Modeling of the Seated Human Body in a Vibrational Medium

2014 ◽  
Vol 658 ◽  
pp. 401-406 ◽  
Author(s):  
Daniela Mariana Barbu
Keyword(s):  
Human Body ◽  
Degrees Of Freedom ◽  
Dynamic Environment ◽  
The Body ◽  
Lumped Parameter Model ◽  
Vibration Effect ◽  
Mechanical Oscillations ◽  
Lumped Parameter ◽  
Irregular Period ◽  
Multi Body

Vibrations are mechanical oscillations produced by regular or irregular period movements of a member or body about its rest position. Vibration can affect visual perception, muscles, concentration, circulation and the respiratory system and at certain levels can even result in physical harm to the body. The effect of vibration on the human body is related to the natural frequency of parts of the human body affected. This paper studies the dynamic characteristics of a seated human body system in a vibration environment. The main result is a multi degrees of freedom lumped parameter model. The model provided an analytical tool for human body dynamics research. It also enabled a primary tool for seat and cushioning design. 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. The relative displacements of human parts are evaluated, which can be a basis for the assessment of vibration risk. It is suggested that the multi-body dynamic model is used to evaluate the vibration effect to the seated subjects.

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.

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.

Identification and Experimental Validation of Damping Ratios of Different Human Body Segments Through Anthropometric Vibratory Model in Standing Posture

2006 ◽  
Vol 129 (4) ◽  
pp. 566-574 ◽  
Author(s):  
T. C. Gupta
Keyword(s):  
Human Body ◽  
Damping Ratio ◽  
Physical Structure ◽  
The Body ◽  
Anthropometric Data ◽  
Body Segments ◽  
Lumped Parameter ◽  
Mass Damper ◽  
Linear Spring ◽  
Experimental Response

A 15degrees of freedom lumped parameter vibratory model of human body is developed, for vertical mode vibrations, using anthropometric data of the 50th percentile US male. The mass and stiffness of various segments are determined from the elastic modulii of bones and tissues and from the anthropometric data available, assuming the shape of all the segments is ellipsoidal. The damping ratio of each segment is estimated on the basis of the physical structure of the body in a particular posture. Damping constants of various segments are calculated from these damping ratios. The human body is modeled as a linear spring-mass-damper system. The optimal values of the damping ratios of the body segments are estimated, for the 15degrees of freedom model of the 50th percentile US male, by comparing the response of the model with the experimental response. Formulating a similar vibratory model of the 50th percentile Indian male and comparing the frequency response of the model with the experimental response of the same group of subjects validate the modeling procedure. A range of damping ratios has been considered to develop a vibratory model, which can predict the vertical harmonic response of the human body.

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.

Mitigation of Biodynamic Response to Shock Loads Using Semi-Active Vertically Stroking Crew Seats

2010 ◽  
Author(s):  
Harinder J. Singh ◽  
Norman M. Wereley
Keyword(s):  
Human Body ◽  
Control Algorithm ◽  
Equations Of Motion ◽  
Comprehensive Analysis ◽  
Lumped Parameter Model ◽  
Force Model ◽  
Body Parts ◽  
Governing Equations ◽  
Lumped Parameter ◽  
Yield Force

This study addresses mitigation of biodynamic response due to an initial velocity impact of a vertically stroking crew seat using an adaptive magnetorheological energy absorber. Under consideration is a multiple degree-of-freedom detailed lumped parameter model of a human body falling with prescribed initial crash velocity (sink rate). The lumped parameter model of the human body consisted of four main parts: pelvis, upper torso, viscera and head. The governing equations of motion of a vertically stroking crew seat incorporating a human body were derived using parameters such as available damper stroke as well as MR yield force. The control algorithm for smooth landing of a rigid occupant was examined for compliant occupant and was modified accordingly. Four MR yield force models were analyzed to shape decelerations experienced by human body and an appropriate model was selected for comprehensive analysis. The simulated responses were analyzed with selected MR yield force model for a crew seat with an occupant corresponding to 90th percentile male at sink rates varying from 8 to 12 m/s. In addition, the mitigation of injuries to the human body parts due to load transmissions corresponding to crash velocities was also evaluated for the selected MR yield force model along with terminal conditions necessary for smooth landing.

Transient Behavior of Seated Human Body During Input From Caudophalad Acceleration

2000 ◽  
Author(s):  
Paul C. Lam ◽  
P. Ruby Mawasha ◽  
Ted Conway
Keyword(s):  
Human Body ◽  
High Speed ◽  
Transient Behavior ◽  
Lumped Parameter Model ◽  
Load Factor ◽  
Time Duration ◽  
Bodily Injury ◽  
Lumped Parameter ◽  
Ejection Process ◽  
Short Time

Abstract The objective of this study, is to investigate the dynamic transient response of a four degree-of-freedom lumped parameter model of the seated human body subjected to caudocephalad loading (acceleration from tail to head). The caudocephalad loading used in the model simulated the ejection process of a seated pilot from a high-speed aircraft. During ejection, ejection velocities are high and are developed over short distances hence, the accelerations are also high (10–40 g’s). The model indicates that even though acceleration is applied over short time duration (typically less than 0.25 seconds), serious bodily injury can result due to high dynamic load factor for the frequency range of body resonances.

