted, and a method is proposed to make the transfer functions of all the accelerometers identical. Effectiveness of the method is confirmed with an experiment using ADXL-203 accelerometers.

Quadratic Mode Shape Components From Ground Vibration Testing

Points on a vibrating structure generally move along curved paths rather than straight lines. For example, the tip of a cantilever beam vibrating in a bending mode experiences axial displacement as well as transverse displacement. The axial displacement is governed by the inextensibility of the neutral axis of the beam and is proportional to the square of the transverse displacement; hence the name “quadratic mode shape component.” Quadratic mode shape components are largely ignored in modal analysis, but there are some applications in the field of modal-basis structural analysis where the curved path of motion cannot be ignored. Examples include vibrations of rotating structures and buckling. Methods employing finite element analysis have been developed to calculate quadratic mode shape components. Ground vibration testing typically only yields the linear mode shape components. This paper explores the possibility of measuring the quadratic mode shape components in a sine-dwell ground vibration test. This is purely an additional measurement and does not affect the measured linear mode shape components or the modal parameters, i.e., modal mass, frequency, and damping ratio. The accelerometer output was modeled in detail taking into account its linear acceleration, its rotation, and gravitational acceleration. The response was correlated with the Fourier series representation of the output signal. The result was a simple expression for the quadratic mode shape component. The method was tested on a simple test piece and satisfactory results were obtained. The method requires that the accelerometers measure down to steady state and that up to the second Fourier coefficients of the output signals are calculated. The proposed method for measuring quadratic mode shape components in a sine-dwell ground vibration test seems feasible. One drawback of the method is that it is based on the measurement and processing of second harmonics in the acceleration signals and is therefore sensitive to any form of structural nonlinearity that may also cause higher harmonics in the acceleration signals. Another drawback is that only the quadratic components of individual modes can be measured, whereas coupled quadratic terms are generally also required to fully describe the motion of a point on a vibrating structure.

Implementation of a monolithic capacitive accelerometer in a wafer-level 0.18 µm CMOS MEMS process

This paper describes the design, fabrication and characterization of a complementary metal-oxide-semiconductor (CMOS) micro-electro-mechanical-system (MEMS) accelerometer implemented in a 0.18 µm multi-project wafer (MPW) CMOS MEMS process. In addition to the standard CMOS process, an additional aluminum layer and a thick photoresist masking layer are employed to achieve etching and microstructural release. The structural thickness of the accelerometer is up to 9 µm and the minimum structural spacing is 2.3 µm. The out-of-plane deflection resulted from the vertical stress gradient over the whole device is controlled to be under 0.2 µm. The chip area containing the micromechanical structure and switched-capacitor sensing circuit is 1.18 × 0.9 mm2, and the total power consumption is only 0.7 mW. Within the sensing range of ±6 G, the measured nonlinearity is 1.07% and the cross-axis sensitivities with respect to the in-plane and out-of-plane are 0.5% and 5.8%, respectively. The average sensitivity of five tested accelerometers is 191.4 mV G−1with a standard deviation of 2.5 mV G−1. The measured output noise floor is 354 µG Hz−1/2, corresponding to a 100 Hz 1 G sinusoidal acceleration. The measured output offset voltage is about 100 mV at 27 °C, and the zero-G temperature coefficient of the accelerometer output is 0.94 mV °C−1 below 85 °C.

Prediction of Energy Expenditure From Wrist Accelerometry in People With and Without Down Syndrome

This study examined the relationship between energy expenditure and wrist accelerometer output during walking in persons with and without Down syndrome (DS). Energy expenditure in metabolic equivalent units (METs) and activity-count rate were respectively measured with portable spirometry and a uniaxial wrist accelerometer in 17 persons with DS (age: 24.7±6.9 years; 9 women) and 21 persons without DS (age: 26.3±5.2 years; 12 women) during six over-ground walking trials. Combined groups regression showed that the relationship between METs and activity-count rate differed between groups (p<.001). Separate models for each group included activity-count rate and squared activity-count rate as significant predictors of METs (p≤.005). Prediction of METs appeared accurate based on Bland-Altman plots and the lack of between-group difference in mean absolute prediction error (DS: 17.07%; Non-DS: 18.74%). Although persons with DS show altered METs to activity-count rate relationship during walking, prediction of their energy expenditure from wrist accelerometry appears feasible.

Prediction of energy consumption according to physical activity intensity in daily life using accelerometer

This research aims to accurately predict energy consumption according to physical activity intensity in daily life using an accelerometer. To derive a simple but accurate equation for prediction of correlations between acceleration information and energy consumption according to physical activity intensity, the following practices have been undertaken in this research. First, an experiment has been conducted with accelerometers attached at the waist and wrist. Second, 13 motions in daily life with different physical activity intensities were performed. The experiment was conducted on 20 healthy persons using a respiratory gas analyzer for measurement of actual energy consumption. As a predictive model for energy consumption, a multiple regression equation was developed using accelerometer data and physical information about the subjects. For comparison between single accelerometer attached at the waist and two accelerometers attached at the wrist and waist, the correlation between actual energy consumption and accelerometer output for the former was 0.911 and that for the latter was 0.914, which is not significantly different. This result implied that one accelerometer attached at the waist is practically efficient in terms of prediction of energy consumption. As a result of comparison between a single regression equation without motion classification and several regression equations with inclusive motion classification, it was found that several regression equations showed smaller errors (0.64 vs 0.18). Thus for accurate and practical prediction of energy consumption, it is recommended to use several regression equations with inclusive motion classification and single accelerometer attached at the waist.

Tuneable vibration absorber using acceleration and displacement feedback

This study is concerned with the analysis and design of a tuneable vibration absorber, which is composed by a flexible beam with a clamping block in the middle and two masses symmetrically mounted at the two ends. The free length of the beam is used to accommodate piezoelectric strain actuators. The two masses at the ends are equipped with inertial accelerometers. This arrangement is used to generate two independent acceleration feedback control loops that produce virtual mass effects, which shift the absorbing frequency of the device. Another arrangement is also studied where the two accelerometer outputs are time-integrated twice in order to implement displacement feedback loops that change the beam stiffness to shift the characteristic frequency of the device. The two feedback approaches are first analysed theoretically, using a mobility-impedance model, and then experimentally on a prototype absorber unit. The stability of the feedback loops is studied using the Nyquist criterion in order to estimate the limits on the tuneable range of frequencies which are set by the maximum stable feedback gains. The study indicates that the stability margins for the acceleration feedback loops substantially depend on the application of an appropriate low-pass filter. On the contrary, the implementation of displacement feedback gives better stability margins.