Root Mean Square Acceleration Research Articles

Acoustic accelerometry reveals diel activity patterns in premigratory Port Jackson sharks.

Distinguishing the factors that influence activity within a species advances understanding of their behavior and ecology. Continuous observation in the marine environment is not feasible but biotelemetry devices provide an opportunity for detailed analysis of movements and activity patterns. This study investigated the detail that calibration of accelerometers measuring root mean square (RMS) acceleration with video footage can add to understanding the activity patterns of male and female Port Jackson sharks (Heterodontus portusjacksoni) in a captive environment. Linear regression was used to relate RMS acceleration output to time‐matched behavior captured on video to quantify diel activity patterns. To validate captive data, diel patterns from captive sharks were compared with diel movement data from free‐ranging sharks using passive acoustic tracking. The RMS acceleration data showed captive sharks exhibited nocturnal diel patterns peaking during the late evening before midnight and decreasing before sunrise. Correlation analysis revealed that captive animals displayed similar activity patterns to free‐ranging sharks. The timing of wild shark departures for migration in the late breeding season corresponded with elevated diel activity at night within the captive individuals, suggesting a form of migratory restlessness in captivity. By directly relating RMS acceleration output to activity level, we show that sex, time of day, and sex‐specific seasonal behavior all influenced activity levels. This study contributes to a growing body of evidence that RMS acceleration data are a promising method to determine activity patterns of cryptic marine animals and can provide more detailed information when validated in captivity.

Finite Element Model Updating and Verification of Satellite-borne Slot Waveguide Based on Random Vibration Test

For an axial free-floating slot waveguide, finite element model updating and verification based on the vibration data are studied. The slot waveguide and the free-floating side are modeled by shell element and spring element respectively. The two slot waveguide structures are applied to modal and random vibration test getting the modal frequencies, root mean square of acceleration. The finite element are first verified by tested modal data, and then the connecting stiffness will be updated by random vibration test data. These results show that the analytical dynamic responses of the updated finite element are well compared with the test responses, and the maximum error is 3.8%. The spring element could also model the free-floating side well and verify the accuracy for dynamic analysis.

Whole-body vibration and vertical road profile displacement power spectral density

ABSTRACT This study presents original new results on measured whole-body vibration (WBV) on passenger’s seat surface and seat base as a function of measured road unevenness in the longitudinal direction. Measurements were provided on nine different cars of six categories operated on about 1860 km of road network. Root mean square (RMS) of the frequency-weighted acceleration was used to quantify the WBV. The relation between passenger’s total vibration and road profile vertical displacement power spectral density (PSD) parameters (unevenness index, waviness) specified in standard ISO 8608: 2016 in a 200-m segment were estimated. Relation between ISO 2631-1 degrees of discomfort and ISO 8608 road classes was estimated. Measured acceleration at the passenger’s seat surface and seat base was fitted by a four-parameter function of unevenness index, waviness and vehicle speed. Further considered factors were vehicle type, road category, acceleration measuring point and direction of acceleration response.

Differences in gait and trunk movement between patients after ankle fracture and healthy subjects

BackgroundStudies have shown that gait asymmetry and activity limitation can persist several months or years after ankle fracture. However, evidence of gait and trunk movement patterns following ankle fracture during the early rehabilitation period is scarce. Thus, we compared gait patterns and trunk movement during the early phase of rehabilitation between patients with ankle fracture and matched controls.MethodsTen patients with ankle fractures, and ten age- and sex-matched healthy controls were prospectively enrolled. An automated infrared-assisted, trunk accelerometer-based gait analysis system was used to measure walking speed, step length, and cadence. The median time of the evaluation following ankle fracture was 4.0 months. Trunk movement intensity was evaluated as acceleration root mean square. Trunk movement symmetry and regularity were analysed using the autocorrelation method. Differences in gait characteristics between the patient and control groups were analysed using the Mann–Whitney U test. Follow-up assessment of falls was performed 24 months after the fracture. The correlations between Lower Extremity Functional Scale (LEFS) scores/falls and gait parameters were evaluated using Spearman’s rank correlation coefficient.ResultsWalking speed (p = 0.019), step length (p = 0.023), cadence (p = 0.003), and trunk movement intensity in anterior–posterior and vertical axis (p = 0.001, p = 0.003, respectively) were all significantly lower in the ankle fracture group than in the control group. Trunk movement symmetry in vertical direction (p = 0.019) decreased significantly in patients with ankle fractures, whereas between-strides regularity did not differ between groups. LEFS scores were moderately correlated with walking speed (r = 0.60, p = 0.044) and step length (r = 0.68, p = 0.021). During the 24 months after the fracture, 3 falls were reported by 3 patients. Trunk acceleration root mean square ratio in mediolateral axis (r = 0.72, p = 0.018) was highly correlated with future falls.ConclusionDuring early rehabilitation, patients with ankle fracture may develop trunk movement asymmetry in the vertical direction accompanied with slower walking speed and cadence, and smaller step lengths, which can contribute to muscular imbalances and potential injury. Thus, proper rehabilitation strategies should be employed for these patients.

