Root Mean Square Acceleration Research Articles

A Mobile Phone-Based Gait Assessment App for the Elderly: Development and Evaluation.

BackgroundGait disorders are common among older adults. With an increase in the use of technology among older adults, a mobile phone app provides a solution for older adults to self-monitor their gait quality in daily life.ObjectiveThis study aimed to develop a gait-monitoring mobile phone app (Pocket Gait) and evaluate its acceptability and usability among potential older users.MethodsThe app was developed to allow older adults to track their gait quality, including step frequency, acceleration root mean square (RMS), step regularity, step symmetry, and step variability. We recruited a total of 148 community-dwelling older adults aged 60 years and older from two cities in China: Beijing and Chongqing. They walked in three ways (single task, dual task, and fast walking) using a smartphone with the gait-monitoring app installed and completed an acceptability and usability survey after the walk test. User acceptability was measured by a questionnaire including four quantitative measures: perceived ease of use, perceived usefulness, ease of learning, and intention to use. Usability was measured using the System Usability Scale (SUS). Interviews were conducted with participants to collect open-ended feedback questions.ResultsTask type had a significant effect on all gait parameters, namely, step frequency, RMS, step variability, step regularity, and step symmetry (all P values <.001). Age had a significant effect on step frequency (P=.01), and region had a significant effect on step regularity (P=.04). The acceptability of the gait-monitoring app was positive among older adults. Participants identified the usability of the system with an overall score of 59.7 (SD 10.7) out of 100. Older adults from Beijing scored significantly higher SUS compared with older adults from Chongqing (P<.001). The age of older adults was significantly associated with their SUS score (P=.048). Older adults identified improvements such as a larger font size, inclusion of reference values for gait parameters, and inclusion of heart rate and blood pressure monitoring.ConclusionsThis mobile phone app is a health management tool for older adults to self-manage their gait quality and prevent adverse outcomes. In the future, it will be important to take factors such as age and region into consideration while designing a mobile phone–based gait assessment app. The feedback of the participants would help to design more elderly-friendly products.

Reach on damping control and stability analysis of vehicle with double time-delay and five degrees of freedom

Suspension system is one of the important parts of a vehicle, which is used to buffer the impact of uneven road to the body and passengers, so the suspension system has an important impact on the safety and ride comfort of the vehicle. In order to improve the safety and comfort of passengers and vehicles, in this paper a five-degree-of-freedom half car model is established, and the uncertainty of the model and the time-delay of the control are considered. The dynamic response of vehicle body acceleration root mean square, passenger acceleration root mean square, displacement root mean square and vehicle body pitch acceleration root mean square are selected as optimization objectives. The time-delay control parameters are determined by chaos particle swarm optimization algorithm. The time-delay stability of the suspension control system is analyzed by frequency-domain scanning method to ensure the stability of the time-delay control system. Finally, by establishing the simulation model of the active suspension system with double time-delay feedback control, the response characteristics of the suspension system with double time-delay active feedback control to simple harmonic excitation and random excitation input are analyzed. The results show that under the premise of ensuring the system stability, the active suspension system with double time-delay feedback control has good and obvious controlling and damping effect on the body and seats.

Dynamic optimization design of the suspension parameters of car body-mounted equipment via analytical target cascading

Under dynamic conditions, the dynamic force between the suspended equipment and the car body is substantially increased. This increase not only affects the ride comfort but also substantially raises the likelihood of fatigue damage to the suspended equipment. A multiobjective analytical target cascading (ATC) optimization is proposed to improve the ride comfort of high-speed trains and reduce the vibration of the suspended equipment. A mathematical simulation model of the vehicle equipment system is established, and the acceleration frequency-response function expression of the car body and the suspension system is obtained. The comfort index of the car body and the acceleration root mean square (RMS) of the suspended equipment are calculated by combining the German vertical irregular track spectrum and the comfort filter function. Meanwhile, the ATC method is used to optimize the car body comfort index and the acceleration RMS of the underframe suspended equipment. Then, the availability of the optimization method is evaluated via numerical simulation. Compared with the original suspension scheme of the underframe equipment, when the running speed of the vehicle is 300 km/h, the RMS value of the vibrational acceleration of the underframe equipment after optimization decreases by 19.9 %, and the ride comfort indexes at the car body center and above the front and rear bogies are improved by 6.4 %, 0.1 %, and 1.1 %, respectively. Simulation results demonstrate that ATC optimization can improve the railway vehicle ride comfort and reduce the vibration of the suspended equipment. This paper provides a new approach to the suspension parameter design of equipment.

