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P E Boileau - One of the best experts on this subject based on the ideXlab platform.

  • influence of hand arm posture on biodynamic response of the human hand arm exposed to zh axis vibration
    International Journal of Industrial Ergonomics, 2006
    Co-Authors: Yasser Aldien, Subhash Rakheja, Pierre Marcotte, P E Boileau
    Abstract:

    Abstract The influence of hand–arm posture on the biodynamic responses under zh-axis vibration is investigated in terms of driving point Mechanical Impedance and absorbed power under various combinations of hand grip and push forces, handle sizes and excitation levels. Laboratory measurements of the biodynamic responses were performed on seven healthy male subjects exposed to two levels of broadband random vibration in the 8–1000 Hz frequency range using three instrumented cylindrical handles of different diameter (30, 40 and 50 mm), and different grip (10, 30 and 50 N) and push (25, 50 and 75 N) forces. The experiments involved grasping the handle with two different postures, consisting in flexed forearm with elbow angle of 90° and extended forearm with elbow angle of 180°, with wrist being in the neutral position for both postures. The results revealed remarkable effects of the hand–arm posture on both the Mechanical Impedance and the absorbed power characteristics. The low-frequency apparent mass magnitude of the hand–arm with the extended forearm posture was observed to be approximately three times than that with the flexed forearm posture. Furthermore, the effects of handle size, and push and grip forces on the biodynamic responses of the human hand–arm exposed to vibration were observed to be more significant for the extended forearm posture. This posture revealed considerably higher coupling with the vibrating handle and a damper-like behavior of the hand–arm system in the very low-frequency range. This posture also resulted in considerably higher power absorption than the flexed forearm posture for the majority of the combinations of hand forces considered. Depending on the handle size, excitation level, and hand forces, the total power absorbed by the hand–arm with an extended hand–arm could be up to 96% higher than that with the flexed elbow. From the results, it is evident that the hand–arm posture strongly affects the biodynamic response, when exposed to zh-axis vibration. Relevance to industry Operators assume considerable variations in the hand–arm posture while operating hand-held power tools. Such variations coupled with variations in the hand forces imparted on the tool handle could cause considerably different biodynamic responses of the hand–arm system. The current International Standard describes the range of idealized biodynamic response in terms of the driving-point Mechanical Impedance under a fixed posture involving 90° elbow angle (ISO-10068, 1998). The standard on the assessment of anti-vibration gloves also requires the same posture (ISO-10819, 1996). This study presents the effect of hand–arm posture on the biodynamic responses in terms of both driving-point Mechanical Impedance and power absorption by the hand–arm system. The influences of hand forces and handle sizes on both measures are also presented. The results of the study clearly suggest high significance of the hand–arm posture in view of the biodynamic responses. The results of the study attained on the driving-point Mechanical Impedance are expected to provide the vital knowledge and data for enhancing the current standard and its applications. The results attained on the influence of posture on the absorbed power characteristics of the hand–arm system are further expected to enhance our knowledge on the assessment of vibration exposure.

  • Mechanical Impedance and absorbed power of hand arm under xh axis vibration and role of hand forces and posture
    Industrial Health, 2005
    Co-Authors: Yasser Aldien, Subhash Rakheja, Pierre Marcotte, P E Boileau
    Abstract:

    The biodynamic responses of the hand-arm system under xh-axis vibration are investigated in terms of the driving point Mechanical Impedance (DPMI) and absorbed power in a laboratory study. For this purpose, seven healthy male subjects are exposed to two levels of random vibration in the 8-1,000 Hz frequency range, using three instrumented cylindrical handles of different diameters (30, 40 and 50 mm), and different combinations of grip (10, 30 and 50 N) and push (0, 25 and 50 N) forces. The experiments involve grasping the handle while adopting two different postures, involving elbow flexion of 90° and 180°, with wrist in the neutral position for both postures. The analyses of the results revealed peak DPMI magnitude and absorbed power responses near 25 Hz and 150 Hz, for majority of the test conditions considered. The frequency corresponding to the peak response increased with increasing hand forces. Unlike the absorbed power, the DPMI response was mostly observed to be insensitive to variations in the excitation magnitude. The handle diameter revealed obvious effects on the DPMI magnitude, specifically at frequencies above 250 Hz, which was not evident in the absorbed power due to relatively low velocity at higher frequencies. The influence of hand forces was also evident on the DPMI magnitude response particularly at frequencies above 100 Hz, while the effect of hand-arm posture on the DPMI magnitude was nearly negligible. The magnitude of power absorbed within the hand and arm was observed to be strongly dependent upon the excitation level over the entire frequency range, while the influence of hand-arm posture on the total absorbed power was observed to be important. The effect of variations in the hand forces on the absorbed power was relatively small for the bent elbow posture, while an increase in either the grip or the push force coupled with the extended arm posture resulted in considerably higher energy absorption. The results suggested that the handle size, hand-arm posture and hand forces, produce coupled effect on the biodynamic response of the hand-arm system.

