Single-axis Accelerometer Research Articles

Influence of physical activity on the epigenetic clock: evidence from a Japanese cross-sectional study

BackgroundBiological age, especially epigenetic age derived from the epigenetic clock, is a significant measure of aging, considering the differences in aging rates among individuals. The epigenetic clock, a machine learning-based algorithm, uses DNA methylation states to estimate biological age. Previous studies have reported inconsistent associations between physical activity (PA) and the epigenetic clock, especially second-generation clocks such as PhenoAge and GrimAge. This study aimed to clarify this relationship using cross-sectional data from Japanese participants aged 40–69.MethodsWe used two datasets from the Saga J-MICC study, of which 867 samples were available for analysis. DNA methylation data from peripheral blood samples were used to calculate the epigenetic age using the epigenetic clocks PhenoAge and GrimAge. PA and sedentary time were measured using a single-axis accelerometer, while self-reported PA, sedentary time, and covariates were assessed using a self-administered questionnaire. The association between PA or sedentary time and epigenetic age acceleration was assessed using multiple linear regression.ResultsPearson's correlation coefficients between accelerometer-based and self-reported PA variables ranged from 0.09 to 0.20. Multivariable regression analysis showed that accelerometer-based PA and sedentary time were associated with epigenetic age decelerations and accelerations, respectively. However, self-reported PA was not associated with the epigenetic age accelerations.ConclusionsThese results indicate that reducing sedentary time and increasing PA were associated with slowing both PhenoAge and GrimAge, even in East Asian populations with different exercise habits, body shapes, and lifestyles. This study highlights the potential of objective second-generation epigenetic age acceleration as an outcome index for healthcare interventions and clinical applications.

Nanoscale dual-axis accelerometer based on a cross-shaped MIM waveguide structure

This paper details the design and simulation of a dual-axis accelerometer based on the cross-shaped MIM waveguide structure, in which mass blocks are set in the middle of metal sheets inside the resonant cavities as acceleration-sensitive elements. To maintain the balance between the sensitivity and accuracy of the accelerometer, the optimal surface plasmon resonances (SPRs) are discussed to determine the relationship between resonance wavelength and acceleration. Firstly, the performances of two single-axis accelerometers are evaluated within the range of -20 g to 20 g, and the fitting results indicate that the wavelengths of specific SPRs are linearly related to the acceleration. The maximum sensitivities of the x-axis and y-axis accelerometers are 0.15 nm/g and 0.31 nm/g, respectively. After that, a dual-axis accelerometer is designed based on the structural features of the two single-axis accelerometers, achieving the maximum acceleration sensitivity Sa and FOM of 0.16 nm/g and 0.0015g-1 along the x-axis, and 0.30 nm/g and 0.0077g-1 along the y-axis. As a result, this design implements high-precision independent dual-axis acceleration sensing and presents substantial potential for application in diverse nano-scale acceleration sensing fields.

Industrial-Grade MEMS IMU Calibration

The paper is devoted to the development of the calibration method for MEMS-sensors based inertial measurement unit (IMU). The general purpose of this work was to create the industrial-grade MEMS IMU calibration method. The method was supposed to reduce the temperature instability of inertial sensors static signal to a level of 100 °/h for rate sensors and 1 mg of accelerometers. The article provides a general description of the error types and accuracy classes of inertial sensors. The inertial sensors calibration principle using a known inertial impact series and the obtained dependence approximation by the n-th power polynomial is described too. The calibration methods for single axis and triaxial accelerometers and rate sensors using low and high precision stands are considered. Based on the considered materials, the digital inertial sensors calibration method using a triaxial high precision stand was developed. The method includes the ARS calibration over the entire measurement range and accelerometers calibration within the ±1 g range. The inertial module calibration experiment showed that the developed method allows achieving the required output signal stability level of the calibrated product over the temperature range.

Free vibration analysis of reinforced concrete beam using sensor

The current work is free vibration analysis of concrete beams. The test is carried out on five concrete beams of varying foundry sand proportions. The beams are subjected to flexural loading and its crack pattern is studied. The crack width is calculated using image processing technique. Here free vibration response beam is calculated beam is excited using hammer and vibration response is calculated using single axis and tri axial accelerometer sensor. The beam is modeled using FEA software and its natural frequency is calculated, then it is compared with actual frequency obtained from sensors. A study is carried out on variation of actual frequency of damaged beam with respect to crack width. It has been found that as the crack width increases frequency of the beam decreases in y direction. Also actual frequency is effected by distance of sensor from crack sensor location and temperature.