Passsenger Ride Comfort and International Roughness Index Specifications in the Slovak Republic

New original results are presented on relation between passenger’s whole-body vibration (WBV) and longitudinal road unevenness characterised by the International Roughness Index (IRI) in 100-m segments. Measurements were provided in nine different cars of six vehicle categories operated on about 1860 km of road network. Vibration total value based on the root mean square (RMS) of the frequency-weighted acceleration was used to quantify the ride comfort at seat surface and seat base (i.e. vehicle floor) in three orthogonal axes. The relations between passenger’s acceleration response, comfort reaction levels according to the ISO 2631-1: 1997 and the IRI road unevenness classes, used by the Slovak Road Administration, were estimated. Results indicated higher WBV by ~ 20 % on the motorways than on the 1st and 2nd class roads in the same IRI road class. Using the same IRI road classes for motorways and the 1st and 2nd class roads seems not to be appropriate from the point of view of the whole-body vibrations.

On the longitudinal vibration of the railway bogie

This paper examines the influence of the rebound longitudinal motion of the bogie upon the vibration behaviour in the bogie. The analysis is based on the results of the numerical simulations developed on the basis of a general model with a nine-degree freedom of the bogie-track system, which takes into account the rigid vibration modes of the bogie – bounce, pitch and rebound, vertical and longitudinal displacements of the wheels, vertical displacements of the rails, and the wheel-rail contact elasticity, and a simplified model that does not consider the bogie longitudinal vibrations of rebound. The bogie vibration behaviour is assessed based on the power spectral density of the vertical acceleration and root mean square of vertical acceleration. It is highlighted the increase of the vibration level of the bogie due to the coupling effect between the pitch and rebound longitudinal vibrations, which, however, does not exceed 3-4% in terms of acceleration.

Experimental Verification of Method to Synthesize the Track Vertical Irregularities

Abstract The paper focuses on the experimental verification of the results derived from numerical simulations, based on a model of the bogie-track system, where the vertical track irregularities are introduced in the form of a pseudorandom function. This function comes from an original method of synthesizing the vertical track irregularities, depending on the geometric quality of the track and on the velocity. To verify the method, the root mean square (RMS) of the simulated accelerations in the axles and the bogie frame against each axle is compared to the experimental accelerations within the frequency range of wavelengths of the track vertical irregularities from 3 to 120 m. The results have shown a good correlation between the simulated RMS accelerations for a low quality track and the measured RMS accelerations.

Effect of Frequently Using Workshop Tools on Worker's Hand Arm Vibration and Safety

