Vibration Response of Manual Wheelchairs According to Loads, Propulsion Methods, Speeds, and Ground Floor Types

Other funding : doctoral allowance from the Sorbonne University of Paris Nord (France)Manual wheelchair (MWC) users are daily exposed to vibration during propulsion. The impact of such exposure on the MWC user’s health has yet to be proven. To date, no agreement has been reached, presumably on the account of the wide variety of experimental parameters that need to be controlled. A possible solution relies on the implementation of a User/MWC model to point out the effect of propelling conditions (MWC loads, propulsion methods, speeds, and ground floor types) on the vibration exposure and eventually on the MWC user’s health. To feed such a model, the evaluation of the MWC vibration response during propulsion is required. Following a necessary MWC experimental modal analysis under laboratory conditions, this study presents the vibration response of an MWC under various propelling conditions. For each investigated condition, the identified set of modal parameters was provided and the effect on the MWC response to vibration at the User/MWC interfaces was highlighted. Results mostly underline that the response to vibration is highly dependent on the propelling conditions. The speed and the ground floor type greatly affect the vibration response: doubling speed and increasing ground surface roughness imply threefold and eightfold vibration levels, respectively. Finally, the main outcome is that an empty MWC or an MWC loaded with a dummy generates vibration outside the range measured for an MWC loaded with a human body, resulting in a lower frequency content and an almost two-fold vibration level increase. The findings of this study will help enhance the understanding of the health risks that wheelchair users encounter as a result of vibrations

Vibration Transmission during Manual Wheelchair Propulsion: A Systematic Review

Manual wheelchair (MWC) propulsion can expose the user to significant vibration. Human body exposure to certain vibrations can be detrimental to health, and a source of discomfort and fatigue. Therefore, identifying vibration exposure and key parameters influencing vibration transmissibility during MWC propulsion is crucial to protect MWC users from vibration risks. For that purpose, a systematic review using PRISMA recommendations was realized to synthesize the current knowledge regarding vibration transmissibility during MWC propulsion. The 35 retrieved articles were classified into three groups: Vibration content, parameters influencing vibration transmission, and vibration transmission modeling. The review highlighted that MWC users experience vibration in the frequency range detrimental/uncomfortable for human vibration transmission during MWC propulsion depends on many parameters and is still scarcely studied and understood. A modeling and simulation approach would be an interesting way to assist physicians in selecting the best settings for a specific user, but many works (modeling, properties identification, etc.) must be done before being effective for clinical and industrial purposes

3D propagation of the shock-induced vibrations through the whole lower-limb during running

Shock-induced vibrations to the feet have been related to the feel of comfort, the biomechanical control of performance, and the risk of fatigue or injury. Up to recently, the complexity of measuring the human biodynamic response to vibration exposure implied to focus most of the research on the axial acceleration at the tibia. Using wireless three-dimensional accelerometers, this paper investigates the propagation of shock-induced vibrations through the whole lower-limb during running in the temporal and the spectral domains. Results indicated that the vibrations were not consistent across the lower-limb, showing various spatial and spectral distributions of energy. The amount of energy was not constantly decreasing from the distal to the proximal extremity of the runner’s lower-limb, especially regarding the lateral epicondyle of the femur. Vibrations in the transversal plane of the segments were substantial compared to the longitudinal axis regarding the distal extremity of the tibia, and the lateral epicondyle of the femur. Further, the spectral content was wider at the distal than at the proximal end of the lower-limb. Finally, to get a thorough understanding of the risks incurred by the runners, the need to account for shock-induced vibrations up to 50 Hz has been stressed when investigating three-dimensional vibrations. The overall study raises attention on the substantial importance of the transverse components of the acceleration, and their potential relation to shear fatigue and injury during running

Four degree-of-freedom lumped parameter model of the foot-ankle system exposed to vertical vibration from 10 to 60 Hz with varying centre of pressure conditions

Modelling the foot-ankle system (FAS) while exposed to foot-transmitted vibration (FTV) is essential for designing inhibition methods to prevent the effects of vibration-induced white-foot. K-means analysis was conducted on a data set containing vibration transmissibility from the floor to 24 anatomical locations on the right foot of 21 participants. The K-means analysis found three locations to be sufficient for summarising the FTV response. A three segment, four degrees-of-freedom lumped parameter model of the FAS was designed to model the transmissibility response at three locations when exposed to vertical vibration from 10 to 60 Hz. Reasonable results were found at the ankle, midfoot, and toes in the natural standing position (mean-squared error (ε) = 0.471, 0.089, 0.047) and forward centre of pressure (COP) (ε = 0.539, 0.058, 0.057). However, when the COP is backward, the model does not sufficiently capture the transmissibility response at the ankle (ε = 1.09, 0.219, 0.039).This work was supported by a Natural Science and Engineering Council of Canada Discovery Grant [RGPIN/ 4252-2015]

Development of a two-dimensional dynamic model of the foot-ankle system exposed to vibration