  • a comparison of biodynamic models of the human hand arm system for applications to hand held power tools
    Journal of Sound and Vibration, 2002
    Co-Authors: Subhash Rakheja, Ren G Dong, A W Schopper, John Z. Wu, P E Boileau
    Abstract:

    Abstract The biodynamic response characteristics of various Mechanical models of the human hand and arm system, reported in the literature, are evaluated in terms of their driving-point Mechanical Impedance modulus and phase responses. The suitability of the reported models for applications in realizing a Mechanical simulator and assessment of vibration behavior of hand-held power tools is examined using three different criteria. These include the ability of the model to characterize the driving-point Mechanical Impedance of the human hand–arm system within the range of idealized values presented in ISO-10068 (1998); the magnitude of model deflection under a static feed force; and the vibration properties of the human hand and arm evaluated in terms of natural frequencies and damping ratios. From the relative evaluations of 12 different models, it is concluded that a vast majority of these models cannot be applied for the development of a Mechanical hand–arm simulator or the assessment of dynamic behavior of the coupled hand–tool system. The higher order models, with three and four degrees of freedom, in general, yield Impedance characteristics within the range of idealized values, but exhibit excessive static deflections. Moreover, these models involve very light masses (in the 1·2–4·8 g range), and exhibit either one or two vibration modes at frequencies below 10 Hz. The majority of the lower order models yield reasonable magnitudes of static deflections but relatively poor agreement with idealized values of driving-point Mechanical Impedance.

Chee Kiong Soh - One of the best experts on this subject based on the ideXlab platform.

  • electro Mechanical Impedance emi based incipient crack monitoring and critical crack identification of beam structures
    Research in Nondestructive Evaluation, 2014
    Co-Authors: Yee Yan Lim, Chee Kiong Soh
    Abstract:

    Fatigue-induced damage is often progressive and gradual in nature. Fatigue is often deteriorated by corrosion in ageing structures, creating maintenance problems, and even causing catastrophic failure. This ushers the development of structural health monitoring (SHM) and nondestructive evaluation (NDE) systems. Recent advent of smart materials applicable in SHM alleviates the shortcomings of the conventional techniques. Autonomous, real-time, remote monitoring becomes possible with the use of smart piezoelectric transducers. For instance, the electro-Mechanical Impedance (EMI) technique, employing piezoelectric transducers as collocated actuators and sensors, is known for its ability in damage detection and characterization. This article presents a series of lab-scale experimental tests and analysis to investigate the feasibility of fatigue crack detection and characterization employing the EMI technique. This study extends the work by Lim and Soh [1] to incorporate the phases involving crack initiation a...

  • structural Impedance based damage diagnosis by piezo transducers
    Earthquake Engineering & Structural Dynamics, 2003
    Co-Authors: Suresh Halla, Chee Kiong Soh
    Abstract:

    Although structural Mechanical Impedance is a direct representation of the structural parameters, its measurement is difficult at high frequencies owing to practical considerations. This paper presents a new method of damage diagnosis by means of changes in the structural Mechanical Impedance at high frequencies. The Mechanical Impedance is extracted from the electro-Mechanical admittance signatures of piezoelectric-ceramic (PZT) patches surface bonded to the structure using the electro-Mechanical Impedance (EMI) technique. The main feature of the newly developed approach is that both the real as well as the imaginary component of the admittance signature is used in damage quantification. A complex damage metric is proposed to quantify damage parametrically based on the extracted structural parameters, i.e. the equivalent single degree of freedom (SDOF) stiffness, the mass, and the damping associated with the drive point of the PZT patch. The proposed scheme eliminates the need for any a priori information about the phenomenological nature of the structure or any ‘model’ of the structural system. As proof of concept, the paper reports a damage diagnosis study conducted on a model reinforced concrete (RC) frame subjected to base vibrations on a shaking table. The proposed methodology was found to perform better than the existing damage quantification approaches, i.e. the low-frequency vibration methods as well as the traditional raw-signature based damage quantification in the EMI technique. Copyright © 2003 John Wiley & Sons, Ltd.

Gangbing Song - One of the best experts on this subject based on the ideXlab platform.

  • interfacial debonding detection in fiber reinforced polymer rebar reinforced concrete using electro Mechanical Impedance technique
    Structural Health Monitoring-an International Journal, 2018
    Co-Authors: Shuli Fan, Gangbing Song
    Abstract:

    For reinforced concrete structures, the use of fiber-reinforced polymer rebars to replace the steel reinforcement is a topic that is receiving increasing attention, especially where corrosion is a ...

