Input Acceleration Research Articles

Dynamic response and vibration isolation of pipes inside a utility tunnel passing through nonhomogeneous soil under seismic action

An unreasonable design of the pipe support between a utility tunnel and the pipe can result in a large deformation of internal pipes under seismic action. In this study, aiming at the seismic response problem of pipes inside a utility tunnel passing through nonhomogeneous soil, a shaking table test and a finite element simulation were conducted. First, the boundary effect caused by the laminated shear box was studied, and the influences of the pipe acceleration, longitudinal and transverse relative slippages, the form of the pipe support, and the pipe material on the pipe deformation were analyzed. Finally, the attenuation effect of the acceleration peak response of the internal pipes and the attenuation law of the energy transmitted to the pipes were obtained. The results showed that the attenuation degree of the energy transmitted to the pipes was more than 80%; the longitudinal relative slippage of the pipes caused by the high-amplitude segment of the input acceleration was generally significant; the vibration isolation effect of the side-wall angle steel support on the pipeline was stronger than those of other supports. This paper provides a basis for the seismic design of pipelines inside a utility tunnel.

Concurrent Validity and Reliability of Sprinting Force-Velocity Profile Assessed With GPS Devices in Elite Athletes.

The aims of this study were to (1) assess the concurrent validity of global positioning systems (GPSs) against a radar device to measure sprinting force-velocity (F-v) profiles and (2) evaluate the interunit reliability of 10-Hz GPS devices (Vector S7, Catapult Innovations). Sixteen male elite U18 rugby union players (178.3 [7.6]cm; 78.3 [13.2]kg) participated. Two 50-m sprints interspersed with at least 5minutes of recovery were completed to obtain input (maximal sprint speed and acceleration time constant τ) and output (theoretical maximal horizontal force, sprinting speed, and horizontal power) F-v profile variables. Sprint running speed was concurrently measured with a radar and 2 GPS units placed on the upper back of each player. Concurrent validity and interunit reliability analyses were performed. Moderate to nearly perfect correlations were observed between radar and GPS-derived F-v variables, with small to large typical errors. Trivial to small coefficients of variation were found regarding the GPS interunit reliability. The GPS devices tested in this study represent a valid and reliable alternative to a radar device when assessing sprint acceleration F-v profiles in team-sport players.

Design, modeling, and frequency domain analysis with parametric variation for fixed-guided vibrational piezoelectric energy harvesters

The aim of the presented work is to design, model, and analyze the fixed-guided two-beam (FG2B) & fixed-guided four-beam (FG4B) piezoelectric energy harvesters, especially for ambient mechanical energy harvesting applications. Two and four rectangular beams are connected at the middle of the square-shaped seismic-mass in these configurations. The performance of the energy harvesters is analyzed using eigen-mode analysis and frequency domain analysis. To determine the resonance frequency of the energy harvesters the eigen-mode analysis is performed. The frequency domain analysis is coupled with parametric sweep analysis to analyze the effect of variation in input acceleration from 1g to 5g (g=9.8m/s2) on von Mises stress, displacement, electric potential, and output electric power. The main aim of the energy harvester is to generate electric power from the ambient mechanical vibrations. The reported FG2B and FG4B energy harvester produce an optimum electric output power of 0.55µW and 0.25µW at the maximum load resistance of 0.52MΩ and 0.2MΩ, respectively, with the electric potential of 0.8V and 0.32V respectively. Hence, the proposed energy harvesters generate higher electric potential and output power at a higher resistive load range with less device volume than the work reported in the literature. The designed energy harvesters resonate at around 550 Hz and 770 Hz for FG2B and FG4B respectively, which is in the low-frequency range and hence can be efficiently utilized for low-frequency energy harvesting applications with better electrical output power.

Experimentally investigating the effect of viscoelastic joint of a cantilever beam containing piezoelectric patch on the harvested energy