Simulation and analysis of suspension based single axis mems capacitive accelerometer

This paper reports a comparison of different types of springs used in MEMS based capacitive accelerometers. In this work MEMS based Single-axis accelerometers are designed using different Suspension systems. Analysis of the structure is done for resonant frequency of 2kHz. Analytical modeling of the different suspensions is presented for the specified frequency. Stress, displacement and capacitive analysis of the accelerometer is done. The sensitivity of the accelerometer with parallel beam suspension is 70nm/g, 50nm/g for folded beam suspension and 35nm/g for serpentine beam suspension. Hence parallel beam suspension has 0.7 times improved sensitivity than folded beam and 2 times better than serpentine suspension accelerometer. Whereas the stress obtained for folded beam is better than the other two. Hence Parallel beam suspension is preferred for higher sensitivity and accuracy whereas Folded beam suspension is preferred for greater structural stability By comparing these devices, it is concluded that a compromise on certain parameters is required in order meet the requirements. If there is higher displacement sensitivity then there is lower mechanical stability and vice versa. The simulations are carried out using COMSOL Multiphysics.

단축 가속도계의 Pseudo 바이어스 모델을 이용한 필터 기반 차량 속력 추정 알고리즘

This study presents a filter-based vehicle longitudinal speed estimation algorithm with improved accuracy by estimating the accelerometer bias using only a single-axis accelerometer in the section where the odometer reliability is low. Most vehicles use odometers to obtain speed information because odometers can measure speed with high accuracy under normal driving conditions. However, since the typical odometer has a characteristic that depends on the measured revolutions per minute of the vehicle wheel, if a slip situation occurs in which the wheel slides owing to a sudden start and sudden stop, then the odometer outputs an inaccurate speed measurement. To solve this problem, we redefine the sensor error model of the accelerometer attached to the vehicle and propose a method to estimate the attitude and self-bias component, which are error components that have large effects on the accelerometer, through an adaptive lowpass filter. In addition, we propose an approach to apply the zero-velocity update method to improve the accuracy of the estimated speed information by integrating the error-compensated acceleration value based on the filter. To evaluate the performance of the proposed algorithm, an actual vehicle experiment was performed, and the speed estimation results of the odometer disabled area were analyzed. The results confirmed that the accuracy of speed estimation was greatly improved.

The factor of outstanding acceleration in the operation of vehicles

Introduction. Scientific research has established the connection of physical factors of the working environment with the pathology of the musculoskeletal system of vehicle drivers. Outstanding acceleration is one of the operational characteristics of vehicles. Due to the fact this factor to have an adverse effect on the stability of metal structures, it is impossible to exclude its adverse effect on the health of workers. The purpose of the study. Identification and the study of outstanding acceleration, and its connection with the formation of pathology of the musculoskeletal system in workers of the transport industry. Material and methods. Review of domestic and foreign scientific literature, measurement of acceleration indicators during vehicle movement, calculation of risk indicators in accordance with MP 2.2.0085-14 “Assessment and forecast of reliability and occupational risk of drivers of various vehicles”. The research was carried out on the example of railway transport. To measure the outstanding acceleration, a single-axis accelerometer Low Noise 21kHz 100g 1-axis accel (for the X axis), measuring range ± 100 g, and ADXL345BCCZ, a 3-axis (x, y, z) digital accelerometer, ±2 g/±4 g/±8 g/±16g [LGA-14 (3×5)], measuring range ±2g, ±4g, ±8g, ±16g. Results. Employees operating railway transport constantly experience low levels of frontal, unbalanced acceleration during speed gain, braking, as well as sagittal acceleration when the locomotive is moving. Prolonged exposure to the constantly changing intensity and direction of the impact of unbalanced acceleration can cause the formation of pathology in the lumbosacral spine, registered as a disease associated with production, in drivers of vehicles. Calculations of the risk indicators for the formation of pathology revealed risk higher levels in locomotive crews compared to unexposed workers. Limitations. Currently, there are no methods of hygienic assessment of the factor of outstanding acceleration identified as a factor of the occupation environment of workers operating vehicles. Conclusion. The unbalanced acceleration must be identified as a harmful professional factor of the working environment for drivers of vehicles, which, in combination with others, can lead to the formation of production-related pathology. This factor of the working environment needs further study, development of measurement, evaluation, analysis and control methods for it.

