scholarly journals 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

Vibration ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 893-905
Author(s):  
Stefano Marelli ◽  
Delphine Chadefaux ◽  
Katie Goggins ◽  
Tammy Eger ◽  
Diego Scaccabarozzi ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Center Of Pressure ◽  
Model Development ◽  
Lumped Parameter Model ◽  
Model Parameters ◽  
Vibration Exposure ◽  
Apparent Mass ◽  
Fat Pad ◽  
Effective Prevention ◽  
Lumped Parameter

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.

Modeling the Human Body/Seat System in a Vibration Environment

2003 ◽  
Vol 125 (2) ◽  
pp. 223-231 ◽  
Author(s):  
Jacob Rosen ◽  
Mircea Arcan
Keyword(s):  
Human Body ◽  
Muscle Tension ◽  
Design Guidelines ◽  
Contact Forces ◽  
Lumped Parameter Model ◽  
Model Parameters ◽  
Apparent Mass ◽  
Human Dynamics ◽  
Lumped Parameter ◽  
Body Dynamics

The vibration environment is a common man-made artificial surrounding with which humans have a limited tolerance to cope due to their body dynamics. This research studied the dynamic characteristics of a seated human body/seat system in a vibration environment. The main result is a multi degrees of freedom lumped parameter model that synthesizes two basic dynamics: (i) global human dynamics, the apparent mass phenomenon, including a systematic set of the model parameters for simulating various conditions like body posture, backrest, footrest, muscle tension, and vibration directions, and (ii) the local human dynamics, represented by the human pelvis/vibrating seat contact, using a cushioning interface. The model and its selected parameters successfully described the main effects of the apparent mass phenomenon compared to experimental data documented in the literature. The model provided an analytical tool for human body dynamics research. It also enabled a primary tool for seat and cushioning design. The model was further used to develop design guidelines for a composite cushion using the principle of quasi-uniform body/seat contact force distribution. In terms of evenly distributing the contact forces, the best result for the different materials and cushion geometries simulated in the current study was achieved using a two layer shaped geometry cushion built from three materials. Combining the geometry and the mechanical characteristics of a structure under large deformation into a lumped parameter model enables successful analysis of the human/seat interface system and provides practical results for body protection in dynamic environment.

A Three Degree of Freedom Lumped Parameter Model of Whole Body Vibration Along the Spine in the Rat

2013 ◽  
Author(s):  
Nicolas V. Jaumard ◽  
Hassam A. Baig ◽  
Benjamin B. Guarino ◽  
Beth A. Winkelstein
Keyword(s):  
Whole Body Vibration ◽  
Degree Of Freedom ◽  
Lumped Parameter Model ◽  
In Vivo Studies ◽  
Whole Body ◽  
Model Parameters ◽  
Body Vibration ◽  
Lumped Parameter ◽  
Three Degree Of Freedom

Whole body vibration (WBV) can induce a host of pathologies, including muscle fatigue and neck and low back pain [1,2]. A new model of WBV in the rat has been developed to define relationships between WBV exposures, kinematics, and behavioral sensitivity (i.e. pain) [3]. Although in vivo studies provide valuable associations between biomechanics and physiology, they are not able to fully define the mechanical loading of specific spinal regions and/or the tissues that may undergo injurious loading or deformation. Mathematical models of seated humans and primates have been used to estimate spinal loads and design measures that mitigate them during WBV [4–6]. Although such models provide estimates of relative spinal motions, they have limited utility for relating potentially pathological effects of vibration-induced kinematics and kinetics since those models do not enable simultaneous evaluation of relevant spinal tissues with the potential for injury and pain generation. As such, the goal of this work was to develop and validate a three degree of freedom (3DOF) lumped-parameter model of the prone rat undergoing WBV directed along the long-axis of the spine. The model was constructed with dimensions of a generalized rat and model parameters optimized using kinematics over a range of frequencies. It was validated by comparing predicted and measured transmissibility and further used to predict spinal extension and compression, as well as acceleration, during WBV for frequencies known to produce resonance in the seated human and pain in the rat [3,7].

scholarly journals Mathematical Model of Suspension Seat-Person Exposed to Vertical Vibration for Off-Road Vehicles

2019 ◽  
Vol 16 (2) ◽  
pp. 6773-6782
Author(s):  
S. Aisyah Adam ◽  
N. A. A. Jalil ◽  
K. A. Md Razali ◽  
Y. G. Ng ◽  
M. F. Aladdin
Keyword(s):  
Human Body ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Coupled System ◽  
Vertical Vibration ◽  
Lumped Parameter Model ◽  
Model Parameters ◽  
Road Vehicles ◽  
Lumped Parameter ◽  
Variable Function

Off-road drivers are exposed to a high magnitude of vibration at low frequency (0.5-25Hz), that can cause harm and possibly attribute to musculoskeletal disorder, particularly low-back pain. The suspension seat is commonly used on an off-road condition to isolate the vibration transmitted to the human body. Nevertheless, the suspension seat modelling that incorporates the human body is still scarce. The objective of this study is to develop a mathematical modelling to represent the suspension seat-person for off-road vehicles. This paper presents a three degrees-of-freedom lumped parameter model. A curve-fitting method is used for parameter identification, which includes the constraint variable function (fmincon()) from the optimisation toolbox of MATLAB(R2017a). The model parameters are optimised using experimentally measured of suspension seat transmissibility. It was found that the model provides a reasonable fit to the measured suspension seat transmissibility at the first peak of resonance frequency, around 2-3 Hz. The results of the study suggested that the human body forms a coupled system with the suspension seat and thus affects the overall performance of the suspension system.  As a conclusion, the influence of the human body should not be ignored in the modelling, and a three-degrees degree-of-freedom lumped parameter model provides a better prediction of suspension seat transmissibility. This proposed model is recommended to predict vibration transmissibility for off-road suspension seat.