The purpose of this study was to examine the effect of the connecting beam to the main structure considering the viscoelastic property, which affects the rate of electrical energy harvested from the piezoelectric patch connected to the aluminum beam. In this research, the connection of the beam to the vibrator was considered viscoelastic to obtain more accurate results. Viscoelastic material decreases the amount of stress and strain along the beam as well as the piezoelectric path due to its softness; thus, less potential difference is expected to be produced than the rigid connection. First, the beam is deformed by a base harmonic excitation on the beam containing the piezoelectric path, which generates an electric potential difference on both sides of the piezoelectric. In this study, the behavior of an aluminum beam with a piezoelectric patch and viscoelastic connection under loading and excitation of the harmonic base is examined based on experimental testing and 3D finite analysis. The experiment was performed by connecting an aluminum beam to a vibrator rotating unbalance system to create a harmonic base excitation under the connection of viscoelastic adhesive and rigid connection of bolts and nuts. The finite element method was used for numerical solution by Ansys software. The piezoelectric patch used in this analysis was of 5A type with two piezoelectric layers and a brass layer. Viscoelastic simulation was modeled in the 3D form using a special viscoelastic element in an Ansys environment. In order to solve the harmonic problem, the loading was considered as the base excitation with input acceleration. The diagrams of the electric potential difference revealed that the amount of energy harvested from the viscoelastic joint was less than that from the rigid joint. In addition, modeling of the viscoelastic joint by the Kelvin–Voigt and the Maxwell mechanical model shows that the results of these two joint models are more consistent with the result obtained by the standard solid joint. Electrical power diagrams were drawn considering different resistances. It is obvious that the amount of harvested power increased with increasing input frequency. Finally, the results of 3D finite element analysis were compared to the results of energy harvesting experimentally for verification.

System Identification For Enhanced Flow Description From Multi-Pulse PIV

We propose a novel approach to obtain a time-resolved description from non-time-resolved PIV measurements. The method needs in input velocity and acceleration fields from ( at least) 3-pulse PIV data, without time r esolution. A sparse identification of nonlinear dynamics (based on the SINDy technique) is carried out to estimate the time history of coordinates in a low-dimensional space from Proper Orthogonal Decomposition (POD). The output is a reduced-order model of the dynamics which can be integrated to obtain time-resolved velocity fields using t he s napshots as i nitial c onditions. The t ime-resolved e volution of t he pressure fields is th en derived from the momentum equation. The time history of the velocity and pressure fields is obtained through a weighted Backward-Forward Integration (BFI) of the identified s ystem. Time super-sampling can be achieved by integration between consecutive non-time-resolved realizations. In alternative, simple one-directional time integration can be used for short-time prediction starting from individual snapshots. The algorithm is validated using a synthetic test case from 2D Direct Numerical Simulation of the wake of a fluidic pinball at a Reynolds number Re equal to 130, and PIV measurements of the wake of a NACA 0018 wing profile with Re = 4 800. We show that the method is able to reconstruct the flow dynamics for horizons of several convective times, provided that the basis for the data reduction is sufficiently c ompact. Our results suggest that manifold learning and data assimilation can be combined to obtain an enhanced flow description.

Conducting polymer-based generators for vibro-electrochemomechanical energy conversion and harvesting

Energy harvesting technologies have received much attention to alleviate providing energy crisis by batteries for different applications including sensors and actuators. Compared to other sources, mechanical energy is more available and most widely distributed. Conducting polymers as piezoionic materials have gained a large number of attention in light of their advantages of having promising electrical and mechanical properties for electrochemical energy conversion and storage. In this paper, conducting polymer-based PEDOT/IPN/PEDOT trilayer structure is proposed for electrochemomechanical energy harvesting applications. For the proposed trilayer power generator, the vibro-electrochemomechanical model is demonstrated. In this modeling approach, the mechanical behavior of the trilayer is modeled in finite element software to capture the induced strain due to vibration input. Resistive-capacitive transmission line model is implemented to model the electrochemical response of the trilayer to mechanical input which is induced strain and predict the generated voltage. Finally, the simulation results show the ability of the energy harvester to convert the 2 g and 20 mm input acceleration and displacement to electrical energy and generate 986 µW power. This model enables one to find the best parameters and also calculate the potential generating power to have an optimal design.

Experimental Investigations of the Seismic Performance of a Base-Isolated Uninterruptible Power Supply (UPS) through Shaking Table Tests

Seismic performance of a UPS through shaking table tests was investigated using the input acceleration time histories with scaling factors of 50%, 100%, and 200%. The first series consists of UPS specimens supported by snip single-corner rectangular pins, and the second series consists of UPS specimens supported by isolator systems. The UPS specimens in the second series significantly reduced the fundamental frequency, peak acceleration, and amplification factors but increased the damping ratio and displacement compared with those of the UPS specimens in the first series. The analytical results obtained from the analytical model agreed well with the experimental results.