Angular Velocity Estimation and Error-Covariance Analysis from Accelerometers Using Least Squares

In this work angular velocity solutions are presented from accelerometers. Two main formulations are presented. The first is based on using multiple vector sets of accelerometers, and the second is based on using multiple single-axis accelerometers. Linear least-squares approaches are derived for both, along with error-covariance expressions for the angular velocity estimates. Nonlinear least-squares approaches are also derived for both, which also provide the Cramér–Rao lower bound as a byproduct. All approaches have a sign ambiguity in the angular velocity solutions, which is resolved using a simple linear Kalman filter. Simulation results are shown to compare the formulations, along with the linear and nonlinear least-squares solutions.

Epigenome-Wide Association Study Identified VTI1A DNA Methylation Associated With Accelerometer-Assessed Physical Activity.

Health benefits of physical activity (PA) may be mediated by DNA methylation alterations. The purpose of the current study was to comprehensively identify CpG sites whose methylation levels were associated with accelerometer-assessed total PA in a general Japanese population. The study participants were from the baseline survey of Saga Japan Multi-institutional Collaborative Cohort. PA was objectively measured by a single-axis accelerometer for 7 d. We used a two-stage strategy. In the discovery stage, we performed a meta-analysis of two epigenome-wide association studies of total PA in 898 individuals (a combination of random sample ( n = 507) and case-control study sample ( n = 391)). Peripheral blood DNA methylation levels were measured using Infinium EPIC or HM450 arrays. In the replication stage, we subsequently examined whether CpG sites significantly associated ( P < 1 × 10 -5 ) with total PA were replicated in another sample ( n = 1711), in which methylation levels were measured by pyrosequencing. A multiple linear regression was performed to determine the cross-sectional association between total PA and methylation levels with adjustment for potential confounders, including body mass index. A fixed-effects model was used in the meta-analysis. Correlations between total PA-associated DNA methylation and several inflammatory markers, such as high-sensitivity C-reactive protein, were also conducted. In the meta-analysis, nine CpG sites were significantly associated with total PA ( P < 1 × 10 -5 ). Among the nine sites, one site cg07030336 (annotated to VTI1A/ZDHHC6 gene) was successfully replicated ( P = 0.009). The current study showed that greater accelerometer-assessed total PA was associated with higher DNA methylation levels at cg07030336 ( VTI1A/ZDHHC6 ) in the general population. In addition, we found a divergent relationship between the methylation levels at cg07030336 and several inflammatory biomarkers.

Comparative Analysis of Physical Activity Detected via an External Accelerometer and Cardiac Implantable Electronic Devices.

BackgroundPhysical activity (PA) has become an important health issue for decades. Cardiovascular implantable electronic devices (CIEDs) have built-in PA-recording functions. We aimed to compare PA measurements using an external accelerometer (ActiGraph GT3X+) and internal accelerometers (Abbott, Biotronik, and Medtronic CIEDs).MethodsThis was a prospective, single-center observational study. The device-measured 7-day average PA was collected, and GT3X+ -measured 7-day average PA was used as the gold-standard, including all daily observations of activity. Pearson’s correlation coefficients were used to compare the correlations between GT3X+ -measured and CIED-measured PA. Bland-Altman plots were used to analyze measurement agreement, and intraclass correlation coefficients were used to analyze reliability.ResultsIn total, 720 patients treated with CIEDs were surveyed between November 2020 and April 2021, 60 of them were analyzed after patient screening by our protocol. Each manufacturer included 20 patients for the final analysis. The CIED-measured PAs of Abbott, Biotronik, and Medtronic were 3.0 ± 1.5, 2.6 ± 1.8, and 3.8 ± 2.5 h per day, respectively; the GT3X+ -measured PAs were 6.9 ± 2.8, 6.0 ± 2.4, and 6.4 ± 2.5 h per day, respectively. Moderate and significant correlations were found in patients using Abbott, Biotronik, and Medtronic CIEDs (r = 0.534, p = 0.015; r = 0.465, p = 0.039; r = 0.677, p = 0.001, respectively). Bland-Altman plots and intraclass correlation coefficients both showed a significant correlation and reliability between the average PA measured by GT3X+ and CIEDs (hours per day).ConclusionAlthough the PA recording function of CIEDs includes a single-axis accelerometer, it has a moderate correlation compared with the triaxial accelerometer of the GT3X+. However, CIEDs seem to underestimate PA for 3–4 h compared to the GT3X+.