Buffeting response of long-span bridges considering uncertain turbulence parameters using the environmental contour method

Full-scale monitoring of the Hardanger Bridge has revealed significant turbulence-induced variability in the measured acceleration response. In this paper, a probabilistic model is used to describe the uncertain turbulence parameters, and the environmental contour method is used to investigate the long-term root-mean-square (RMS) response of the Hardanger Bridge. The results show that turbulence-induced variability has a significant impact on the bridge girder section moments. It is also interesting that the critical combination of environmental parameters does not necessarily involve the maximum mean wind velocity. By using the environmental contour method to account for turbulence uncertainty, the scattered acceleration RMS response measurements from the Hardanger Bridge are successfully eclipsed by 100-year return period response estimates, showing vast improvements compared with the traditional design methodology. The investigations presented in this paper show that the environmental contour method can be used to improve the accuracy and reduce the uncertainty in buffeting response calculations for long-span bridge design.

Tuned mass dampers in wind response control of wind turbine with soil-structure interaction

The efficiency of tuned mass dampers (TMDs) in along-wind response mitigation of a wind turbine with consideration of blade coupling and soil-structure interaction (SSI) is investigated. The wind turbine tower is modeled as a multi-degree of freedom (MDOF) with three blades are connected as a MDOF system to the tower. The along-wind drag forces are generated using Shinozuka method. The effect of SSI is considered using frequency independent parameters. The equation of motion for the coupled system is numerically solved in time domain using the Newmark Beta method. In order to observe the changes in response of the system, the blades are subjected to rotating wind field to include the effects of the blade-tower interaction and rotor movement. The peak displacement, peak acceleration, root mean square (RMS) displacement, RMS acceleration, and power spectral density (PSD) of the wind turbine are the response quantities considered for comparative studies. Single TMD (STMD) and distributed multiple TMDs (d-MTMDs) are used to mitigate the wind response of the tower. Parametric studies are conducted to find the most suitable parameters (such as mass ratio, frequency bandwidth, and damping ratios) of the TMD schemes to increase the effectiveness of the strategy in the mitigation of the wind response of wind turbine with/without consideration of SSI. It is concluded that wind response of the wind turbine is amplified with inclusion of the SSI, blade-tower interaction, and rotor movement. In addition, it is concluded that the d-MTMDs are more effective and robust in wind response control of the wind turbine as compared to the STMD.

Accelerometer Measurement of Trunk Lateral Fluctuation During Walking Following Total Knee Arthroplasty in Patients With Osteoarthritis.

This study aimed to clarify the effect of total knee arthroplasty (TKA) on trunk fluctuation and regularity of gait in patients with knee osteoarthritis by an accelerometer. The participants included 18 patients with knee osteoarthritis undergoing TKA. The gait at a comfortable velocity was assessed pre- and post-TKA by a triaxial accelerometer attached to the neck and lumbar regions. Measurement post-TKA was performed 4 weeks after surgery. Trunk fluctuation was estimated by the root mean square (RMS) of acceleration and RMS ratio (the ratio of RMS in each direction to the total RMS). Regularity of gait was estimated using the autocorrelation function. The results showed that TKA significantly decreased the RMS ratio in mediolateral acceleration of the neck and lumbar regions and reduced gait regularity. TKA appears to reduce compensatory trunk motion through the improvement of knee function. An assessment of trunk fluctuation using an accelerometer is useful for the clinical assessment of patients with knee osteoarthritis pre- and post-TKA.