A Comparative Simulation Study of the Different Variations of PZT Piezoelectric Material by Using A MEMS Vibration Energy Harvester

In this article, the presented work aims to scavenge maximum electrical outputs by using the novel microelectromechanical system flared-U shaped spring based piezoelectric vibration energy harvester (PVEH). The performance studies were carried out by employing four different variations of lead zirconate titanate (PZT) piezoelectric material namely PZT-4, PZT-5A, PZT-5H, and PZT-8 in the same size and shape of the proposed device. The maximum output powers employing PZT-4, PZT-5A, PZT-5H, and PZT-8 piezoelectric materials are 7.156 nW, 8.657 nW, 10.738 nW, 5.701 nW over 30 Hz, 28.4 Hz, 28.6 Hz, and 30.2 Hz, resonant frequency, respectively, at input acceleration of 0.07 g. From the finite element method simulator COMSOL Multiphysics 5.4 (licensed version) simulation-based outcomes, it is inferred that PZT-5H piezoelectric material performs better than other variations of PZT, such as PZT-4, PZT-5A, and PZT-8 piezoelectric materials.

Control Scheme for Rapidly Responding Register Controller Using Response Acceleration Input in Industrial Roll-To-Roll Manufacturing Systems

A roll-to-roll (R2R) manufacturing system has been considered the most suitable candidate for commercializing flexible electronic devices owing to its large-area and mass-production characteristics. A high-precision register control should be ensured when fabricating devices using the R2R system. Contrary to conventional manufacturing systems that are applied to rigid materials, the control target in an R2R system is a flexible film that can lead to a substantial time delay in the control response and degrade the register control performance. This article proposes a novel control scheme, namely response acceleration input, to provide a rapid response in the register control of flexible substrates. Mathematical models to achieve the proposed scheme were developed. A register control system based on the developed models was designed, followed by experimental verifications using an industrial-scale R2R system. The results show that the register error is successively controlled below ±10 µm with a high yield of over 80% for 1800 s. We believe that the proposed control strategy can realize a high-precision register control below ±10 µm in industrial-scale R2R manufacturing systems, thus enabling the commercialization of multilayered, flexible electronic devices.

Envelope time reversal with a nonlinear time lens based on accelerating quasi-phase-matching

We show theoretically and numerically that a time-reversed replica of the pump pulse envelope in a frequency converted signal can be achieved using a nonlinear time lens realized with an accelerating spatiotemporal quasi-phase-matching (QPM) modulation. The nonlinear process depends on a suitable combination of the input and output dispersion and acceleration rate of a quadratic spatiotemporal QPM modulation.

Valve control of a hydraulically interconnected suspension system to improve vehicle handling qualities

This paper deals with the control of a hydraulically interconnected suspension system to improve the handling performance of the vehicle. A seven-degrees-of-freedom MATLAB/Simulink vehicle model and an Adams/Car model are used for simulation purposes. A Simscape model for analysing the hydraulic subsystem is also employed. It was observed that the yaw rate and roll responses of the vehicle are influenced to a large extent by the flow control valve opening values. The handling performance of the vehicle was investigated by the control of the orifice valves and their adjustment according to the lateral acceleration inputs. Considerable improvements were obtained in the handling qualities without sacrificing the ride responses, compared to the responses of a passive interconnected suspension.

Development and testing of braking and acceleration features for vehicle advanced driver assistance system

<span lang="EN-US">Traffic congestion is a constant problem for cities worldwide. The human driving inefficiency and poor urban planning and development contribute to traffic buildup and travel discomfort. An example of human inefficiency is the phantom traffic jam, which is caused by unnecessary braking, causing traffic to slow down, and eventually coming to a stop. In this study, a brake and acceleration feature (BAF) for the advanced driver assistance system (ADAS) is proposed to mitigate the effects of the phantom traffic phenomenon. In its initial stage, the BAF provides a heads-up display that gives information on how much braking and acceleration input is needed to maintain smooth driving conditions, i.e., without sudden acceleration or deceleration, while observing a safe distance from the vehicle in front. BAF employs a fuzzy logic controller that takes distance information from a light detection and ranging (LIDAR) sensor and the vehicle’s instantaneous speed from the engine control unit (ECU). It then calculates the corresponding percentage value of needed acceleration and braking in order to maintain travel objectives of smooth and safe-distance travel. Empirical results show that the system suggests acceleration and braking values slightly higher than the driver’s actual inputs and can achieve 90% accuracy overall.</span>

Comfort Assessment in Railway Vehicles by an Optimal Identification of Transfer Function

