Absorbed power distribution in the whole-body system of a tractor operator.
OBJECTIVE
Many people are exposed to vibration (WBV) in their occupational lives. The biodynamic responses of the human body in sitting conditions have been widely measured under whole-body vibration (WBV). The measures are most often expressed in terms of force-motion relations at the driving-point, namely, mechanical impedance, apparent mass and absorbed power, and flow of vibration through the body, such as seat-to-head and body segments vibration transmissibility. The absorbed power is a measure of the energy absorbed by the subject due to the external forces applied to the system.


METHODS
The body behaves like a vibrating physical system with distributed energy-storage elements (masses, springs) and energy-dissipation elements (dampers). The total quantity of power can be divided into 2 components - one real and one imaginary. The real component reflects the energy-absorbing part of the system, due to the transformation of friction into heat within the tissues. The imaginary component reflects the energy-storing part of the system which does not consume any vibration energy.


RESULTS
The seated human is modeled as a series 4-DOF dynamic models. After introduction of the excitation, the response in particular segments of the model can be analyzed. As an example, the vibration power dissipated in an operator's body segments has been determined as a function of the agricultural combination operating speed 1.4 - 2.75 ms(-1).


CONCLUSIONS
The concept of absorbed power as a measurement for evaluation of WBV exposure opens a new area for research. The important character of absorbed power is that it has physical significance and therefore can be measured as well as computed analytically. The absorbed power relates to dissipation of energy attributed to relative motions of the visco-elastic tissues, muscles and skeletal system, which under prolonged exposures could lead to physical damage in the musculoskeletal system. A structural model of the human operator allows determination of the dynamic characteristics of the model, and study of the energy flow between the elements of the model.
Industrial Institute of Agricultural Engineering, Poznań, Poland.
Jacek
J
Kromulski
Industrial Institute of Agricultural Engineering, Poznań, Poland.
Tadeusz
T
Pawłowski
Industrial Institute of Agricultural Engineering, Poznań, Poland.
Jan
J
Szczepaniak
University of Life Sciences, Lublin, Poland.
Wojciech
W
Tanaś
Department of Health Sciences, University of Medical Sciences, Poznań, Poland.
Andrzej
A
Wojtyła
University of Life Sciences, Lublin, Poland.
Mariusz
M
Szymanek
University of Technology, Lublin, Poland.
Jacek
J
Tanaś
Warsaw University of Technology, Poland.
Waldemar
W
Izdebski
D000383:Agriculture / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D006801:Humans; D008962:Models, Theoretical; D016273:Occupational Exposure; D014732:Vibration