Analysis of Vibration Harvesting Properties and Fracturing Structures of Soapberry (Sapindus Mukorossi)

HighlightsAnalyzing the fruit removal force and harvesting time of Sapindus fills a gap of Sapindus research.A dual excitation vibration method for harvesting Sapindus and the best harvesting parameters were obtained.The microstructure of the different fracturing locations was analyzed for the first time. Abstract.To address the issue of labor intensity in the harvest of Sapindus fruit, it is necessary to understand the harvesting properties of Sapindus mukorossi. In this study, a fruit removal force (FRF) test platform was used to analyze the relationship between the FRF and maturation time. An eccentric vibration harvesting test was conducted to obtain the frequency, acceleration, and other parameters of the Sapindus tree. According to the different falling locations of fruit, the fracturing locations were observed by a scanning electron microscope (SEM). The results revealed that the optimal time (9 to 12 November) to harvest is in the middle of the harvest period. Additionally, the shear force from 1.0N to 5.2 N was less than the tensile force from 2.7 to 10.2 N. Therefore, back and forth swinging is the major fracturing form of the fruit. Moreover, dual excitation is preferable to single-point excitation, and the acceleration root mean square (RMS) of the dual excitation was two to three times the acceleration RMS of single point excitation. The harvesting efficiency of dual excitation was 92.3% at 20 Hz. Additionally, there existed four fracturing locations for harvested fruit, as the frequency increased. Furthermore, the fracturing in the ear and stem was the most important form of fracturing, and microscopic observations revealed that it had a thinner and tidier cell wall and cell cavity. Keywords: Sapindus, Fruit removal force, Vibration, Microstructure.

Design and Optimization of Vibration Isolation System for Spacecraft Transport Package Box

The damping effect of vibration isolation system for spacecraft transport package box is directly associated with superior or inferior mechanical environment for spacecraft transportation. In this Article, the design process and program for vibration isolation system for spacecraft transport package box were introduced first; followed by analysis on excitation and response during spacecraft transportation by train; finally, an optimization program of vibration isolation system applicable to current working conditions for transportation was given. The results showed that: the frequency of railway road spectrum excitation was concentrated at 1.8Hz and 6.2Hz, indicating that the current vibration isolation system for package box did not have better damping effect. After reducing first-order inherent frequency by about 3Hz, acceleration root mean square may reduce by 40%.

Quantitative Research on Contribution Degree of Vibration Affecting Factors of Vehicle Suspension System Based on Robustness Analysis

Suspension system is the key component affecting vehicle ride comfort and finding out the main factors affecting suspension system vibration is the precondition of controlling suspension system vibration and improving vehicle comfort. Based on the principle of robustness analysis, the robustness analysis process of suspension system vibration influencing factors is constructed, in order to solve the problem, the three levels of front suspension stiffness, front suspension damping, rear suspension stiffness and rear suspension damping are selected, the experiment design scheme is adopted, power Spectrum of Class A road is used as input excitation source for suspension system simulation, the weighted acceleration root mean square simulation experiment of suspension system vibration under the influence of multiple factors is carried out.

Cutting data effect on machine tool vibrational state and surface roughness when machining

The article is devoted to the study of vibration processes of metal-removal equipment. In the course of the study, the dynamic phenomena arising in the metal processing in this complex dynamic system have been investigated for the purpose of further control of cutting modes that minimize the accompanying oscillations and vibrations. This article presents the results of studying the dependence of the roughness parameters on the vibration of the spindle assembly and processing modes in the milling operation. Planning techniques and experimental statistic were used in our investigation. The dependence of vibration acceleration root-mean square parameters (RMS parameters) on cutting set modes was determined. Monitoring of vibration parameters when machining centres operating allows improving the quality of parts processing and preventing expensive machine operating under dangerous dynamic load.

Ride Comfort Analysis and Multivariable Co-Optimization of the Commercial Vehicle Based on an Improved Nonlinear Model

The performance of a suspension system is affected by the behavior and posture of its components. However, published studies usually conduct this research using the based-equivalent model without considering the characteristic curves or postures. In this paper, an improved ride comfort model that considers three nonlinearities in suspensions is first developed, and this model is validated through experimental results and demonstrates good accuracy. Then, the dynamic response is presented to investigate the effects of multilevel suspension parameters and nonlinear factors on ride comfort, and it is concluded that the front chassis suspension is the most significant system for ride comfort. Next, a multivariable co-optimization method based on the improved model is proposed to obtain more accurate optimized results that are more suitable for automotive applications. Subsequently, a multiobjective genetic algorithm (MGA) is applied to obtain the Pareto solution set. Furthermore, comparing the RMS value before and after optimization shows an obvious reduction, with averages of 19.7%, 17.8%, and 12.0% for the weighted root mean square (RMS) of the driver seat acceleration and the RMS of the working spaces of the front chassis suspension and the rear chassis suspension, respectively. Finally, the results are also verified by experiments, indicating that the improved ride comfort model and the multivariable co-optimization method are feasible and practical.