Purpose: This research proposes a multi-input multi-output (MIMO) model, based on a data-driven approach, to assess passenger vibration comfort on rail vehicles. The MIMO model represents the mathematical relationship between input and output variables that contains modal properties and vibration transmission. An optimization algorithm estimates the frequency response functions at the interface seat-passenger of the trains. Methods: The MIMO model evaluated the frequency response functions along x-, y- and z- axis. Multivariate analysis considered the calculation of the partial coherence functions, the cross-correlation functions, and the Anderson-Darling nonparametric test. Results: This research considered the acceleration measurements on two Trains, one Tramway, and one Underground. This research developed accelerations analyses in the time domain; the transmissibility of accelerations in the frequency domain. The measuring points were on the seat base and the interface seat-passenger of the trains. The frequency response data, obtained experimentally according to x- y- and z- axis, generated a multi-input and multi-output frequency response model. This research is based on experimental investigations and statistical tests. The calculation of partial coherence evaluated the percentage of spectrum output due to a specific (conditional) input. The partial coherences assess the energy contribution of each input to the output. The cross-correlation test showed the phase between input and output accelerations. The Anderson- Darling test showed the provenance of the data sample from a population with a specific distribution. Anderson-Darling's nonparametric test attaches weight to tails. Conclusions: The seats of the trains were exposed to complex vibrations according to the three directions x, y, and z. The three inputs are linear accelerations along the vertical, lateral, and forward direction of the seat base. If the accelerations on the seat base represented the inputs to the MIMO model, the accelerations acquired at the passenger-seat interface represented the output of the MIMO model.

LEAP-ASIA-2019: Validation of centrifuge experiments and the generalized scaling law on liquefaction-induced lateral spreading

A round-robin centrifuge model test for an identical saturated sloping deposit with various initial conditions was conducted in the framework of liquefaction experiments and analysis project (LEAP) with 10 international institutes. To pursue two main objectives: (1) the validation of the generalized scaling law (GSL); and, (2) the development of additional experimental data that fill the gaps in the previous LEAP, each institute was assigned two tests, identical in prototype scale: a model following the generalized scaling law and a model following conventional centrifuge scaling law. The test results show a significant match in the dynamic behavior of these models, which validates the applicability of the GSL under given conditions. However, in this study, a deviation is observed when the surface ground deformation becomes larger (i.e., 250 mm). The trend surface that correlates peak amplitude of input acceleration (PGAeff), the relative density of the ground (Dr_qc(2.0 m)), and surface lateral displacement (Ux) is updated and confirmed with new data sets.

Time history analysis for investigation of dynamic behavioral characteristics of uninterruptible power supply system

ABSTRACT This paper presents a seismic investigation of an uninterruptible power supply system (UPS) through triaxial shake table tests. A 100-kVA uninterruptible power supply system compliant with IEC-60950 was selected as the test specimen. The input acceleration time histories were generated based on the ICC-ES AC156 code, with scaling factors ranging from 25% to 600%. Based on the test results, the damage of the UPS and dynamic characteristics of this device were evaluated and explained in terms of fundamental frequency, damping ratio, acceleration time history response, dynamic amplification factor, and relative displacement. In addition, a simplified analytical model was proposed, and a parametric study was conducted to understand the dynamic characteristics of the UPS.

Numerical and experimental evaluation of the magnetic interaction for frequency up-conversion in piezoelectric vibration energy harvesters

The purpose of this work is to improve the modelling process for the application of permanent magnets in a frequency up-conversion (FuC) mechanism for piezoelectric energy harvesters. More specifically, the aim is to avoid the burdensome finite element analyses (FEA) in the framework of electromechanical devices design. The analytical calculations are compared with experimental tests conducted by an ad-hoc set up and with FEA. After investigations on the interaction, an application of FuC mechanism is proposed on a meso-scale case study in which a low frequency seismic mass (LFM) interacts non-linearly, due to magnetic field, with an high frequency piezoelectric vibration energy harvester (PVEH). Numerical simulations have been carried out in the time domain (step-by-step analysis) under a harmonic low-frequency input acceleration signal. The peculiar behavior, due to non-linear dynamics, is investigated in both the repulsive and the attractive configurations of the magnets. The results confirm the effectiveness of magnetic FuC and show that the repulsive case allows the device to recover a larger amount of energy than the attractive configuration.

Energy Expenditure Estimation of Tabata by Combining Acceleration and Heart Rate.