In the workshops of agricultural sector there are a lot of technical jobs which widely use hand-held or bench-top workshop power tools such as angle grinders, drills, riveters, chain saw, pneumatic hammers and torque wrenches. Which consider the most important sources of hand arm vibration (HAV) These workshop power tools are known to transmit substantial vibrations to the operators/worker's hand and arm and act as vibrations resource consequently, create problems for operators/workers who regularly exposure to hand arm vibrations. Therefore, the main objective of this investigation is to study the effect of frequently using of workshop tools on worker's hand arm vibration and safety. The study selected eight representatives healthy workers were well familiar with the workshop power tools control levers and had sufficient experience of operating some power tools from both bench-top and hand held workshop power tools (stand drill, wheel grinder, disc cutter, angle grinder impact drill, and rotary hammer drill with different spare discs under two different working postures as vertically erected and squeeze) during five different operations, namely, grinding, drilling, cutting, breaking and polishing using three types of materials (metal, wood and concrete). Parameters such as frequency-weighted vibration acceleration in root mean square (RMS), heart pulses rate (HR), blood pressure (BP), work related body pain (WRBP), stand height, arm length and mass of operators were evaluated. Vibration measurements were performed according to (ISO 5349-2: 2001). Workshops operations were conducted in a statistically designed layout (randomized complete blocks design) and were conducted at applied research farm of Rice Mechanization Center, Meet Eldeeba, Kafr El-Sheikh Governorate, in the 2018. The obtained results indicated that the cutting by the angle grinder gives the highest HAV data of the frequency weighted RMS acceleration magnitude while, the largest single orthogonal axis is in the axis (X) which exceeded than both of exposure action value and exposure limit value. This causes a high risk on the worker hand-arm which increases the heart rate and blood pressure followed by the polishing by the hand angle grinder. On the other hand, the HAV emission level recorded the lowest values during grinding by the bench-top wheel grinder and drilling by the bench-top stand drill consequently; there is no risk on the operator hand-arm and also the heart rate and blood pressure. Using rubber gloves during cutting by the hand angle grinder leads to a decrement percentages in the HAV values and so heart rate and blood pressure. The maximum WRBP values were obtained during the cutting by the angle grinder on working squeeze posture followed by cutting by the angle grinder on working normal posture and polishing by the angle grinder. Maximum pain levels of 15.6, 14.8 and 13.6 (Borg scale) were observed respectively. Results showed that there are significant differences between RMS, SBP, DSBP and heart rate during the different workshop operations.

Acute and Delayed Neuromuscular Alterations Induced by Downhill Running in Trained Trail Runners: Beneficial Effects of High-Pressure Compression Garments.

Introduction: The aim of this study was to examine, from a crossover experimental design, whether wearing high-pressure compression garments (CGs) during downhill treadmill running affects soft-tissue vibrations, acute and delayed responses in running economy (RE), neuromuscular function, countermovement jump, and perceived muscle soreness.Methods: Thirteen male trail runners habituated to regular eccentric training performed two separate 40-min downhill running (DHR, –8.5°) sessions while wearing either CGs (15–20 mmHg for quadriceps and calves) or control garments (CON) at a velocity associated with ∼55% of VO2max, with a set of measurements before (Pre-), after (Post-DHR), and 1 day after (Post-1D). No CGs was used within the recovery phase. Perceived muscle soreness, countermovement jump, and neuromuscular function (central and peripheral components) of knee extensors (KE) and plantar flexors (PF) were assessed. Cardiorespiratory responses (e.g., heart rate, ventilation) and RE, as well as soft-tissue vibrations (root mean square of the resultant acceleration, RMS Ar) for vastus lateralis and gastrocnemius medialis were evaluated during DHR and in Post-1D.Results: During DHR, mean values in RMS Ar significantly increased over time for the vastus lateralis only for the CON condition (+11.6%). RE and cardiorespiratory responses significantly increased (i.e., alteration) over time in both conditions. Post, small to very large central and peripheral alterations were found for KE and PF in both conditions. However, the deficit in voluntary activation (VA) was significantly lower for KE following CGs (–2.4%), compared to CON (–7.9%) conditions. No significant differences in perceived muscle soreness and countermovement jump were observed between conditions whatever the time period. Additionally, in Post-1D, the CGs condition showed reductions in neuromuscular peripheral alterations only for KE (from –4.4 to –7.7%) and perceived muscle soreness scores (–8.3%). No significant differences in cardiorespiratory and RE responses as well as countermovement jump were identified between conditions in Post-1D.Discussion: Wearing high-pressure CGs (notably on KE) during DHR was associated with beneficial effects on soft-tissue vibrations, acute and delayed neuromuscular function, and perceived muscle soreness. The use of CGs during DHR might contribute to the enhanced muscle recovery by exerting an exercise-induced “mechanical protective effect.”

