Segmental vibration transmissibility of seated occupant from lumped parameter models

2011 ◽  
Vol 18 (11) ◽  
pp. 1683-1689 ◽  
Author(s):  
Masilamany Santha Alphin ◽  
Krishnaswamy Sankaranarayanasamy ◽  
Suthangathan Paramashivan Sivapirakasam
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Biomechanical Model ◽  
Dynamic Parameter ◽  
Experimental Results ◽  
Lumped Parameter Model ◽  
Whole Body ◽  
Driving Frequency ◽  
Lumped Parameter ◽  
Lumped Parameter Models

One of the important parameters for the comfort of a seated occupant of a vehicle is the dynamic parameter. The effects of vibration depend on biomechanical characteristics, transmissibility (TR) and apparent mass. The range of input vibration at the seat and TR at the driving frequency will decide the magnitude of the displacement at any point of the human occupant. The most preferred form of biomechanical model for unidirectional whole body vibration is the lumped parameter model. Lumped parameter models are formulated by number of masses depending on the number of degrees-of-freedom (d.f.). The objective of this work is to study the vibration TR by developing the equations of motion (EOM) for different d.f. models for the seated occupant. Then the generated equations of motion for lumped parameter models are solved using the frequency domain technique. In this paper two, four, seven and 11 d.f. models are considered. The TR values are determined by solving the derived parameters using the MATLAB program. The maximum seats to head TR in the case of two, four, seven and 11 d.f. are obtained at the frequency of 2 Hz, 2.5 Hz, 3.15 Hz, and 4 Hz respectively. The TR obtained from models is compared with real time experimental results. The comparison shows a better fit for the TR obtained from the four and seven d.f. models. There is a wide deviation from the TR observed with two and 11 degrees of models when compared with experimental results of the past literature.

An appropriate biomechanical model of seated human subjects exposed to whole-body vibration

2021 ◽  
pp. 146441932110394
Author(s):  
Raj Desai ◽  
Anirban Guha ◽  
Pasumarthy Seshu
Keyword(s):  
Degrees Of Freedom ◽  
Human Subjects ◽  
Computational Cost ◽  
Biomechanical Model ◽  
Whole Body ◽  
Body Parts ◽  
Lumped Parameter ◽  
Long Duration ◽  
The One ◽  
The Right

Long duration automobile-induced vibration is the cause of many ailments to humans. Predicting and mitigating these vibrations through seat requires a good model of seated human body. A good model is the one that strikes the right balance between modelling difficulty and simulation results accuracy. Increasing the number of body parts which have been separately modelled and increasing the number of ways these parts are connected to each other increase the number of degrees of freedom of the entire model. A number of such models have been reported in the literature. These range from simple lumped parameter models with limited accuracy to advanced models with high computational cost. However, a systematic comparison of these models has not been reported till date. This work creates eight such models ranging from 8 to 26 degrees of freedom and tries to identify the model which strikes the right balance between modelling complexity and results accuracy. A comparison of the models’ prediction with experimental data published in the literature allows the identification of a 12 degree of freedom backrest supported model as optimum for modelling complexity and prediction accuracy.

Vibration Modes of Helical Planetary Gears

2009 ◽  
Author(s):  
Tugan Eritenel ◽  
Robert G. Parker
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Rigid Bodies ◽  
Three Dimensions ◽  
Lumped Parameter Model ◽  
Vibration Modes ◽  
Planetary Gears ◽  
Gear Mesh ◽  
Modal Properties ◽  
Lumped Parameter

This paper examines the vibration modes of single stage helical planetary gears in three dimensions with equally spaced planets. A lumped-parameter model is formulated to obtain the equations of motion. The gears and shafts are modeled as rigid bodies with compliant bearings at arbitrary axial locations on the shafts. A translational and a tilting stiffness account for the force and moment transmission at the gear mesh interface. The modal properties generalize those of two-dimensional spur planetary gears; there are twice as many degrees of freedom and natural frequencies due to the added tilting and axial motion. All vibration modes are categorized as planet, rotational-axial, and translational-tilting modes. The modal properties are shown to hold even for configurations that are not symmetric about the gear plane, due to, for example, shaft bearings not being equidistant from the gear plane. Computational modal analysis are performed to numerically verify the findings.