Tabata training plays an important role in health promotion. Effective monitoring of exercise energy expenditure is an important basis for exercisers to adjust their physical activities to achieve exercise goals. The input of acceleration combined with heart rate data and the application of machine learning algorithm are expected to improve the accuracy of EE prediction. This study is based on acceleration and heart rate to build linear regression and back propagate neural network prediction model of Tabata energy expenditure, and compare the accuracy of the two models. Participants (n = 45; Mean age: 21.04 ± 2.39 years) were randomly assigned to the modeling and validation data set in a 3:1 ratio. Each participant simultaneously wore four accelerometers (dominant hand, non-dominant hand, right hip, right ankle), a heart rate band and a metabolic measurement system to complete Tabata exercise test. After obtaining the test data, the correlation of the variables is calculated and passed to linear regression and back propagate neural network algorithms to predict energy expenditure during exercise and interval period. The validation group was entered into the model to obtain the predicted value and the prediction effect was tested. Bland-Alterman test showed two models fell within the consistency interval. The mean absolute percentage error of back propagate neural network was 12.6%, and linear regression was 14.7%. Using both acceleration and heart rate for estimation of Tabata energy expenditure is effective, and the prediction effect of back propagate neural network algorithm is better than linear regression, which is more suitable for Tabata energy expenditure monitoring.

An Engineered Multifunctional Composite for Passive Sensing, Power Harvesting, and In Situ Damage Identification with Enhanced Mechanical Performance

AbstractA multifunctional fiber‐reinforced composite with passive self‐sensing, energy‐harvesting, and damage detection capabilities is presented. Here, barium titanate piezoelectric microparticles are deposited on basalt fibers by a scalable, low‐cost, environmentally friendly continuous feed‐through process. The resulting composite derives a superior interlaminar shear strength from the microparticle‐modified fiber–matrix interfaces. The composite also demonstrates passive self‐sensing capabilities that produce electrical signals proportional to various dynamic loading events. Vibration and strain‐controlled experiments are performed on composite beams to quantify the sensitivity and power output as a function of input acceleration and strain. Furthermore, these composite‐generated electrical signals are used to identify in situ damage initiation for structural health monitoring to inform composite damage prior to structural failure. In brief, this truly multifunctional composite simultaneously displays a sensitivity of 0.5–2.6 mV g−1 at a resolution of 0.045–0.20g (g = gravitational acceleration), energy harvesting in the range of nW cc−1, and prediction of early damage by exhibiting 0.017–1.17 mV peaks in voltage–time history profiles while assuring ≈20% improved interlaminar shear strength.

NONLINEAR DYNAMIC CALIBRATION AND CORRECTION OF ACCELERATION SENSOR BASED ON ADAPTIVE NEURAL NETWORK

With the development of industrial technology, acceleration sensors have a wide range of applications. The application environment has strict requirements on acceleration sensor, which needs it to get accurate input and output response in complexity. According to the Hammerstein model, this paper studies the dynamic nonlinear relationship between the output voltage and the input acceleration of the acceleration sensor that can be divided into static nonlinear component and dynamic linear component. We combine the least square method with adaptive neural network to calculate the parameters of static nonlinear and dynamic linear components. The least square method is used to improve the training performance of the network and avoid the network falling into the local minimum of the traditional neural network. Experimental results show that compared with other methods, the proposed method has the advantages of less training steps and strong approximation ability, and the algorithm is less affected by external noise. This method can realize nonlinear system identification of acceleration sensor and provide reliable basis for compensation.

Feedforward control input generation method for a crane system with restrictions on drive system

This study proposes a feedforward (FF) control input generation method that can realize automatic anti-sway transport of a suspended load for a crane system with restrictions that the trolley can only accelerate or decelerate at a constant rate; the switching frequency of the acceleration input cannot be too high. First, a time-continuous FF control input is derived by the FF control input generation using the time-polynomial (FFT) method, which is the basis of our method. Next, the FF control input derived by the FFT method is approximated using the pulse width modulation (PWM) control input. In this case, the derived FF control input may be unable to suppress the sway of the suspended load because of the modeling error in deriving the FF control input and the quantization error in approximating the FF control input by the PWM control input. To solve these problems, we propose the update type FF control input generation using the time-polynomial (UFFT) method, which evaluates the residual sway at a constant time interval and updates the original FF control input derived by the FFT method. Finally, the effectiveness of the UFFT method is confirmed through simulations and experiments. Our method can achieve anti-sway transport that reduces the effects of modeling and quantization errors by setting the update frequency of the FF control input and the PWM frequency appropriately. It can search the FF control input that can suppress residual sway even when the control input switching frequency of the controller is not high.