118 Use of Smart Wearable Devices for Gait Assessment Among Older Chinese

Abstract Introduction This study used smart bracelets and smartphones for gait assessment and analysis. Method Two hundred and twenty-eight older Chinese (mean age 69.3 ± 7.5 years) participated in this study. Participants wore either a smartphone or smart bracelet on their lower back while performing the gait test. They walked at a comfortable speed, at a comfortable speed and serially subtracting by three, and at a fast speed. This study measured gait parameters including speed, step frequency, acceleration root mean square (RMS), step regularity, symmetry and variability. Older adults were classified into pre-frail and non-frail groups based on the FRAIL SCALE (Kan et al., J Nutr Health Aging, 2008, 12, 29–37). We interviewed twenty-eight participants and three medical professionals and developed a smart app for gait assessment. Results It is fast and convenient to use smart wearable devices for gait assessment and analysis. The average speed (1.27m/s) of older Chinese seemed faster compared with older adults from literatures (Capistrant et al., Journal of the American Geriatrics Society, 2014, 62(2), 329-335). Acceleration RMS was correlated with speed (Pearson r = .65–.76, p &amp;lt; .001) and could be a proxy of speed. Pre-frail older adults had significantly decreased speed, RMS, and step regularity compared with non-frail counterparts (ps &amp;lt; .05); step frequency, RMS, regularity, symmetry and variability were significantly different between walking types (ps &amp;lt; .001). The smart app records gait data of 30 seconds and generate a real-time gait assessment report including step frequency, RMS, regularity, symmetry and variability after the gait test. Overall, the acceptability from older adults is positive with participants indicating the app was easy to use and useful. Conclusion The application is a useful tool for older Chinese to track their gait quality in home care.

Fatigue-Related Changes in Running Gait Patterns Persist in the Days Following a Marathon Race.

The risk of experiencing an overuse running-related injury can increase with atypical running biomechanics associated with neuromuscular fatigue and/or training errors. While it is important to understand the changes in running biomechanics within a fatigue-inducing run, it may be more clinically relevant to assess gait patterns in the days following a marathon to better evaluate the effects of inadequate recovery on injury. To use center of mass (CoM) acceleration patterns to investigate changes in running patterns prior to (PRE) and at 2 (POST2) and 7 (POST7) days following a marathon race. Pre-post intervention study. A 200-m oval track surface. Seventeen recreational marathon runners (10 females, age = 34.2 [5.67]y; 7 males, age = 47.41 [15.32]y). Marathon race. An inertial measurement unit was placed near the CoM to collect triaxial acceleration data during overground running for PRE, POST2, and POST7 sessions. Twenty-two features were extracted from the acceleration waveforms to characterize different aspects of running gait. Lower-limb musculoskeletal pain was also recorded at each session with a visual analog scale. At POST2, runners reported higher self-reported pain and exhibited elevated peak mediolateral acceleration with an increased mediolateral ratio of acceleration root mean square compared with PRE. At POST7, pain was reduced and more similar to PRE, with runners demonstrating increased stride regularity in the vertical direction and decreased peak resultant acceleration. The observed changes in CoM motion at POST2 may be associated with atypical running biomechanics that can translate to greater mediolateral impulses, potentially increasing the risk of injury. This study demonstrates the use of an accelerometer as an effective tool to detect atypical CoM motion for runners due to fatigue, recovery, and musculoskeletal pain in real-world environments.

