Pub Date : 2023-04-22DOI: 10.3390/vibration6020024
F. Greco, F. Quinzi, Katia Folino, M. Spadafora, Loretta Francesca Cosco, M. Tarsitano, G. Emerenziani
This study analysed the acute effects of whole-body vibration (WBV) on quadriceps isometric muscular endurance. Fifteen healthy middle-aged males performed an endurance isometric strength test after three different warm-up conditions: static half squat plus WBV (HSV), static half squat without WBV (HS), and control condition (CC). The endurance isometric strength test consisted of 10 maximal isometric contractions held for 4 s and interspersed by 2 s of rest between each repetition. Rate of Perceived Exertion (RPE) was assessed after warm-up (RPE1) and at the end of the testing session (RPE2). During each testing session, participant’s heart rate (HR) was continuously recorded. For each trial, the mean force across the 10 repetitions and fatigue index were evaluated. Mean force was significantly higher (p < 0.01) in CC than in the other two conditions. Both RPE1 and RPE2 were significantly lower (p < 0.01) in CC than HSV and HS condition. Warm-up HR and the mean testing session HR were significantly lower in CC than the other two conditions (p < 0.01). No significant differences were observed in fatigue index between conditions (p > 0.05) or in HR during the endurance protocol. Performing half-squat with or without vibration stimuli does not increase isometric muscular endurance and does not influence fatigue index.
{"title":"Acute Effects of Whole-Body Vibration on Quadriceps Isometric Muscular Endurance in Middle-Aged Adults: A Pilot Study","authors":"F. Greco, F. Quinzi, Katia Folino, M. Spadafora, Loretta Francesca Cosco, M. Tarsitano, G. Emerenziani","doi":"10.3390/vibration6020024","DOIUrl":"https://doi.org/10.3390/vibration6020024","url":null,"abstract":"This study analysed the acute effects of whole-body vibration (WBV) on quadriceps isometric muscular endurance. Fifteen healthy middle-aged males performed an endurance isometric strength test after three different warm-up conditions: static half squat plus WBV (HSV), static half squat without WBV (HS), and control condition (CC). The endurance isometric strength test consisted of 10 maximal isometric contractions held for 4 s and interspersed by 2 s of rest between each repetition. Rate of Perceived Exertion (RPE) was assessed after warm-up (RPE1) and at the end of the testing session (RPE2). During each testing session, participant’s heart rate (HR) was continuously recorded. For each trial, the mean force across the 10 repetitions and fatigue index were evaluated. Mean force was significantly higher (p < 0.01) in CC than in the other two conditions. Both RPE1 and RPE2 were significantly lower (p < 0.01) in CC than HSV and HS condition. Warm-up HR and the mean testing session HR were significantly lower in CC than the other two conditions (p < 0.01). No significant differences were observed in fatigue index between conditions (p > 0.05) or in HR during the endurance protocol. Performing half-squat with or without vibration stimuli does not increase isometric muscular endurance and does not influence fatigue index.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41645908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-12DOI: 10.3390/vibration6020023
T. Schröder, A. Lindenmann, S. Matthiesen
This manuscript investigates the rotational mechanical impedance of the human hand–arm system with respect to vibration excitation around the gripping axis of the hand under the influence of body posture, gripping force, and push force. Knowledge of rotational mechanical impedance is required for deriving models of hand–arm biodynamics. These models are used in the validation of power tools to predict further vibrational human–machine interactions. In the current state of research, such models exist for translational but not rotational vibration excitation. Consequently, this study investigates the properties of a hand–arm system with respect to rotational vibration excitation. In the study, the rotational impedance of the hand–arm systems of 13 adults was measured at various gripping and push forces applied in different body postures. The setup of the test used in this study consisted of a shaker that applied rotational vibrations at certain frequencies to the subjects’ hand–arm systems via a cylindrical handle. The results of the study indicate a spring–damper dynamic of the hand–arm system. The gripping force strongly influences the magnitude of rotational impedance across the frequency spectrum. Regarding push force and posture, no corresponding influence could be determined. The results suggest that the frictional contact between the hand and handle might confer a damping effect.