  • A Novel Fractal Contact-ElectroMechanical Impedance Model for Quantitative Monitoring of Bolted Joint Looseness
    IEEE Access, 2018
    Co-Authors: Furui Wang, Siu Chun Michael Ho, Gangbing Song
    Abstract:

    Bolted joint are among the key components that enable the robust assembly of a wide variety of structures. However, due to wear and tear over time, bolted joint may loosen, and if not detected in its early stages, can lead to devastating results. A monitoring method that can detect bolted joint looseness prior to bolt failure will be essential for the continued operation of the host structure and depending on the situation, the safety of the occupants. Prior research has proven the electroMechanical Impedance method (EMI) to be an effective technique for detecting the loosening of bolted joints, however, EMI-based methods until now are focused on qualitative health monitoring, which can only provide limited information about the damage. Thus, this paper attempts to quantify EMI based methods through the integration of fractal contact theory, the result of which is a novel electroMechanical Impedance model for quantitative monitoring of bolted looseness. The method determines the effective Impedance of the bolted joint and is applied to develop the relationship between the electrical Impedance of a piezoceramic patch installed on the joint and the Mechanical Impedance of the bolted joint. The Mechanical Impedance of the bolted joint under various preloads is computed by using the fractal contact theory. Then, the bolted looseness can be monitored quantitatively. At last, a set of verification tests under different applied preload of bolted joint are conducted to verify the validity of the proposed model in this paper.

Victor Giurgiutiu - One of the best experts on this subject based on the ideXlab platform.

  • Title: Electro-Mechanical Impedance Method for Crack Detection in Thin
    2015
    Co-Authors: Wall Structures, N. Zagrai, Victor Giurgiutiu
    Abstract:

    The Electro-Mechanical (E/M) Impedance method has achieved acceptance among NDE methods due to its relative simplicity, applicability to complex structures, and low cost of active piezoelectric elements. Thus, allow one to identify the structural dynamics directly by obtaining its E/M Impedance or admittance signatures. Previous work reported on this method contained little theoretical work but described many practical applications. The scope of presented research was to extend the positive results obtained for 1-D structure onto 2-D thin-wall structures with circular symmetry. Theoretical analysis was analytically performed on simple geometries (circular plates) subjected to particular set of boundary conditions. The experimental results shown that E/M Impedance (or admittance) spectrum accurately identify the natural frequency spectrum of the specimens manufactured from the aircraft-grade thin-gage material. Changes in the E/M Impedance spectrum due to presence of crack were investigated. The dependence of the frequency spectrum on crack location was studied. The results show changing in E/M Impedance spectrum due to damage presence. Additional recommendations are given to improve applications of the E/M Impedance method for aging aircraft-type structures to detect incipient cracks and corrosion damage. 1

  • electro Mechanical Impedance method for crack detection in thin plates
    Journal of Intelligent Material Systems and Structures, 2001
    Co-Authors: Andrei Zagrai, Victor Giurgiutiu
    Abstract:

    This paper describes the utilization of Electro-Mechanical (E/M) Impedance method for structural health monitoring of thin plates. The method allows the direct identification of structural dynamics by obtaining its E/M Impedance or admittance signatures. The analytical model for two-dimensions structure was developed and verified with experiments. Good matching of experimental results and calculated spectra was obtained for axial and flexural components. The ability of the method to identify the presence of damage was investigated by performing an experiment where the damage in the form of crack was simulated with An EDM slit placed at various distances from the sensor. It was found that the crack presence dramatically modifies the E/M Impedance spectrum and this modification decreases as the distance between the sensor and the crack increases. Several overall-statistics damage metrics, which may be used for on-line structural heath monitoring, were investigated. Among these candidate damage metrics, the α-th power of the correlation coefficient deviation, CCD α , 3 < α < 7, used in the high frequency band 300-450 kHz, was found to be most successful. Careful selection of the high frequency band and proper choice of the appropriate damage metric were found to be essential for successful damage detection and structural health monitoring.