Validation of the Lifecorder Plus device for accurate recording of the grazing time of dairy goats

Few portable devices that record grazing time have been tested on goats. The Lifecorder Plus is a commercial device, based on a single-axis accelerometer, that calculates and stores in memory the average activity level (range: 0–9) every 2 min. Previous studies determined that activity levels greater than or equal to 0.5 were specific to grazing, while those less than 0.5 could be considered as other activities. The aims of the present study were to determine the threshold value that minimised the prediction error and to validate the ability of the Lifecorder Plus device to record goat grazing time at vegetative temperate pasture under rotational grazing management. Twenty goats (5 in 2015 and 15 in 2017) were fitted with the Lifecorder Plus on their neck and had access to pasture for 8−12 h/d. The device was evaluated by comparing 2-min visual observations of trained observers to the activity level recorded at the same time by the device, resulting in a total of 187 h of observations. Two analysis methods were used to assess the device’s accuracy: a confusion matrix and the mean squared prediction error. Lifecorder Plus recorded grazing time with 93 % accuracy, 95 % precision, 97 % sensitivity and 73 % specificity. Relative prediction errors calculated at the hour and day scales were low, averaging 0.09 and 0.05 of actual grazing time, respectively. Overall, there was no confusion between grazing and other goat activities. Lifecorder Plus overestimated grazing time by 3%, probably due to other activities of goats (lack of specificity). Placing an additional Lifecorder Plus on a leg may help identify non-grazing activities (e.g. long-duration walking, running) and thus reduce this slight overestimation. No bias due to sward height was detected. In conclusion, for rotationally grazed vegetative temperate pastures, Lifecorder Plus detects grazing activities of goats with high accuracy and precision and is suitable for studying variations in grazing time, particularly at the day scale in small paddocks.

Head Impact Exposure Of A Youth Football Team Over Eight Consecutive Seasons

There is growing evidence for the potential risk of brain injury due to repetitive, subconcussive head impacts in youth football. Despite increased awareness and efforts to reduce head impact exposure (HIE) in this sport, an objective, longitudinal assessment of HIE in youth football is noticeably lacking. PURPOSE: To examine HIE in middle school football players over multiple seasons. METHODS: HIE was evaluated in 94 middle school football players (11-14 yr) who participated in a community youth tackle football program with the same coaching staff over eight consecutive seasons (2012-2019). HIE was assessed using the Head Impact Telemetry System, which utilizes a helmet-mounted array of six single-axis accelerometers to measure head impact frequency, severity (linear and rotational acceleration) and location. Mean head impacts per player per session (HIPS) and median head impact severity measures were compared across seasons. RESULTS: There were 33,519 head impacts registered throughout the eight-year study. Mean practice HIPS and overall HIPS decreased each season, resulting in a 79.4% (10.7 vs. 2.2 HIPS, P < 0.001) and 74.4% (12.5 vs. 3.2 HIPS, P < 0.001) decrease, respectively, from 2012-2019. Mean game HIPS were reduced by 60.6%, with a significant difference observed between 2012-14 and 2015-19 (17.7 ± 0.7 vs. 9.5 ± 2.1 HIPS, P < 0.01). Median linear and rotational acceleration remained relatively unchanged during the study. Head impacts greater than 80 g decreased every season from 103 in 2012 to 11 in 2019. Nine subjects experienced physician-diagnosed concussions during the study, resulting in a concussion rate of 1:3724 head impacts. CONCLUSIONS: Head impacts incurred by youth football players from a community football league decreased considerably over eight seasons, with players in the final year of the study sustaining approximately one-fourth the head impacts per session as players experienced during the first year. The greatest and most consistent decline occurred in practices, though players also had much fewer head impacts in games. While factors associated with observed reductions in head impact exposure were not investigated, these results suggest that coaching and/or player behavior can be modified to greatly reduce the head impact burden and brain injury risk of youth football players.