{"title":"Influence of Coupling Forces and Body Posture on the Rotational Hand–Arm Impedance in yh Direction","authors":"T. Schröder, A. Lindenmann, S. Matthiesen","doi":"10.3390/vibration6020023","DOIUrl":"https://doi.org/10.3390/vibration6020023","url":null,"abstract":"This manuscript investigates the rotational mechanical impedance of the human hand–arm system with respect to vibration excitation around the gripping axis of the hand under the influence of body posture, gripping force, and push force. Knowledge of rotational mechanical impedance is required for deriving models of hand–arm biodynamics. These models are used in the validation of power tools to predict further vibrational human–machine interactions. In the current state of research, such models exist for translational but not rotational vibration excitation. Consequently, this study investigates the properties of a hand–arm system with respect to rotational vibration excitation. In the study, the rotational impedance of the hand–arm systems of 13 adults was measured at various gripping and push forces applied in different body postures. The setup of the test used in this study consisted of a shaker that applied rotational vibrations at certain frequencies to the subjects’ hand–arm systems via a cylindrical handle. The results of the study indicate a spring–damper dynamic of the hand–arm system. The gripping force strongly influences the magnitude of rotational impedance across the frequency spectrum. Regarding push force and posture, no corresponding influence could be determined. The results suggest that the frictional contact between the hand and handle might confer a damping effect.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44144191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-03DOI: 10.3390/vibration6020022
Davide Raffaele, E. Rustighi, T. Waters
The Semi-Analytical Finite-Element (SAFE) method represents one of the most established numerical approaches for predicting the propagation of elastic waves in one-dimensional structures of arbitrary cross-sections. Its implementation in the commercial finite-element software COMSOL Multiphysics has been proposed in recent years; however, it is limited to only the free wave propagation for computing dispersion curves. To overcome this limitation, this paper proposes an extension of this approach that combines COMSOL and its Livelink for Matlab tool. This enables the extraction from COMSOL of the assembled mass and stiffness SAFE matrices to solve problems of both free and forced wave propagation in the Matlab environment. The resulting customised software takes advantage of both the potential of commercial FE software and the power of Matlab without worrying about compatibility issues. A model of a simply supported plate strip and that of a more complex geometry are implemented to validate, respectively, the SAFE matrix extraction procedure and the implemented forced response formulation. The results agree well with corresponding analytical and numerical results validating the proposed implementation of the SAFE method.
半解析有限元法(SAFE)是预测弹性波在任意截面一维结构中传播的最成熟的数值方法之一。它在商业有限元软件COMSOL Multiphysics中的实现是近年来提出的;然而，色散曲线的计算仅限于自由波的传播。为了克服这一限制，本文提出了将COMSOL及其Livelink for Matlab工具相结合的方法的扩展。这使得从COMSOL中提取组装的质量和刚度SAFE矩阵能够在Matlab环境中解决自由和强制波传播的问题。由此产生的定制软件充分利用了商业有限元软件的潜力和Matlab的强大功能，而无需担心兼容性问题。简支板带和更复杂几何形状的模型分别用于验证SAFE矩阵提取程序和实现的强制响应公式。计算结果与相应的解析和数值结果吻合较好，验证了该方法的可行性。
{"title":"Semi-Analytical Finite-Element Analysis for Free and Forced Wave Propagation Using COMSOL and LiveLink for Matlab","authors":"Davide Raffaele, E. Rustighi, T. Waters","doi":"10.3390/vibration6020022","DOIUrl":"https://doi.org/10.3390/vibration6020022","url":null,"abstract":"The Semi-Analytical Finite-Element (SAFE) method represents one of the most established numerical approaches for predicting the propagation of elastic waves in one-dimensional structures of arbitrary cross-sections. Its implementation in the commercial finite-element software COMSOL Multiphysics has been proposed in recent years; however, it is limited to only the free wave propagation for computing dispersion curves. To overcome this limitation, this paper proposes an extension of this approach that combines COMSOL and its Livelink for Matlab tool. This enables the extraction from COMSOL of the assembled mass and stiffness SAFE matrices to solve problems of both free and forced wave propagation in the Matlab environment. The resulting customised software takes advantage of both the potential of commercial FE software and the power of Matlab without worrying about compatibility issues. A model of a simply supported plate strip and that of a more complex geometry are implemented to validate, respectively, the SAFE matrix extraction procedure and the implemented forced response formulation. The results agree well with corresponding analytical and numerical results validating the proposed implementation of the SAFE method.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43064391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.3390/vibration6020021
J. Tatsuno, S. Maeda
This study aims to investigate the effects of whole-body vibration (WBV) exposure on the disturbance of standing balance function assuming that the cause of slip, trip and fall accidents in the land transportation industry is related to WBV exposure when traveling in vehicles. In the experiment, ten participants underwent 60 min of virtual driving in a driving simulator (DS) for WBV exposure. In addition, standing balance measurements were conducted before exposure, immediately after exposure, 2 min after exposure and 4 min after exposure. Four conditions were considered by combining two magnitudes of WBV exposure and the driver and passenger conditions. This study focused on two indexes of standing balance, namely, total length and enveloped area and the rate of change relative to the value before the vibration exposure was calculated. The rate of change remained almost constant at 1.0 in the control condition without vibration exposure, whereas that under vibration exposure conditions varied. Interestingly, the rate of change at 2 min after exposure remained high in the driver condition, but it decreased to almost 1.0 in the passenger condition. Since no difference appeared in the vibration acceleration measured at the seating surface between the driver and passenger conditions, it was believed that the difference between the driving and passenger conditions was related to fatigue caused by the accelerator-pedal operation. As a result of considering the percentage of the standing balance that returned to 1.0 after 4 min in most conditions, this study proposed that a rest period of several minutes be allowed from the experiment in which the participants were exposed to vibration at 0.5m/s2 rms for 60 min at the DS. Further basic experiments will be conducted to introduce another WBV exposure assessment, including loss of standing balance as a health indicator, to ISO 2631-1.