scholarly journals Theoretical Analysis and Optimization of a Gloved Hand-arm System

2021 ◽  
Author(s):  
Oreoluwa Alabi ◽  
Sunit Kumar Gupta ◽  
Oumar Barry
Keyword(s):  
Harmonic Balance ◽  
Equations Of Motion ◽  
Biomechanical Model ◽  
Lumped Parameter Model ◽  
Human Hand ◽  
Governing Equations ◽  
Lumped Parameter ◽  
Hand Tool ◽  
Modeling Techniques ◽  
Linear Spring

Abstract Studies have shown that isolators in the form of anti-vibration gloves effectively reduce the transmission of unwanted vibration from vibrating equipment to the human hand. However, as most of these studies are based on experimental or modeling techniques, the level of effectiveness and optimum glove properties for better performance remains unclear. To fill this gap, hand-arm system dynamics with and without gloves are studied analytically in this work. In the current work, we use a lumped parameter model of the hand-arm system, with hand-tool interaction modeled as a linear spring-damper system. The resulting governing equations of motion are solved analytically using the method of harmonic balance. Parametric analysisis performed on the biomechanical model of the hand-armsystem with and without a glove to identify key design pa-rameters. It is observed that the effect of glove parameters on its performance is not repetitive and changes in the studied different frequency ranges. This observation further motivates us to optimize the glove parameters to minimize the overall transmissibility in different frequency ranges.

scholarly journals Experimental Characterization of the Electrostatic Levitation Force in MEMS Transducers

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Meysam Daeichin ◽  
Ronald N. Miles ◽  
Shahrzad Towfighian
Keyword(s):  
Degrees Of Freedom ◽  
Levitation Force ◽  
Electrostatic Force ◽  
Experimental Results ◽  
Lumped Parameter Model ◽  
Electrostatic Levitation ◽  
Experimental Procedure ◽  
Lumped Parameter ◽  
Micro Electromechanical System

Abstract In this study, a two-step experimental procedure is described to determine the electrostatic levitation force in micro-electromechanical system transducers. In these two steps, the microstructure is excited quasi-statically and dynamically and its response is used to derive the electrostatic force. The experimental results are obtained for a 1 mm by 1 mm plate that employs 112 levitation units. The experimentally obtained force is used in a lumped parameter model to find the microstructure response when it is subjected to different dynamical loads. The natural frequency and the damping ratios in the model are identified from the experimental results. The results show that this procedure can be used as a method to extract the electrostatic force as a function of the microstructure’s degrees-of-freedom. The procedure can be easily used for any microstructure with a wide variety of electrode configurations to predict the response of the system to any input excitation.

A Critical Examination of the Hysteresis in Wells Turbines Using CFD and Lumped Parameter Models

2019 ◽  
Author(s):  
T. Ghisu ◽  
F. Cambuli ◽  
P. Puddu ◽  
I. Virdis ◽  
M. Carta ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Unsteady Aerodynamics ◽  
Lumped Parameter Model ◽  
Hysteretic Behavior ◽  
Critical Examination ◽  
Wells Turbine ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Acceleration And Deceleration ◽  
The Common

Abstract The hysteretic behavior of OWC-installed Wells turbines has been known for decades. The common explanation invokes the presence of unsteady aerodynamics due to the continuously varying incidence of the flow on the turbine blades. This phenomenon is neither new nor unique to Wells turbines, as an aerodynamic hysteresis is present in rapidly oscillating airfoils and wings, as well as in different types of turbomachinery, such as wind turbines and helicopter rotors, which share significant similarities with a Wells turbine. An important difference is the non-dimensional frequency: the hysteresis appears in oscillating airfoils only at frequencies orders of magnitude larger than the ones Wells turbines operate at. This work contains a reexamination of the phenomenon, using both CFD and a lumped parameter model, and shows how the aerodynamic hysteresis in Wells turbines is negligible, and how the often measured differences in performance between acceleration and deceleration are caused by the capacitive behavior of the OWC system.