Workers in mining, mills, construction and some types of manufacturing are exposed to vibration that enters the body through the feet. Exposure to foot-transmitted vibration (FTV) is associated with an increased risk of developing vibration-induced white foot (VIWFt). VIWFt is a vascular and neurological condition of the lower limb, leading to blanching in the toes and numbness and tingling in the feet, which can be disabling for the worker. This paper presents a two-dimensional dynamic model describing the response of the foot-ankle system to vibration using four segments and eight Kelvin-Voigt models. The parameters of the model have been obtained by minimizing the quadratic reconstruction error between the experimental and numerical curves of the transmissibility and the apparent mass of participants standing in a neutral position. The average transmissibility at five locations on the foot has been optimized by minimizing the difference between experimental data and the model prediction between 10 and 100 Hz. The same procedure has been repeated to fit the apparent mass measured at the driving point in a frequency range between 2 and 20 Hz. Monte Carlo simulations were used to assess how the variability of the mass, stiffness and damping matrices affect the overall data dispersion. Results showed that the 7 degree-of-freedom model correctly described the transmissibility: the average transmissibility modulus error was 0.1. The error increased when fitting the transmissibility and apparent mass curves: the average modulus error was 0.3. However, the obtained values were reasonable with respect to the average inter-participant variability experimentally estimated at 0.52 for the modulus. Study results can contribute to the development of materials and equipment to attenuate FTV and, consequently, lower the risk of developing VIWFt.INAI

Interaction musicien / instrument : le cas de la harpe de concert

The physics of musical instruments has been studied to a point where many instruments can now be modeled to produce realistic sound synthesis. However, the knowledge of the mechanics of any system is not sufficient to predict its behavior after a human interaction. Thus, the investigation of the musician-instrument interaction is an active field of research, which aims at including the musician impact on the sound production. Eventually, it will be valuable to provide more realistic sound synthesis. Over the years, trained instrumentalists develop the ability to produce notes in a specific and reproducible way. They learn how to control their gestures to perform each note with the desired acoustical features. This thesis studies the control parameters used by the harpist in relation to the produced sound. First, the player/harp interaction has been investigated by characterizing the musical gestures in relation to the musical interpretation. Then, we focused on the gesture directly involved in the sound production, i.e. the plucking action. This analysis had underlined the characteristics of string plucking, both highly reproducible and player-specific. Finally, a previous model of the finger / string interaction has been enhanced by using these results. It has been validated by a repeatable and configurable robotic finger.Dans le domaine de l'acoustique musicale, les recherches visant à la compréhension des instruments ont rendu possible la modélisation et la synthèse sonore de nombre d'entre eux. Cependant, le degré de connaissance acquis d'un système matériel, si élevé soit-il, ne permet pas à lui seul de prédire son comportement à la suite d'une interaction avec l'homme. L'étude de l'interaction entre musicien et instrument fait ainsi l'objet de nombreux travaux de recherche afin de prendre en considération son effet sur la production sonore et d'effectuer, à terme, des synthèses sonores plus réalistes. Au cours de leur apprentissage, les musiciens développent une importante maîtrise de leur instrument de manière à exécuter précisément les gestes nécessaires à la qualité sonore désirée. La mise en évidence des paramètres de contrôle pertinents vis-à-vis du son produit, dans le cas de la harpe de concert, est au centre de ce travail de thèse. Dans un premier temps, cette interaction est étudiée à l'échelle du musicien par le biais d'une analyse de ses gestes instrumentaux et ancillaires en relation avec le contexte et l'intention musicale. La seconde partie de ce travail se focalise sur la cause directe de la production sonore, i.e. le pincement de la corde. La spécificité et l'importante répétabilité de ce geste pour chaque instrumentiste est ainsi mise en évidence. Enfin, une modélisation de l'interaction entre le doigt du musicien et la corde de harpe enrichie des précédents résultats est proposée, validée par l'utilisation d'un doigt artificiel contrôlable et paramétrable

Interaction musicien / instrument (le cas de la harpe de concert)