{"title":"Effect of Whole-Body Vibration Exposure in Vehicles on Static Standing Balance after Riding","authors":"J. Tatsuno, S. Maeda","doi":"10.3390/vibration6020021","DOIUrl":"https://doi.org/10.3390/vibration6020021","url":null,"abstract":"This study aims to investigate the effects of whole-body vibration (WBV) exposure on the disturbance of standing balance function assuming that the cause of slip, trip and fall accidents in the land transportation industry is related to WBV exposure when traveling in vehicles. In the experiment, ten participants underwent 60 min of virtual driving in a driving simulator (DS) for WBV exposure. In addition, standing balance measurements were conducted before exposure, immediately after exposure, 2 min after exposure and 4 min after exposure. Four conditions were considered by combining two magnitudes of WBV exposure and the driver and passenger conditions. This study focused on two indexes of standing balance, namely, total length and enveloped area and the rate of change relative to the value before the vibration exposure was calculated. The rate of change remained almost constant at 1.0 in the control condition without vibration exposure, whereas that under vibration exposure conditions varied. Interestingly, the rate of change at 2 min after exposure remained high in the driver condition, but it decreased to almost 1.0 in the passenger condition. Since no difference appeared in the vibration acceleration measured at the seating surface between the driver and passenger conditions, it was believed that the difference between the driving and passenger conditions was related to fatigue caused by the accelerator-pedal operation. As a result of considering the percentage of the standing balance that returned to 1.0 after 4 min in most conditions, this study proposed that a rest period of several minutes be allowed from the experiment in which the participants were exposed to vibration at 0.5m/s2 rms for 60 min at the DS. Further basic experiments will be conducted to introduce another WBV exposure assessment, including loss of standing balance as a health indicator, to ISO 2631-1.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47913931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-25DOI: 10.3390/vibration6020020
M. Keikha, J. T. Kahnamouei, M. Moallem
Reduction or suppression of microphonic interference in radio frequency (RF) cavities, such as those used in Electron Linear Accelerators, is necessary to precisely control accelerating fields. In this paper, we investigate modeling the cavity as a cylindrical shell and present its free vibration analysis along with an appropriate control scheme to suppress vibrations. To this end, we first obtain an analytical mechanical dynamic model of a nine-cell cavity using a modified Fourier-Ritz method that provides a unified solution for cylindrical shell systems with general boundary conditions. The model is then verified using the ANSYS software in terms of a comparison of eigenfrequencies which prove to be identical to the proposed model. We also present an active observer-based vibration control scheme to suppress the dominant mechanical modes of the cavity. The control system performance is investigated using simulations.