Modeling and Parameter Estimation of Robot Manipulators Using Extended Flexible Joint Models

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Stig Moberg ◽  
Erik Wernholt ◽  
Sven Hanssen ◽  
Torgny Brogårdh
Keyword(s):  
Parameter Estimation ◽  
Robot Manipulators ◽  
Joint Model ◽  
Lumped Parameter Model ◽  
Model Parameters ◽  
Joint Models ◽  
Model Accuracy ◽  
Flexible Joint ◽  
Industrial Manipulator ◽  
Lumped Parameter

This paper considers the problem of dynamic modeling and identification of robot manipulators with respect to their elasticities. The so-called flexible joint model, modeling only the torsional gearbox elasticity, is shown to be insufficient for modeling a modern industrial manipulator accurately. Another lumped parameter model, called the extended flexible joint model, is therefore used to improve the model accuracy. In this model, nonactuated joints are added to model the elasticity of the links and bearings. The unknown elasticity parameters are estimated using a frequency-domain gray-box identification method. The conclusion is that the obtained model describes the movements of the motors and the tool mounted on the robot with significantly higher accuracy than the flexible joint model. Similar elasticity model parameters are obtained when using two different output variables for the identification, the motor position and the tool acceleration.

Evaluation of the Human Body Equilibrium in a Vibration Environment

2015 ◽  
Vol 801 ◽  
pp. 295-299
Author(s):  
Daniela Mariana Barbu ◽  
Mihaela Ioana Baritz
Keyword(s):  
Human Body ◽  
Degrees Of Freedom ◽  
Soft Tissues ◽  
Lumped Parameter Model ◽  
Internal Organs ◽  
Vibratory System ◽  
Lumped Parameter ◽  
Body Dynamics ◽  
Human Balance ◽  
External Sources

In the human body, vibrations are generated by internal or external sources. Because of the soft tissues, bones, joints, internal organs and also because of its anatomical particularities components in general, the human body is a complex vibratory system. The vibrations from external sources can be transmitted to the human body when it is positioned in different manners: standing, sitting, recumbent and moving or at work. The effect of vibration on the human body is related to the natural frequency of affected parts in the human body. This paper studies the dynamic characteristics of a human body system in a vibration environment and sets limits to which the balance is affected. The main result is a multi degrees of freedom lumped parameter model. The model provides an analytical tool for human body dynamics research. The relative displacements of human parts are evaluated, which can be a basis for the assessment of vibration risk and setting limits for keeping human balance.

scholarly journals Lumped parameter modelling and methodology for extraction of model parameters for an electrodynamic shaker

2017 ◽  
Vol 36 (2) ◽  
pp. 99-115 ◽  
Author(s):  
Nachiketa Tiwari ◽  
Amrita Puri ◽  
Abhishek Saraswat
Keyword(s):  
Transfer Functions ◽  
Academic Research ◽  
Parameter Extraction ◽  
Lumped Parameter Model ◽  
Model Parameters ◽  
Mechanical Parameters ◽  
Lumped Parameter ◽  
Different Types ◽  
Electrodynamic Shaker ◽  
Non Destructive

Shakers are widely used to simulate the vibrations for academic research, as well as for product testing. Thus, there is a significant necessity to study them in detail. Amongst the different types of shakers being used, the electrodynamic shaker is by far the most versatile. However, limited work has been done with regard to their integrated electro-mechanical modelling. In this work, we have developed a mobility-based lumped parameter model of an electrodynamic shaker and also a method to measure its various electrical and mechanical parameters using non-destructive and easy to use methods. Towards meeting the latter goal, we conducted experiments to determine the shaker table’s impedance and transfer functions, and used these data for subsequent parameter extraction. Such a model was later validated experimentally. Finally, we predicted the response of the shaker under loaded and unloaded conditions, and confirmed their validity through actual experimental data.

Method for Lumped Parameter Simulation of Digital Displacement Pumps/Motors Based on CFD

2013 ◽  
Vol 397-400 ◽  
pp. 615-620 ◽  
Author(s):  
Daniel Beck Roemer ◽  
Per Johansen ◽  
Henrik C. Pedersen ◽  
Torben O. Andersen
Keyword(s):  
Computational Cost ◽  
Simulation Models ◽  
Lumped Parameter Model ◽  
Model Parameters ◽  
Lumped Parameter ◽  
Displacement Pump ◽  
Variable Displacement ◽  
And Performance ◽  
And Control ◽  
Low Computational Cost

Digital displacement fluid power pumps/motors offers improved efficiency and performance compared to traditional variable displacement pump/motors. These improvements are made possible by using efficient electronically controlled seat valves and careful design of the flow geometry. To optimize the design and control of digital displacement machines, there is a need for simulation models, preferably models with low computational cost. Therefore, a low computational cost generic lumped parameter model of digital displacement machine is presented, including a method for determining the needed model parameters based on steady CFD results, in order to take detailed geometry information into account. The response of the lumped parameter model is compared to a computational expensive transient CFD model for an example geometry.

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