Dans le domaine de l'acoustique musicale, les recherches visant à la compréhension des instruments ont rendu possible la modélisation et la synthèse sonore de nombre d'entre eux. Cependant, le degré de connaissance acquis d'un système matériel, si élevé soit-il, ne permet pas à lui seul de prédire son comportement à la suite d'une interaction avec l'homme. L'étude de l'interaction entre musicien et instrument fait ainsi l'objet de nombreux travaux de recherche afin de prendre en considération son effet sur la production sonore et d'effectuer, à terme, des synthèses sonores plus réalistes. Au cours de leur apprentissage, les musiciens développent une importante maîtrise de leur instrument de manière à exécuter précisément les gestes nécessaires à la qualité sonore désirée. La mise en évidence des paramètres de contrôle pertinents vis-à-vis du son produit, dans le cas de la harpe de concert, est au centre de ce travail de thèse. Dans un premier temps, cette interaction est étudiée à l'échelle du musicien par le biais d'une analyse de ses gestes instrumentaux et ancillaires en relation avec le contexte et l'intention musicale. La seconde partie de ce travail se focalise sur la cause directe de la production sonore, i.e. le pincement de la corde. La spécificité et l'importante répétabilité de ce geste pour chaque instrumentiste est ainsi mise en évidence. Enfin, une modélisation de l'interaction entre le doigt du musicien et la corde de harpe enrichie des précédents résultats est proposée, validée par l'utilisation d'un doigt artificiel contrôlable et paramétrable.The physics of musical instruments has been studied to a point where many instruments can now be modeled to produce realistic sound synthesis. However, the knowledge of the mechanics of any system is not sufficient to predict its behavior after a human interaction. Thus, the investigation of the musician-instrument interaction is an active field of research, which aims at including the musician impact on the sound production. Eventually, it will be valuable to provide more realistic sound synthesis. Over the years, trained instrumentalists develop the ability to produce notes in a specific and reproducible way. They learn how to control their gestures to perform each note with the desired acoustical features. This thesis studies the control parameters used by the harpist in relation to the produced sound. First, the player/harp interaction has been investigated by characterizing the musical gestures in relation to the musical interpretation. Then, we focused on the gesture directly involved in the sound production, i.e. the plucking action. This analysis had underlined the characteristics of string plucking, both highly reproducible and player-specific. Finally, a previous model of the finger / string interaction has been enhanced by using these results. It has been validated by a repeatable and configurable robotic finger.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

The Effects of Altering the Center of Pressure in Standing Subjects Exposed to Foot-Transmitted Vibration on an Optimized Lumped-Parameter Model of the Foot

Many workers are exposed to foot-transmitted vibration, which can lead to the development of vibration-induced white foot: a debilitating condition with neurological, vascular and osteoarticular symptoms. To design effective prevention mechanisms (i.e., boots and insoles) for isolating workers from vibration exposure, continued model development of the foot’s biodynamic response in different positions is necessary. This study uses a previously developed model of the foot–ankle system (FAS) to investigates how altering the center of pressure (COP) location can change the biodynamic response of the FAS to standing vibration exposure. Formerly published experimental responses for apparent mass and transmissibility at five anatomical locations in three COP positions were used to optimize the model. Differences occurred with the Kelvin–Voigt elements used to represent the soft tissues of the foot sole: at the heel, the distal head of the metatarsals and distal phalanges. The stiffness increased wherever the COP was concentrated (i.e., forward over the toes or backward over the heel). The variability of the model parameters was always greatest when the COP was concentrated in the heel. This suggests future FAS models need to more clearly address how the soft tissue of the plantar fat pad is modelled

A model of harp plucking

In this paper, a model of the harp plucking is developed. It is split into two successive time phases, the sticking and the slipping phases, and uses a mechanical description of the human finger's behavior. The parameters of the model are identified through measurements of the finger/string displacements during the interaction. The validity of the model is verified using a configurable and repeatable robotic finger, enhanced with a silicone layer. A parametric study is performed to investigate the influence of the model's parameters on the free oscillations of the string. As a result, a direct implementation of the model produces an accurate simulation of a string response to a given finger motion, as compared to experimental data. The set of parameters that govern the plucking action is divided into two groups: Parameters controlled by the harpist and parameters intrinsic to the plucking. The former group and to a lesser extent the latter highly influence the initial conditions of the string vibrations. The simulations of the string's free oscillations highlight the large impact the model parameters have on the sound produced and therefore allows the understanding of how different players on the same instrument can produce a specific/personal sound quality

Comportement vibratoire des raquettes et sollicitations du membre supérieur lors de la pratique du padel

Lors de la pratique du padel, les vibrations induites par la frappe de la balle sont directement transmises au membre supérieur. Ces vibrations peuvent être associées à une sensation d’inconfort, augmenter la fatigue musculaire, voire favoriser l’apparition de blessures. Ainsi, la compréhension du comportement dynamique des raquettes de padel est d'un grand intérêt pour la performance mais aussi pour la santé des athlètes. Cette étude vise à identifier les propriétés vibratoires de quatre raquettes de padel ainsi que les sollicitations transmises au membre supérieur en situation de jeu. Pour cela, un système de mesures accélérométriques embarqué a été développé et utilisé afin de mesurer l’accélération en plusieurs points de la raquette, mais aussi au poignet, coude et épaule d’une joueuse. Les paramètres modaux des raquettes ont été identifiés à l’aide d’une analyse modale opérationnelle puis comparés à ceux préalablement obtenus lors d’une analyse modale expérimentale. Les résultats indiquent une légère déviation des fréquences modales ainsi qu’une augmentation de la variabilité des coefficients d’amortissement modaux avec la préhension. Comme attendu, l’énergie des signaux mesurés aux articulations tend à décroître le long du membre supérieur. Enfin, le contenu spectral transmis au poignet varie en fonction de la raquette utilisée, ouvrant des perspectives quant au confort perçu par l’athlète