{"title":"Radio Frequency Cavity’s Analytical Model and Control Design","authors":"M. Keikha, J. T. Kahnamouei, M. Moallem","doi":"10.3390/vibration6020020","DOIUrl":"https://doi.org/10.3390/vibration6020020","url":null,"abstract":"Reduction or suppression of microphonic interference in radio frequency (RF) cavities, such as those used in Electron Linear Accelerators, is necessary to precisely control accelerating fields. In this paper, we investigate modeling the cavity as a cylindrical shell and present its free vibration analysis along with an appropriate control scheme to suppress vibrations. To this end, we first obtain an analytical mechanical dynamic model of a nine-cell cavity using a modified Fourier-Ritz method that provides a unified solution for cylindrical shell systems with general boundary conditions. The model is then verified using the ANSYS software in terms of a comparison of eigenfrequencies which prove to be identical to the proposed model. We also present an active observer-based vibration control scheme to suppress the dominant mechanical modes of the cavity. The control system performance is investigated using simulations.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46186840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-11DOI: 10.3390/vibration6010019
Junjie Zhao, Peng Liu, D. Leng, Haoyu Zhan, Guangrui Luan, D. Ning, Jianqiang Yu
Seat suspension plays a vital role in improving riding comfort and protecting drivers’ health. This paper develops semi-active seat suspension that equips a controllable electromagnetic damper (EMD) and proposes a prescribed performance control-based semi-active vibration controller with experimental validation. The semi-active EMD mainly consists of a permanent magnet synchronous motor, a ball screw, a three-phase rectifier, and a controllable external resistor, which can vary its damping from 90 to 800 N·s/m by tuning the controllable external resistor in real-time. The EMD is applied to seat suspension, and a semi-active controller is proposed for the EMD seat suspension. In order to control the seat suspension vibration, a prescribed performance method is applied to obtain a desired control force and then a force-tracking strategy is designed to make the EMD track the desired control force. Finally, the semi-active seat suspension with the proposed controller is tested in experiments with different vibration conditions. The semi-active seat suspension performs excellently for the bump, sine wave and random vibration. The root mean square (RMS) acceleration, the frequency-weighted RMS acceleration and the acceleration’s fourth power vibration dose value were reduced by 17.5%, 39.9%, and 25.4%, respectively, in the random vibration, compared with a passive system.
{"title":"Prescribed Performance Control-Based Semi-Active Vibration Controller for Seat Suspension Equipped with an Electromagnetic Damper","authors":"Junjie Zhao, Peng Liu, D. Leng, Haoyu Zhan, Guangrui Luan, D. Ning, Jianqiang Yu","doi":"10.3390/vibration6010019","DOIUrl":"https://doi.org/10.3390/vibration6010019","url":null,"abstract":"Seat suspension plays a vital role in improving riding comfort and protecting drivers’ health. This paper develops semi-active seat suspension that equips a controllable electromagnetic damper (EMD) and proposes a prescribed performance control-based semi-active vibration controller with experimental validation. The semi-active EMD mainly consists of a permanent magnet synchronous motor, a ball screw, a three-phase rectifier, and a controllable external resistor, which can vary its damping from 90 to 800 N·s/m by tuning the controllable external resistor in real-time. The EMD is applied to seat suspension, and a semi-active controller is proposed for the EMD seat suspension. In order to control the seat suspension vibration, a prescribed performance method is applied to obtain a desired control force and then a force-tracking strategy is designed to make the EMD track the desired control force. Finally, the semi-active seat suspension with the proposed controller is tested in experiments with different vibration conditions. The semi-active seat suspension performs excellently for the bump, sine wave and random vibration. The root mean square (RMS) acceleration, the frequency-weighted RMS acceleration and the acceleration’s fourth power vibration dose value were reduced by 17.5%, 39.9%, and 25.4%, respectively, in the random vibration, compared with a passive system.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45264736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-10DOI: 10.3390/vibration6010018
Minoru Sasaki, Joseph K. Muguro, Waweru Njeri, A. Doss
This paper presents a 2-link, 2-DOF flexible manipulator control using an inverse feedforward controller and an adaptive notch filter with a direct strain feedback controller. In the flexible manipulator, transient and residue vibrations inhibit the full potential of the manipulator. Vibrations caused by abrupt changes in the direction of the links are referred to as transient vibrations, whereas residual vibrations occur when the arm takes too long to settle after engaging in the intended task. The feedforward adaptive notch filter will reduce transient vibration caused by the manipulator arm beginning and halting suddenly, while the strain feedback will assure the quick decay of leftover vibrations. Maple, Maplesim, and MATLAB tools were used to model the manipulator and create the inverse controller and adaptive notch filter. The experiments took place in the dSPACE control desk environment. The experimental results of the spectral power of strain resulting from the two strategies are compared. From the results, the adaptive notch filter control had over an 80% improvement in the reduction in resonant frequencies that contribute to vibration. The results confirmed the feasibility of the approach, characterized by very minimal transient vibrations and a quick settling of the end effector.