The Changes of Ergonomic Engine Vibroacoustic Response Regarding Their Development

The article presents the results of research on the vibroacoustic response of internal combustion engines mounted in a vehicle. The vehicles studied belong to popular models, which became available in successive versions. Each group included vehicles of the same model of an older generation (equipped with a naturally aspirated engine) and of a newer generation, including downsized (and turbocharged) engines. Tests in each group were carried out under repeatable conditions on a chassis-load dynamometer. The vibrations were measured using single-axis accelerometers mounted on the steering wheel, engine, and driver’s head restraint mounting. The primary purpose of the study was to verify whether the new generations of vehicles equipped with additional high-speed elements (compressors) generate additional harmonics (especially those within the range potentially affecting travel comfort and human health) and whether there are significant changes in the distribution of spectral power density in the new generations. As the study showed, new generations of vehicles are characterized by a different vibroacoustic response, and the trend of change is the same in each of the families studied.

Aerodynamic characteristics of a free-flight scramjet vehicle in shock tunnel

A multi-component aerodynamic test for an airframe-engine integrated scramjet vehicle model was conducted in the free-piston shock tunnel HIEST. A free-flight force measurement technique was applied to the scramjet vehicle model named MoDKI. A new method using multiple piezoelectric accelerometers was developed based on overdetermined system analysis. Its unique features are the following: (1) The accelerometer’s mounting location can be more flexible. (2) The measurement precision is predicted to be improved by increasing the number of accelerometers. (3) The angular acceleration can be obtained with single-axis translational accelerometers instead of gyroscopes. (4) Through the averaging process of the multiple accelerometers, model natural vibration is expected to be mitigated. With eight model-onboard single-axis accelerometers, the three-component aerodynamic coefficients (Drag, Lift, and Pitching moment) of MoDKI were successfully measured at the angle of attack from 0.7 to 3.4 degrees under a Mach 8 free-stream test flow condition. A linear regression fitting revealed a 95% prediction interval as the measurement precision of each aerodynamic coefficient.Graphical abstract

Quaternion Algorithm for Initial Alignment of Strapdown INS Using the A. N. Tikhonov Regularization Method

For the functioning of algorithms of inertial orientation and navigation of strapdown inertial navigation system (SINS), it is necessary to conduct a mathematical initial alignment of SINS immediately before the operation of these algorithms. An efficient method of initial alignment (not calibration!) of SINS is the method of vector matching. Its essence is to determine the relative orientation of the instrument trihedron Y (related to the unit of SINS sensors) and the reference trihedron X according to the results of measuring the projections of at least two non-collinear vectors of the axes on both trihedrons. We address the estimation of the initial orientation of the object using the method of gyrocompassing, which is a form of vector matching method. This initial alignment method is based upon using the projections of the apparent acceleration vectoraand the absolute angular velocity vectorωof the object in the coordinate systems X and Y. It is assumed that the three single-axis accelerometers and the three gyroscopes (generally speaking, the three absolute angular velocity sensors of any type), which measure the projections of the vectorsaandω, are installed along the axes of the instrument coordinate system Y. If the projections of the same vectors on the axes of the base coordinate system X are known, then it is possible to estimate the mutual orientation of X and Y trihedrons. We are solving the problem of the initial alignment of SINS for the case of a fixed base, when the accelerometers measure the projection gi(i = 1, 2, 3) of the gravity acceleration vectorg, and the gyroscopes measure the projectionsui of the vector u of angular velocity of Earth’s rotation on the body-fixed axes. The projections of the same vectors on the axes of the normal geographic coordinate system X are also estimated using the known formulas. The correlation between the projections of the vectorsuandgin X and Y coordinate system is given by known quaternion relations. In these relations the unknown variable is the orientation quaternion of the object in the X coordinate system. By separating the scalar and vector parts in the equations, we obtain an overdetermined system of linear algebraic equations (SLAE), where the unknown variable is the finite rotation vectorθ, which aligns the X and Y coordinate systems (it is assumed that there is no half-turn of the X coordinate system with respect to the Y coordinate system). Thus, the mathematical formulation of the problem of SINS initial alignment by means of gyrocompassing is to find the unknown vectorθfrom the derived overdetermined SLAE. When finding the vectorθdirectly from the SLAE (algorithm 1) and data containing measurement errors, the components of the vector q are also determined with errors (especially the component of the vectorθ, which is responsible for the courseψof an object). Depending on the pre-defined in the course of numerical experiments values of headingψ, rollϑ, pitchγangles of an object and errors of the input data (measurements of gyroscopes and accelerometers), the errors of estimating the heading angle Δψ of an object may in many cases differ from the errors of estimating the roll Δϑ and pitch Δγ angles by two-three (typically) or more orders. Therefore, in order to smooth out these effects, we have used the A. N. Tikhonov regularization method (algorithm 2), which consists of multiplying the left and right sides of the SLAE by the transposed matrix of coefficients for that SLAE, and adding the system regularization parameter to the elements of the main diagonal of the coefficient matrix for the newly derived SLAE (if necessary, depending on the value of the determinant of this matrix). Analysis of the results of the numerical experiments on the initial alignment shows that the errors of estimating the object’s orientation angles Δψ, Δϑ, Δγ using algorithm 2 are more comparable (more consistent) regarding their order.