Optimization of hydropneumatic suspension for articulated wheel loader based on kriging model and particle swarm algorithm

Articulated wheel loaders that travel on unstructured roads experience severe vibration and poor stability. Introducing suspended axles on wheel loaders, which are traditionally constructed without wheel suspension, is desirable for ride comfort. This study mainly focuses on the parameter optimization of the hydropneumatic suspension to obtain the minimum root mean square of vertical accelerations under different driving conditions, thereby improving the ride comfort of the wheel loader. The multibody model of the wheel loader with hydropneumatic suspension was developed by RecurDyn in co-simulation with MATLAB/Simulink. The vertical acceleration root mean square at the seat position was analyzed when the wheel loader was traveling on class C, D, and E roads with different travel speeds. The surrogate model of the vertical acceleration root mean square with respect to the suspension parameters was established based on kriging method. The established surrogate model was then optimized using particle swarm optimization algorithm. The optimization results of the hydropneumatic suspension parameters of the wheel loader under different road excitations and driving speeds were obtained. Simulation and optimization results show that a well-designed hydropneumatic suspension system can significantly improve wheel loader performance in reducing the vertical acceleration at the seat position compared to a suspension system without optimization.

Multi-objective optimization for ride comfort of hydro-pneumatic suspension vehicles with mechanical elastic wheel

The new mechanical elastic wheel has the following advantages: non-pneumatic, anti-puncture, and explosion-proof. However, the larger radial stiffness is detrimental to vehicle ride comfort. To solve this problem, an integrated design method of hydro-pneumatic suspension matching mechanical elastic wheel is proposed in this paper. First, the nonlinear radial stiffness of mechanical elastic wheel is fitted by static loading experiment. Next, the mathematical model of hydro-pneumatic suspension is derived. Then, a half-car model, integrating hydro-pneumatic suspension and mechanical elastic wheel, is established. Finally, the top two optimization objectives, including vertical centroid acceleration root mean square and pitch acceleration root mean square, are optimized simultaneously, based on the Pareto multi-objective artificial fish swarm algorithm. The obtained results show that the optimization effect of multi-objective artificial fish swarm algorithm is obvious; the two optimization objectives have been optimized significantly. The proposed method that hydro-pneumatic suspension integrated with mechanical elastic wheel gains critical reference value for the design and optimization of vehicle chassis in theory and practice.

Modeling and analytic optimization of dynamic comfort for wheelchair robots undergoing random roads

To make a rapid comfort assessment and a reasonable dynamic parameters choice of wheelchair robots, this paper proposes a dynamic comfort coefficient [Formula: see text] and analytically optimizes the cushion damping. Firstly, a traveling vibration model of the occupant-wheelchair system for wheelchair robots running on random roads was created. Secondly, the analytic formula of the occupant RMS (root mean square) acceleration was deduced. Moreover, the dynamic coefficient [Formula: see text] was proposed and its influence laws were revealed. Finally, the cushion system optimal damping ratio was calculated based on [Formula: see text]. The results show that the [Formula: see text] value is only determined by the parameters of the occupant-wheelchair system. The smaller the [Formula: see text] value is, the better the dynamic comfort is for wheelchair robots running on random roads. By minimizing [Formula: see text], the occupant-wheelchair system can achieve a statistically optimal dynamic comfort effect.

Upper body accelerations during level walking in transtibial amputees.