{"title":"Adaptive Notch Filter in a Two-Link Flexible Manipulator for the Compensation of Vibration and Gravity-Induced Distortion","authors":"Minoru Sasaki, Joseph K. Muguro, Waweru Njeri, A. Doss","doi":"10.3390/vibration6010018","DOIUrl":"https://doi.org/10.3390/vibration6010018","url":null,"abstract":"This paper presents a 2-link, 2-DOF flexible manipulator control using an inverse feedforward controller and an adaptive notch filter with a direct strain feedback controller. In the flexible manipulator, transient and residue vibrations inhibit the full potential of the manipulator. Vibrations caused by abrupt changes in the direction of the links are referred to as transient vibrations, whereas residual vibrations occur when the arm takes too long to settle after engaging in the intended task. The feedforward adaptive notch filter will reduce transient vibration caused by the manipulator arm beginning and halting suddenly, while the strain feedback will assure the quick decay of leftover vibrations. Maple, Maplesim, and MATLAB tools were used to model the manipulator and create the inverse controller and adaptive notch filter. The experiments took place in the dSPACE control desk environment. The experimental results of the spectral power of strain resulting from the two strategies are compared. From the results, the adaptive notch filter control had over an 80% improvement in the reduction in resonant frequencies that contribute to vibration. The results confirmed the feasibility of the approach, characterized by very minimal transient vibrations and a quick settling of the end effector.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42530735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-03DOI: 10.3390/vibration6010017
H. Jafari, R. Sedaghati
This paper is concerned with the free and forced vibration responses of a magneto/electroactive dielectric elastomer, emphasizing the chaotic phenomena. The dielectric elastomers under external magnetic and electrical excitations undergo large elastic deformation. The magnetodielectric elastomer is modeled based on the Gent–Gent strain energy function to incorporate the influence of the second invariant and the strain stiffening. The viscoelasticity of the active polymer is also considered in the form of Rayleigh’s dissipation function. The equation of motion is governed with the aid of the Lagrangian equation in terms of a physical quantity, namely, the stretch of the elastomer. An energy-based approach is utilized to re-evaluate the static and DC voltage instabilities of the resonator. Time-stretch response (time history behavior), phase plane diagram, Poincaré map, and fast Fourier transform are numerically obtained and presented to explore the chaotic oscillation behavior of the active polymer actuators. The results reveal that the magnetic field may tune the stability and instability regions of the active polymeric membrane. It has also been shown that the applied magnetic field may lead to chaotic vibration responses when a sinusoidal voltage is applied simultaneously to the system. The results presented in this paper can be effectively used to design magnetic and electrical soft robotic actuators and elastomer membranes under electrical and magnetic stimulants.
{"title":"Free and Forced Vibration Behaviors of Magnetodielectric Effect in Magnetorheological Elastomers","authors":"H. Jafari, R. Sedaghati","doi":"10.3390/vibration6010017","DOIUrl":"https://doi.org/10.3390/vibration6010017","url":null,"abstract":"This paper is concerned with the free and forced vibration responses of a magneto/electroactive dielectric elastomer, emphasizing the chaotic phenomena. The dielectric elastomers under external magnetic and electrical excitations undergo large elastic deformation. The magnetodielectric elastomer is modeled based on the Gent–Gent strain energy function to incorporate the influence of the second invariant and the strain stiffening. The viscoelasticity of the active polymer is also considered in the form of Rayleigh’s dissipation function. The equation of motion is governed with the aid of the Lagrangian equation in terms of a physical quantity, namely, the stretch of the elastomer. An energy-based approach is utilized to re-evaluate the static and DC voltage instabilities of the resonator. Time-stretch response (time history behavior), phase plane diagram, Poincaré map, and fast Fourier transform are numerically obtained and presented to explore the chaotic oscillation behavior of the active polymer actuators. The results reveal that the magnetic field may tune the stability and instability regions of the active polymeric membrane. It has also been shown that the applied magnetic field may lead to chaotic vibration responses when a sinusoidal voltage is applied simultaneously to the system. The results presented in this paper can be effectively used to design magnetic and electrical soft robotic actuators and elastomer membranes under electrical and magnetic stimulants.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48701073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-21DOI: 10.3390/vibration6010015
D. Friso
In the nursery sector, the transport and planting of trees must occur with the roots wrapped in a ball of the original earth. The cutting of the original soil can be carried out with a semicircular vibrating blade moved by an oscillator mounted on a self-propelled machine. The oscillator produces an excitation torque supplied to the blade together with the soil cutting torque. The advantage of the vibrating blade is a reduction in the cutting torque of up to 70%. However, to correctly design the oscillator, we need to investigate the link between the maximum displacement of the blade, the maximum oscillation velocity, the cutting velocity, the dry friction, the excitation torque, the elastic torque, the cutting torque, the required power, the required energy, and the excitation frequency. The maximum displacement and velocity ratio need to have the right values to minimize the cutting torque and to avoid the springs reaching the end of stroke; otherwise, vibrations are transmitted to the machine and to the operator. Therefore, starting from the forced oscillation differential equation and using an approximate solution method developed by Den Hartog, along with some experimental data, a mathematical model was constructed to optimize the oscillator design. After construction, it was coupled to blades of various diameters (0.6, 0.9, and 1.2 m) to undergo experimental tests. The soil cutting tests highlighted the achievement of the above objectives and, at the same time, confirmed the validity of the Den Hartog equations used to calculate the phase lag and the maximum displacement, resulting in an average error of 4.4% and a maximum error of 6.4%.