Accelerometer-Based Wheel Odometer for Kinematics Determination

Various high budget industries that utilize wheel-based vehicles rely on wheel odometry as an integral aspect of their navigation process. This research introduces a low-cost alternative for typical wheel encoders that are typically used to determine the on-track speed of vehicles. The proposed system is referred to as an Accelerometer-based Wheel Odometer for Kinematics determination (AWOK). The AWOK system comprises just a single axis accelerometer mounted radially at the center of any given wheel. The AWOK system can provide direct distances instead of just velocities, which are provided by typical wheel speedometers. Hence, the AWOK system is advantageous in comparison to typical wheel odometers. Besides, the AWOK system comprises a simple assembly with a highly efficient data processing algorithm. Additionally, the AWOK system provides a high capacity to handle high dynamics in comparison to similar approaches found in previous related work. Furthermore, the AWOK system is not affected by the inherited stochastic errors in micro-machined electro-mechanical systems (MEMS) inertial sensors, whether short-term or long-term errors. Above all, the AWOK system reported a relative accuracy of 0.15% in determining the distance covered by a car.

Cross-Coupling Coefficient Estimation of a Nano-gAccelerometer by Continuous Rotation Modulation on a Tilted Rate Table

Nano- $g$ accelerometers are widely used in space exploration and measurement of the earth’s gravitational field. It is essential to precisely evaluate error effects at high orders such as cross-coupling for applications in a dynamic environment. Nevertheless, it remains challenging to meet the precision requirements using conventional calibration measures. In this article, we propose a method to separate the cross-coupling coefficients of a linear single-axis accelerometer by mounting it on a steadily rotating rate table that is tilted at a fixed deviation angle with respect to the horizontal plane. The gravity component is periodically modulated along the input axis per revolution. Simultaneously, a series of centripetal acceleration is applied along the cross axis in sequence while adjusting the rotation frequency of the rate table by steps. Thus, the cross-coupling coefficient can be separated by its dependence both on the modulated gravity acceleration and the centripetal acceleration. In comparison to the static multipoint angular rotation test on a tilted dividing head, the proposed dynamic modulation method demonstrates improved robustness against corruption from bias drift, with an improved uncertainty. This method to separate the cross-coupling coefficient is suitable for testing high-resolution accelerometers, without requiring high bias stability or sensitive response sustaining at ultralow frequency.

Evaluation of Head and Body Kinematics Experienced During Parachute Opening Shock.