The observation of upper body movement is gaining interest in the gait analysis community. Recent studies involved the use of body-worn motion sensors, allowing translation of laboratory measurements to real-life settings in the context of patient monitoring and fall prevention. It was shown that amputee persons demonstrate altered acceleration patterns due to the presence of prosthetic components, while no information is available on how accelerations propagate upwards to the head during level walking. This descriptive study aims to fill this gap. Original research report. Twenty definitive prosthesis users with transtibial amputation and 20 age-matched able-bodied individuals participated in the study. Three magneto-inertial measurement units were placed at head, sternum and pelvis level to assess acceleration root mean square. Three repetitions of the 10-m walking test were performed at a self-selected speed. Acceleration root mean square was significantly larger at pelvis and head level in individuals with amputation than in able-bodied participants, mainly in the transverse plane ( p < 0.05). Differences were also observed in how accelerations propagate upwards, highlighting that a different motor strategy is adopted in amputee persons gait to compensate for increased instability. The obtained parameters allow an objective mobility assessment of amputee persons that can integrate with the traditional clinical approach. Transtibial amputees exhibit asymmetries due to the sound limb's support prevalence during gait: this is evidenced by amplified accelerations on the transverse plane and by related differences in upper body movement control. Assessing these accelerations and their attenuations upwards may be helpful to understand amputee's motor strategies and to improve prosthetic training.

Influence of the interference of bounce and pitch vibrations upon the dynamic behaviour in the bogie of a railway vehicle

The dynamic behaviour of the bogie of the railway vehicle is generally studied by capitalizing on the advantage of the symmetrical construction, which allows the vibrations in the vertical be considered decoupled from the ones in the horizontal plan. Likewise, the bounce and pitch vertical vibrations of the bogie are decoupled, due to the fact that elastic and damping elements with identical characteristics are normally used in the suspension corresponding to each axle of the bogie. The paper studies a particular situation, correlative with the failure of a damper in the primary suspension of a two-axle bogie. As a consequence of the damping reduction, an imbalance in the system occurs that will prompt dynamic interferences between the bounce and pitch vibrations of the bogie. The level of vibrations will rise, a fact focused on in the paper as based on the results from the numerical simulations, which represent the frequency response functions of the bogie calculated in the three reference points of the bogie, for different cases of reduction in the damping constant, compared with the reference value. The increase of the level of vibrations has an impact on the dynamic behaviour of the bogie, evaluated on the basis of the root mean square of the vertical acceleration.

Multi-objective optimization modification of a tooth surface with minimum of flash temperature and vibration acceleration RMS

The minimum of tooth surface flash temperature and vibration acceleration RMS design is proposed and analyzed. The tooth contact analysis (TCA) and the load tooth contact analysis (LTCA) method and multi-objective optimization are also detailed. Satisfying design variables in multiple physical quantities leads to the minimum of multi-objective optimization. Considering the tooth surface loading conditions are uniform or not, the optimal modification of the tooth surface for improving gear comprehensive characteristics under various load bearing conditions is improved. The tooth surface flash temperature and vibration acceleration root mean square (RMS) values in different transmission modes of marine ship power rear gears drive system are derived. This research considers the multi-objective optimization modifications of tooth surface, and its main purpose is to propose an approach to help design tooth corrections to simultaneously optimize several objective physical quantities.

Gait alterations on irregular surface in people with Parkinson's disease

BackgroundPersons with Parkinson's disease are at high risk for fall-related injuries with a large proportion of falls occurring while walking, especially when the walking environments are complex. The aim of this study was to characterize gait parameters on irregular surface for persons with Parkinson's disease. MethodsThree-dimensional gait analysis was conducted for nine persons with Parkinson's disease and nine healthy age-matched adults on both regular and irregular surfaces. Repeated ANOVA and paired t-test were performed to determine the effect of surface and group for spatiotemporal, kinematic and stability variables. FindingsIndividuals with Parkinson's disease showed a larger ratio of reduction for speed, cadence and step length than controls when the surface changed from regular to irregular. The ankle transverse range of motion and root mean square of trunk acceleration increased on irregular surface for both groups. Additionally, individuals with Parkinson's disease demonstrated a decreased knee sagittal range of motion and trunk frontal and transverse range of motion compared with controls, especially on the irregular surface. InterpretationThe irregular surface posed a greater challenge to maintain balance and stability for individuals with Parkinson's disease. A relatively small knee range of motion in the sagittal plane and large root mean square of trunk acceleration increased the potential fall risk for individuals with Parkinson's disease. This information improves the understanding of parkinsonian gait adaptations on irregular surfaces and may guide gait training and rehabilitation interventions for this high fall-risk population.