Development and validation of kurtosis response spectrum analysis for antivibration packaging design taking into consideration kurtosis

In current antivibration packaging designs, transport vibrations are generally assumed to be Gaussian random vibrations, and the cushioning material is designed so that the acceleration root mean square (RMS) transmitted to a product is low. However, transport vibrations are often non‐Gaussian random vibrations, and therefore, it is necessary to carry out antivibration packaging design, taking into consideration the non‐Gaussianity characteristics and acceleration RMS of the transport vibrations. In this study, a kurtosis response spectrum was proposed, which is an antivibration packaging design index, taking into account the non‐Gaussianity of transport vibrations. A kurtosis response spectrum is a plot of the kurtosis of the acceleration response for a series of single degree of freedom (SDOF) systems to the base acceleration input, assuming that the packaged product is the SDOF system. The kurtosis response spectrum was applied to the actual transportation data, and the results confirmed that the kurtosis of product response acceleration is different, depending on the natural frequency of the packaged product. Experiments were conducted using a dummy packaged product, and the experimental results showed good agreement with those of the kurtosis response spectrum analysis. It can be concluded that the kurtosis response spectrum is useful to clarify the effect of natural frequency on the kurtosis response. By referring to the kurtosis response spectrum, packaging engineers can obtain the necessary information to perform antivibration packaging design, taking into account the non‐Gaussianity of transport vibrations.

Discrete Element Method Analysis of the Impact Forces on a Garlic Bulb by the Roller of a Garlic Harvester

The discrete element method can be used to simulate particle systems and identify forces acting on a particle, but the suitability of using simulation for the modeling of garlic is undetermined. This study was conducted to evaluate the feasibility of using the EDEM program as a simulation tool for garlic bulbs in a garlic harvester. Simulations were compared with experimental collisions between a bulb and the roller of a garlic harvester. In the collision tests, the behavior and impact of an artificial garlic were observed with a high-speed camera and an accelerometer. The simulated positions and accelerations of the garlic were obtained in EDEM using the same parameters as those of the experiment. The impacts of the garlic were compared in terms of the root mean square of acceleration, contact number, and average force for roller speeds of 100–300 rpm. Based on similar behavior observed from photographic images of the experiments, the collision of garlic can be simulated in EDEM. The simulated accelerations were 2.8–7.8 times larger than the measured accelerations, which is attributed to an experimental limitation. The difference was reduced to 1.18 times after applying this limitation to the simulated data. In the simulations, the number of collisions decreased from 185 to 93 as the rotational speed increased, but the average force increased from 3.188 to 6.222 N. EDEM is suitable for simulating the collision of garlic with harvester conveying rollers. Therefore, EDEM can be applied to evaluate the impact forces acting on the garlic and to improve the structure of garlic harvesters.

Application of tuned liquid column ball damper (TLCBD) for improved vibration control performance of multi-storey structure.

Tuned liquid column ball damper (TLCBD) is a passive control device used for controlling the building vibrations induced from wind or earthquakes. TLCBD is a modified form of conventional tuned liquid column damper (TLCD). This paper studies the effect of TLCBD on the four-storey steel frame structure. The performance of the TLCBD is also compared with conventional TLCD. The analytical model of both TLCD and TLCBD is presented here. The effectiveness of these analytical models is examined experimentally by series of shaking table tests under different excitation levels including harmonic loadings and seismic excitations. In TLCBD, the vibration is reduced significantly as compared to TLCD by using steel ball as a moving orifice. The difference in diameter of steel ball and tube, containing the liquid column, acts as an orifice which moves with the movement of the ball. This moving orifice phenomenon enhanced the vibration reduction effect by resisting the water motion in the TLCBD. Root mean square (RMS) and peak values of acceleration were calculated for each loading and each storey of uncontrolled and controlled structures. Comparison of the time histories of controlled and uncontrolled structures for different loadings is also reported. Results indicate that the TLCBD is more effective in the earthquake scenarios as compared to the harmonic excitations. The TLCBD controls the vibration of the primary structure significantly in vibration reduction.