The U.S. Army conducts airborne operations in order to insert soldiers into combat. Military airborne operations are physically demanding activities with a unique loading environment compared with normal duties. A significant amount of research surrounding airborne operations has focused on assessing the incidence and type of associated injuries as well as the potential risk factors for injuries. During parachute opening shock and other high-acceleration events (e.g., fixed wing flight or vehicle crashes), the neck may be vulnerable to injury if inertial loads overcome the voluntary muscular control of the cervical spine and soft tissue structures. A recent epidemiological survey of sport skydivers showed that the neck, shoulders, and back were the most frequently reported sites of musculoskeletal pain. In addition, the survey indicated that wing loading (a measure of the jumper's weight divided by the size of the parachute canopy) was a potential contributing factor for developing musculoskeletal pain. Recently, there have been efforts to measure the severity of parachute opening shock as an additional potential risk factor for injury; however, no studies have measured both head and body accelerations and no studies have measured head or body angular rate during parachute opening shock. The purpose of this study was to measure and characterize the accelerations and angular rates of both the head and body during parachute opening shock as well as investigate potential factors contributing to higher severity opening shock, which may link to the development of musculoskeletal pain or injury. Data were collected from the U.S. Army Parachute Team, The Golden Knights, under an approved Medical Research and Material Command Institutional Review Board protocol. Subjects were instrumented with a helmet- and body-mounted sensor package, which included three angular rate sensors and three single-axis accelerometers each. Data were collected at 2,500 samples per second. Kruskal-Wallis tests were used to determine if helmet-mounted equipment (e.g., cameras), neck length, neck circumference, or wing loading (the ratio of jump weight to the size of the main parachute canopy) affected the accelerations or angular rates of the head or body. A total of 54 jumps conducted by 19 experienced free-fall jumpers were analyzed. For the head, the mean (± SD) resultant accelerations and angular rates were 5.8 (± 1.6) g and 255.9 (± 74.2) degrees per second (deg/s), respectively. For the body, the resultant accelerations and angular rates were 4.3 (± 1.5) g and 181.3 (± 61.2) deg/s, respectively. A wing loading above 1.4 pounds per square foot (lb/ft2) was found to have a significant effect on head (P = .001) and body (P = .001) resultant acceleration as well as body angular rate about the Y-axis (P = .001). There is evidence to suggest that wing loading has an influence on individual head and body resultant accelerations. However, no significant effects were found for the other variables (e.g., neck length and circumference, helmet-mounted equipment, etc.). Future research should focus on identifying additional factors that result in changes in accelerations and angular rates of the head and body during parachute opening shock events.

On the Accuracy of Fault Diagnosis for Rolling Element Bearings Using Improved DFA and Multi-Sensor Data Fusion Method.

Rolling element bearings are widely employed in almost every rotating machine. The health status of bearings plays an important role in the reliability of rotating machines. This paper deals with the principle and application of an effective multi-sensor data fusion fault diagnosis approach for rolling element bearings. In particular, two single-axis accelerometers are employed to improve classification accuracy. By applying the improved detrended fluctuation analysis (IDFA), the corresponding fluctuations detrended by the local fit of vibration signals are evaluated. Then the polynomial fitting coefficients of the fluctuation function are selected as the fault features. A multi-sensor data fusion classification method based on linear discriminant analysis (LDA) is presented in the feature classification process. The faults that occurred in the inner race, cage, and outer race are considered in the paper. The experimental results show that the classification accuracy of the proposed diagnosis method can reach 100%.

Human-Inspired Haptic Perception and Control in Robot-Assisted Milling Surgery.

Bone milling is one of the most widely used and high-risk procedures in various types of surgeries, and it is important to be noted that the experienced surgeon can perform such an operation safely. The objective of this article is to enhance the safety of the robot-assisted milling operation with the inspiration of human haptic perception. The emergence, coding and perception of the human haptic are introduced. Following this, a single axis accelerometer that measures the vibration of the surgical power tool is mounted in the robot arm, and the recorded acceleration signal is encoded as parallel stream of binary data. The data are subsequently inputted to the Hopfield network so as to identify the milling state. Inspired by human inference procedure, the fuzzy logic controller is introduced to control the robot to track the desired state when performing bone milling operations. A real-time implementation of the proposed method on a digital signal processing is also described. The experimental results in milling porcine spines prove that the robot accurately discriminates different milling states even when the additive noise is serious, and the safe motion control of the robot is also realized.