Acceleration profile of an acrobatic act during training and shows using wearable technology

The purpose of this study was to describe the mechanical characteristics of a trampoline circus act and its individual tracks performed in training and shows using a tri-axial accelerometer. A track is an artist’s specific role within a choreographed act. Seven male acrobats performed their trampoline act during training and shows while wearing a triaxial accelerometer and reported ratings of perceived exertion (RPE) after each trial. Average acceleration (AVG), root mean square (RMS), root mean to the fourth (RM4), time spent in specific acceleration ranges and RPE were measured/recorded from training and show acts. Paired t-tests compared dependent variables between training and show. Acceleration AVG, RMS and RM4 were significantly higher (p < 0.05) in training than show. RPE was significantly higher (p < 0.05) in show than training. No significant differences existed in time spent in any of the acceleration ranges between training and show. GPS devices have been used to manage workloads in field sports but are inoperable in theatres. But, inertial measurements may be an effective alternative to describe mechanical demands in theatre or arena environments. Wearable technology may be useful to coaches to improve understanding of track demands to manage artist workloads.

Centre of Mass Acceleration-Derived Variables Detects Differences between Runners of Different Abilities and Fatigue-Related Changes during a Long Distance Over ground Run

Background: Wireless accelerometers provide a method of performing running assessments in sports-specific environments. The purpose of this study was to investigate differences in running movement using centre of mass acceleration-derived variables between runners of varying skill levels and examine fatigue-related changes during a long distance over ground run. Methods: Ninety-two runners performed a self-selected paced long distance over ground run, with a tri-axial accelerometer attached to their low back. Runners were divided into four groups (elite, advanced, intermediate and slow) based on their finishing run time. Spatiotemporal (contact time, flight time, step frequency), dynamic postural stability (ratio of root mean square of accelerations), dynamic loading (peak impact and braking accelerations) and variability (step and stride regularity), were derived from acceleration data. Speed and acceleration-derived variables were used to investigate between group differences and within group fatigue-related changes. Results: Faster runners (elite and advanced groups) exhibited significantly shorter contact times and higher step frequencies than the slow group. Fatigue-related changes throughout the run were only observed amongst the slower runners (intermediate and slow groups). The main changes in the intermediate group were an increase in ratio of root mean square in mediolateral acceleration, and a decrease in speed in the slow group. Conclusion: The shorter contact times and higher step frequencies and no fatigue-related changes exhibited by the faster runners indicate an efficient running movement pattern. Fatigue-related changes in the slower runners were a decrease in postural dynamic stability in mediolateral direction in the intermediate group and a decrease in speed in the slow group which impacted on performance. These runners would benefit from exercise interventions and pacing strategies to reduce these fatigue-related changes and improve performance.

Investigation on vibration scuffing life curves

The printing images on products and packaging play an important role in increasing the business value, adding artistic quality, and sending information. During transportation, scuffing of the printing images will emerge due to vibrations and impacts induced by rough roads and vehicles. This paper investigates experimentally the vibration scuffing through an ink transfer device. The scuffing value–time curves are obtained. Then the scuffing life curves Grms,e‐Na,e based on excitation acceleration root‐mean‐square (RMS) and Grms,r‐Na,r based on relative acceleration RMS are developed. Both Basquin‐type and exponential‐type curves may be applied to describe the scuffing life in this case. The excitation frequency width covering the resonance frequency has a significant effect on the scuffing life curve Grms,e‐Na,e based on excitation acceleration RMS; however, it is not obvious on the scuffing life curve Grms,r‐Na,r based on relative acceleration RMS. The vibration system filters out the broadband excitation vibration frequencies away from the resonance zone and makes the relative acceleration signal a narrow one. The scuffing life curve in the resonance scuffing state is very different from that in the nonresonance scuffing state, and they should be distinguished in practical application. The scuffing life equations and curves obtained in this paper may provide a reference to the further research on packaging scuffing and its test evaluation and accelerated vibration test in laboratory.

Multi-objective optimization of tooth surface based on minimum of flash temperature and vibration acceleration root mean square

Marine ship gears are increasingly subject to strict requirements in terms of tooth surface load capacity, dynamic performance, vibration and noise generation, and so on. The optimization of tooth ...