{"title":"Study of an Optimized Mechanical Oscillator for the Forced Vibration of the Soil Cutting Blade","authors":"D. Friso","doi":"10.3390/vibration6010015","DOIUrl":"https://doi.org/10.3390/vibration6010015","url":null,"abstract":"In the nursery sector, the transport and planting of trees must occur with the roots wrapped in a ball of the original earth. The cutting of the original soil can be carried out with a semicircular vibrating blade moved by an oscillator mounted on a self-propelled machine. The oscillator produces an excitation torque supplied to the blade together with the soil cutting torque. The advantage of the vibrating blade is a reduction in the cutting torque of up to 70%. However, to correctly design the oscillator, we need to investigate the link between the maximum displacement of the blade, the maximum oscillation velocity, the cutting velocity, the dry friction, the excitation torque, the elastic torque, the cutting torque, the required power, the required energy, and the excitation frequency. The maximum displacement and velocity ratio need to have the right values to minimize the cutting torque and to avoid the springs reaching the end of stroke; otherwise, vibrations are transmitted to the machine and to the operator. Therefore, starting from the forced oscillation differential equation and using an approximate solution method developed by Den Hartog, along with some experimental data, a mathematical model was constructed to optimize the oscillator design. After construction, it was coupled to blades of various diameters (0.6, 0.9, and 1.2 m) to undergo experimental tests. The soil cutting tests highlighted the achievement of the above objectives and, at the same time, confirmed the validity of the Den Hartog equations used to calculate the phase lag and the maximum displacement, resulting in an average error of 4.4% and a maximum error of 6.4%.","PeriodicalId":75301,"journal":{"name":"Vibration","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47275525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-17DOI: 10.3390/vibration6010014
Md Roman Bhuiyan, J. Uddin
In order to evaluate final quality, nondestructive testing techniques for finding bearing flaws have grown in favor. The precision of image processing-based vision-based technology has greatly improved for defect identification, inspection, and classification. Deep Transfer Learning (DTL), a kind of machine learning, combines the superiority of Transfer Learning (TL) for knowledge transfer with the benefits of Deep Learning (DL) for feature representation. As a result, the discipline of Intelligent Fault Diagnosis has extensively developed and researched DTL approaches. They can improve the robustness, reliability, and usefulness of DL-based fault diagnosis techniques (IFD). IFD has been the subject of several thorough and excellent studies, although most of them have appraised important research from an algorithmic standpoint, neglecting real-world applications. DTL-based IFD strategies have also not yet undergone a full evaluation. It is necessary and imperative to go through the relevant DTL-based IFD publications in light of this. Readers will be able to grasp the most cutting-edge concepts and develop practical solutions to any IFD challenges they may encounter by doing this. The theory behind DTL is briefly discussed before describing how transfer learning algorithms may be included into deep learning models. This research study looks at a number of vision-based methods for defect detection and identification utilizing vibration acoustic sensor data. The goal of this review is to assess where vision inspection system research is right now. In this respect, image processing as well as deep learning, machine learning, transfer learning, few-shot learning, and light-weight approach and its selection were explored. This review addresses the creation of defect classifiers and vision-based fault detection systems.
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