Real-Time Motion Capture for a Human Body using Accelerometers

Robotica ◽  
2001 ◽  
Vol 19 (6) ◽  
pp. 601-610 ◽  
Author(s):  
Jihong Lee ◽  
Insoo Ha
Keyword(s):  
Real Time ◽  
Motion Capture ◽  
Human Body ◽  
Degrees Of Freedom ◽  
Low Cost ◽  
Human Motion ◽  
The Body ◽  
Sensor Data ◽  
Time Motion ◽  
Gravity Acceleration

In this paper we propose a set of techniques for a real-time motion capture of a human body. The proposed motion capture system is based on low cost accelerometers, and is capable of identifying the body configuration by extracting gravity-related terms from the sensor data. One sensor unit is composed of 3 accelerometers arranged orthogonally to each other, and is capable of identifying 2 rotating angles of joints with 2 degrees of freedom. A geometric fusion technique is applied to cope with the uncertainty of sensor data. A practical calibration technique is also proposed to handle errors in aligning the sensing axis to the coordination axis. In the case where motion acceleration is not negligible compared with gravity acceleration, a compensation technique to extract gravity acceleration from the sensor data is proposed. Experimental results not only for individual techniques but also for human motion capturing with graphics are included.

A BIOMECHANICAL MODEL AS A SEATED HUMAN BODY FOR CALCULATION OF VERTICAL VIBRATION TRANSMISSIBILITY USING A GENETIC ALGORITHM

2013 ◽  
Vol 13 (04) ◽  
pp. 1350053 ◽  
Author(s):  
JAVAD MARZBANRAD ◽  
AMIR AFKAR
Keyword(s):  
Genetic Algorithm ◽  
Human Body ◽  
Coupled Model ◽  
Whole Body ◽  
Biomechanical Models ◽  
Mean Error ◽  
Lumped Parameter ◽  
Vertical Vibrations ◽  
Stiffness And Damping ◽  
Multi Body

Many biomechanical models of whole body vibrations have been developed, as part of the design, optimization, and vibrations control of vehicle seat systems, with the aim of achieving greater comfort. Most of these models are complex and result in large errors. In this paper, we introduce two new models, with and without backrest support, within a specific frequency domain. One is an optimized seven-degrees-of-freedom (7-DoF) lumped-parameter model with a unique structure to display vertical vibrations in one direction. The other is a new type of model called the coupled model, where the stiffness and damping matrices are employed instead of the spring and damper scalar parameters to present vertical vibrations in two directions — vertical and horizontal. The use of matrices not only simplifies and reduces DoF, but also gives more accurate results in comparison with the conventional multi-body models. With the help of a genetic algorithm (GA) through the global criterion method, we obtained numerical parameters of both models including mass, stiffness, and damping, which minimized the errors. The mean error for the 7-DoF model was 2.2%, while the best lumped-parameter models previously developed produced 12.6%. For the coupled model, we measured a mean error of 7%, a significant improvement over a well-known multi-body model with a mean error of 22.4%. Finally, we compared the transmissibility of vibrations in the human body applying the two models in the frequency range below 6 Hz, in both cases of with and without a backrest. These confirmed the importance of the backrest.

Analytical Evaluation of Adaptive Seat Energy Absorber for Rotorcraft Semi-Active Crash Safety Seat Development

2013 ◽  
Author(s):  
Muthuvel Murugan ◽  
JinHyeong Yoo ◽  
Gregory Hiemenz ◽  
Norman Wereley
Keyword(s):  
Human Body ◽  
Simulation Software ◽  
Dynamics Simulation ◽  
Crash Severity ◽  
Analytical Evaluation ◽  
Severity Level ◽  
Occupant Protection ◽  
Body Regions ◽  
Lumped Parameter ◽  
Multi Body

This research study focuses on the analytical evaluation of magneto-rheological (MR) dampers for enhanced occupant protection during vertical crash landings of a helicopter. The current state-of-the-art helicopter crew seat has passive safety mechanisms that are highly limited in their capability to optimally adapt to each type of crash scenario due to variations in both occupant weight and crash severity level. While passive crash energy absorbers work well for a single design condition (50th percentile male occupant and fixed crash severity level), they do not offer adequate protection across a broad spectrum of crash conditions by minimizing the load transmitted to the occupant. This study reports the development of a lumped-parameter human body model including lower leg in a seated posture for rotorcraft crash injury simulation. A physical model of lumped-parameter human body restrained on a crew seat was implemented in multi-body dynamics simulation software. For implementing control, a control algorithm was made to work with the multi-body dynamic model by running co-simulation. The injury criteria and tolerance levels for the biomechanical effects are discussed for each of the identified vulnerable body regions, such as the thoracic lumbar loads for different sized adults. The desired objective of this analytical model development is to develop a tool to study the performance of adaptive semi-active magnetorheological seat suspensions for rotorcraft occupant protection.

Analysis and Design of Cam-Driven Mechanisms With Nonlinearities

1973 ◽  
Vol 95 (3) ◽  
pp. 685-694 ◽  
Author(s):  
F. Y. Chen
Keyword(s):  
Computer Aided Design ◽  
Degrees Of Freedom ◽  
Lumped Parameter Model ◽  
Analysis Tool ◽  
Analysis And Design ◽  
Lumped Parameter ◽  
Method Of Solution ◽  
Parametric Studies ◽  
Rational Procedure ◽  
Aided Design

The cam-and-follower mechanism is represented by a lumped parameter model of finite degrees of freedom, in which nonlinear system parameters may be taken into account. An approximate dynamic analysis of the system excited by either functional or numerical form of the base motion of a cam is obtained. The method of solution which uses an interpolating polynomial for approximating the excitation function and mechanical quadrature for evaluating the convolution integral is well suited for computer programming. A digital computer program for analysis based on this scheme is developed. In order to utilize the analysis tool for design purposes, parametric studies are conducted, design stratagems are presented and a rational procedure of closed loop computer-aided design is outlined and discussed.

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