Transversal vibration analysis of the upper span of nonlinear closed-loop track systems

In order to analyze the effect of track pre-tension on the transversal vibration of the upper track, a multibody dynamics model of a tracked vehicle needs to be established. In view of the complex structure of tracked vehicles, the computational efficiency of conventional methods cannot meet engineering design requirements. In this paper, the Riccati Transfer Matrix Method for nonlinear closed-loop multibody systems is proposed and applied to the modeling and simulation of tracked vehicle systems. It avoids the overall dynamic equations of the system and achieves efficient computation with a smaller matrix scale. By selecting accelerations and forces as elements of the state vectors instead of coordinates and forces, linearization is avoided. The track chain is cut in a revolute joint. Its effect on the closed-loop system is represented by a set of constraint equations and internal constraint forces. An improved Riccati transformation for closed-loop systems is proposed to connect the internal force and acceleration parts in the state vector with the system constraint internal forces. The track pre-tension can be adjusted by moving the position of the idler relative to the chassis. The root mean square of vertical acceleration of mid-span with respect to the chassis is selected to evaluate the transversal vibration of the upper track. Simulation of a tracked vehicle driving on different road conditions is carried out with different idler displacements. Finally, a reasonable adjustment strategy for the track tensioner is proposed corresponding to different running conditions.

Usefulness root mean square (RMS) analysis using wearable sensors for assessing balance in neurodegenerative disorders

Postural instability is a common cause of sudden falls and fall-related injuries in patients with neurodegenerative diseases. Recently, using wearable sensors for assessing balance become alternative method for giving us objective and sensitive values. This study applied to 18 patients with sporadic adult-onset cerebellar ataxia (SAOA), 15 patients with Parkinson’s disease (PD), and 9 healthy controls. All participants were instructed to maintain an upright standing position in front of white wall, with performing visual conditions (eyes-open/close) and foot conditions (foot-open/close). To measure postural stability, we used a tri-axial gyro-based motion sensors attached to participant’s upper body. The mean distance reflecting the magnitude of AP (x) and ML (y) sway was analyzed by repeated measures ANOVA. Comparing with healthy control, patients with SAOA showed a larger mean distance. In Root Mean Square of Velocity (RMS) analysis, there was also a significant difference between 3 groups. As a result of Post-Hoc test, there was a significant difference between SAOA and PD group, and between SAOA and control group, however, there was no difference between PD and control group. In RMS acceleration analysis, three groups showed statistically significant differences. In detail, there were significant differences between SAOA and PD group, SAOA and control groups, but not between PD and control group. RMS and RMS acceleration showed disease specific characteristics. Our study shows not only usefulness as assessment tool but also evidence that has disease specific postural control system in neurodegenerative disease.

Numerical study on the influence of suspension damping on the bogie vertical vibration

The paper presents a study on the influence of suspension damping (SD) on bogie vertical vibrations generated by vertical track irregularities. The study is based on the results of the numerical simulations developed on the basis of a linear model with seven-degree of freedom of the bogie-track system, that takes into account the rigid vertical vibration modes of the bogie – bounce and pitch, vertical displacements of the wheels and rails, and the wheel-rail contact elasticity. The bogie vibration behaviour is assessed based on the dynamic response of the bogie chassis, expressed as the power spectral density of the vertical acceleration (PSD acceleration) at three reference points – at the bogie chassis centre and over the axles, and root mean square of vertical acceleration (RMS acceleration). It is highlighted the main characteristics of the bogie vibration behaviour according to the SD in correlation with the speed and quality of the railway track.

A study on the selection of ground motion measures for seismic capacity assessments of urban building complexes in Weinan

Selecting reasonable ground motion intensity measures (GMIMs) can facilitate more accurate seismic capacity assessments of urban building complexes (UBCs). In this study, basic structural classes (BSCs) were proposed to be used as analysis models for selecting GMIMs for UBCs in Weinan, China. A total of 171 BSCs for typical buildings were established under certain assumptions. In addition, 41 GMIMs were extracted from each of 273 ground motion records selected for analysis in this study and used to build a set of candidate optimal GMIMs. Moreover, each BSC was subjected to an elastic–plastic time-history analysis to determine its maximum inter-story drift ratio (MIDR). Furthermore, the corresponding relationships between the GMIMs and the MIDR of each BSC were established. The applicability of each GMIM for UBCs was evaluated using four metrics, i.e., correlation coefficient, effectiveness, practicability and sufficiency. Four GMIMs, namely, peak ground acceleration (PGA), root mean square of acceleration (aRMS), average spectral acceleration (Saavg) and velocity response intensity (VSI), were selected as optimal input GMIMs for seismic capacity assessment of UBCs in Weinan. This study provides a reference for selecting GMIMs for seismic capacity assessment of UBCs in Weinan.