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].

Highly Reduced Lumped Parameter Models Representing Impedance Functions at the Interface of One-Dimensional Viscoelastic Continua

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Masato Saitoh
Keyword(s):  
Degrees Of Freedom ◽  
Reaction Force ◽  
Lumped Parameter Model ◽  
Computational Time ◽  
Dynamic Problems ◽  
Modal Expansion ◽  
Mass Element ◽  
Lumped Parameter ◽  
In Series ◽  
Impedance Functions

In recent dynamic problems dealing with high-frequency excitations, such as ultrasonic vibrations, a proper representation of rods transmitting kinetic energy from the interface attached to the vibrating system to the other end is strongly demanded for effectively reducing computational time and domain. A highly reduced lumped parameter model that properly simulates the dynamic characteristics of a uniform, isotropic, homogeneous, and viscoelastic rod subjected to excitations at its end is proposed in this paper. The model consists of springs, dashpots, and so called “gyro-mass elements.” The gyro-mass element generates a reaction force proportional to the relative acceleration of the nodes between which it is placed. This model consists of units arranged in series, each unit consisting of a spring, a dashpot, and a gyro-mass element arranged in parallel. A formula is proposed for determining the properties of the elements in the units based on the modal expansion. The results show that a notable reduction of 90% in the degrees of freedom is accomplished with high accuracy by using the proposed model consisting of a set of units associated with modes in a target frequency region and a supplemental unit associated with residual stiffness, which is advantageous for efficient numerical computations in recent dynamic problems.

Characterization of pulmonary arterial input impedance with lumped parameter models

1987 ◽  
Vol 252 (3) ◽  
pp. H585-H593 ◽  
Author(s):  
B. J. Grant ◽  
L. J. Paradowski
Keyword(s):  
Input Impedance ◽  
Goodness Of Fit ◽  
Arterial Compliance ◽  
Characteristic Impedance ◽  
Lumped Parameter Model ◽  
Pulmonary Vasculature ◽  
Impedance Spectra ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Pulmonary Arterial

The purpose of this study is to evaluate systematically the ability of lumped parameter models to approximate pulmonary arterial input impedance (Zin) and estimate characteristic impedance (Zc) and pulmonary arterial compliance (Cart). To assess goodness of fit, the parameters of each model were adjusted so that the model's impedance approximates the Zin measured in anesthetized cats. To assess the ability of the model to estimate Zc and Cart, the lumped parameter models were fitted to Zin calculated from a distributed parameter model of the feline pulmonary vasculature. In addition, we assessed the concordance between the lumped parameter model estimates of Zc and Cart. The results indicate that no one model was superior; any of four models would be a reasonable choice. A four-element model was used to compare Zin measured at different phases of the respiratory cycle. Small differences in the impedance spectra were found that have not been previously reported. We conclude that lumped parameter models can be used to provide close approximations to Zin, to estimate Zc and Cart, and to provide a useful approach for statistical comparisons of impedance spectra.

scholarly journals Modelling of propeller shaft dynamics at pulse load

2008 ◽  
Vol 15 (4) ◽  
pp. 52-58 ◽  
Author(s):  
Andrzej Grządziela
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Model Identification ◽  
Experimental Results ◽  
Real Object ◽  
Pulse Load ◽  
Propeller Shaft ◽  
Matlab Simulink ◽  
External Agents ◽  
Time Histories

Modelling of propeller shaft dynamics at pulse load The article discusses a method of modelling of propeller shaft dynamics at the presence of virtually introduced underwater detonation effects. The propeller shaft model has four degrees of freedom, which provides opportunities for introducing shaft displacements and rotations similar to those observed in a real object. The equations of motion, taking into account the action of external agents, were implemented to the Matlab SIMULINK environment. The obtained time-histories and their spectra were compared with the experimental results of the tests performed on the marine testing ground. The performed model identification confirmed its sensitivity to changing parameters of motion and external actions.

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.

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