  • title electro Mechanical Impedance method for crack detection in thin wall structures
    2001
    Co-Authors: Andrei Zagrai, Victor Giurgiutiu
    Abstract:

    The Electro-Mechanical (E/M) Impedance method has achieved acceptance among NDE methods due to its relative simplicity, applicability to complex structures, and low cost of active piezoelectric elements. Thus, allow one to identify the structural dynamics directly by obtaining its E/M Impedance or admittance signatures. Previous work reported on this method contained little theoretical work but described many practical applications. The scope of presented research was to extend the positive results obtained for 1-D structure onto 2-D thin-wall structures with circular symmetry. Theoretical analysis was analytically performed on simple geometries (circular plates) subjected to particular set of boundary conditions. The experimental results shown that E/M Impedance (or admittance) spectrum accurately identify the natural frequency spectrum of the specimens manufactured from the aircraft-grade thin-gage material. Changes in the E/M Impedance spectrum due to presence of crack were investigated. The dependence of the frequency spectrum on crack location was studied. The results show changing in E/M Impedance spectrum due to damage presence. Additional recommendations are given to improve applications of the E/M Impedance method for aging aircraft-type structures to detect incipient cracks and corrosion damage. 1. INTRODUCTION In recent years, the damage detection with E/M Impedance method has gained increased attention. The method uses small-size piezoelectric active sensors intimately bonded to an existing structure, or embedded into a new composite construction. Experimental demonstrations have shown that the real part of the high-frequency Impedance spectrum is directly affected by the presence of damage or defects in the monitored structure (Figure 1). The pioneering work on utilization of E/M Impedance method for structural health monitoring was presented by Liang et al. (1994) who performed the coupled

Neville Hogan - One of the best experts on this subject based on the ideXlab platform.

  • Modulating hip stiffness with a robotic exoskeleton immediately changes gait
    2020 IEEE International Conference on Robotics and Automation (ICRA), 2020
    Co-Authors: Jongwoo Lee, Haley R. Warren, Vibha Agarwal, Meghan E. Huber, Neville Hogan
    Abstract:

    Restoring healthy kinematics is a critical component of assisting and rehabilitating impaired locomotion. Here we tested whether spatiotemporal gait patterns can be modulated by applying Mechanical Impedance to hip joints. Using the Samsung GEMS-H exoskeleton, we emulated a virtual spring (positive and negative) between the user's legs. We found that applying positive stiffness with the exoskeleton decreased stride time and hip range of motion for healthy subjects during treadmill walking. Conversely, the application of negative stiffness increased stride time and hip range of motion. These effects did not vary over long nor short repeated exposures to applied stiffness. In addition, minimal transient behavior was observed in spatiotemporal measures of gait when the stiffness controller transitioned between on and off states. These results suggest that changes in gait behavior induced by applying hip stiffness were purely a Mechanical effect. Together, our findings indicate that applying Mechanical Impedance using lower-limb assistive devices may be an effective, minimally-encumbering intervention to restore healthy gait patterns.

  • ankle Mechanical Impedance under muscle fatigue
    American Society of Mechanical Engineers (ASME), 2013
    Co-Authors: Shuo Wang, Hyunglae Lee, Neville Hogan
    Abstract:

    This paper reports preliminary results on the effects of ankle muscle fatigue on ankle Mechanical Impedance. The experiment was designed to induce fatigue in the Tibialis Anterior and Triceps Surae muscle group by asking subjects to perform isometric contractions against a constant ankle torque generated by the Anklebot, a backdriveable robot that interacts with the ankle in two degrees of freedom. Median frequencies of surface electromyographic signals collected from Tibialis Anterior and Triceps Surae muscle group were evaluated to assess muscle fatigue. Using a standard multi-input and multi-output stochastic Impedance identification method, multivariable ankle Mechanical Impedance was measured in two degrees of freedom under muscle fatigue. Preliminary results indicate that, for both Tibialis Anterior and Triceps Surae muscle group, ankle Mechanical Impedance decreases in both the dorsi-plantarflexion and inversion-eversion directions under muscle fatigue. This finding suggests that decreasing ankle Impedance with muscle fatigue may help to develop joint support systems to prevent ankle injuries caused by muscle fatigue.Copyright © 2013 by ASME

  • stochastic estimation of arm Mechanical Impedance during robotic stroke rehabilitation
    IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2007
    Co-Authors: J J Palazzolo, Hermano Igo Krebs, Mark Ferraro, Daniel V Lynch, Bruce T Volpe, Neville Hogan
    Abstract:

    This paper presents a stochastic method to estimate the multijoint Mechanical Impedance of the human arm suitable for use in a clinical setting, e.g., with persons with stroke undergoing robotic rehabilitation for a paralyzed arm. In this context, special circumstances such as hypertonicity and tissue atrophy due to disuse of the hemiplegic limb must be considered. A low-Impedance robot was used to bring the upper limb of a stroke patient to a test location, generate force perturbations, and measure the resulting motion. Methods were developed to compensate for input signal coupling at low frequencies apparently due to human-machine interaction dynamics. Data was analyzed by spectral procedures that make no assumption about model structure. The method was validated by measuring simple Mechanical hardware and results from a patient's hemiplegic arm are presented