• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.218-223
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• 2011

Seated human subjects have been exposed to vertical vibration so as to investigate six-axis biodynamic response. Sixteen males were exposed to random vertical vibration in the frequency range(3~40Hz) at one vibration magnitude(0.224m/$s^2$ r.m.s.). Forces were measured in the vertical, fore-and-aft, lateral, roll, pitch and yaw direction on the seat. The median of cross-axis apparent mass magnitude in the fore-and-aft direction could reach up to 20% of the apparent mass magnitude at resonance frequency. And the median of apparent eccentric mass magnitude in the roll direction could reach up to 15% of the apparent eccentric mass magnitude in the pitch direction at resonance frequency. But cross-axis apparent mass in the lateral direction and apparent eccentric mass in the yaw direction showed very small.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.8
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• pp.645-650
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• 2003

This paper introduces attempts to obtain the 'representative'characteristics of the apparent mass (or dynamic mass) of seated Korean subjects under vertical vibration. Individual responses of driving-oint apparent masses obtained from forty one Korean subjects are illustrated. Four kinds of vibration levels and three different sitting postures are selected to collect the characteristic responses of each subject. Those individual responses are used to estimate the 'mean'apparent mass, which may be expected to be a representative model to Korean subjects. Several interesting features of the estimated apparent mass are suggested and compared to those of ISO 5982.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.897-904
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• 2011

When whole-body is exposed to vertical vibration, asymmetry shape of human body affects the response on the translational(fore-aft, lateral, vertical) and rotational(roll, pitch, yaw) motion. While the translational motion has been studied with various titles, it has been rare to study the rotational motion of human body exposed to vertical excitation because of lack of experimental equipment. This study was performed by using a 6-axis force plate installing strain gage type sensors for the rotational response. Sixteen male subjects were exposed to vertical vibration on rigid seat in order to investigate apparent mass of three translational motion and apparent eccentric mass of three rotational motion. Random signal was generated to make excitation vibration which was on an effective frequency range of 3~40 Hz, and magnitude of 0.224 m/$s^2$ r.m.s. The frequency range and magnitude used was selected for the vibration of passenger vehicle on idling condition. As the result, cross-axis apparent masses of fore-and-aft and lateral direction were not significant showing 20 % and 3 % of vertical apparent mass relatively. And apparent eccentric mass of pitch motion was dominant when compared to that of roll and yaw motion, which is reasoned by asymmetry direction of human body sitting on a seat.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1121-1127
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• 2010

Human characteristic responding to idle vibration on passenger vehicle was studied to find if affected by seating posture of passenger. When twelve male subjects are exposed to moderate vertical vibration of 0.224 $m/s^2$ r.m.s. at frequency range from 3 Hz to 40 Hz, it was found that seating posture significantly affects to biodynamical characteristics, apparent mass and apparent eccentric mass, at most range of idle vibration frequency(20~40 Hz). The supported thigh contact on rigid seat showed bigger values in the two biodynamical characteristics than the average thigh contact. The bigger apparent mass and apparent eccentric mass in the seating posture of the supported thigh contact can be assumed more strengthened muscle at the frequency range.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.241-245
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• 2003

When considering the effects of whole-body vertical vibration, it is valuable to have an understanding of the mechanical characteristics (mechanical impedance and apparent mass) of the body. This paper addresses experimental results carried out to investigate the characteristics of apparent masses fer 41 Korean. The apparent masses of the seated human body in vertical direction were measured during different experimental conditions, such as vibration excitation level (0.5-2 ms$\^$-2/ r.m.s). frequency range (1-50Hz), and upper body posture (relaxed, normal and backrest-upright). We showed the average of all subjects and all conditions and compared the results with ISO5982/DIS (2000).

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.148.2-148
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• 2001

The most important difference of an airship from conventional vehicle is that it has the apparent mass and inertia provided from the existence of Helium gas inside the airship. To acquire To acquire the exact response of the airship, the longitudinal responses of airship with respect to the vertical gust, which is the non-linear system, have been studied. An Airship has neutral buoyancy in equilibrium state. When it moves, its motion shows much difference comparing with conventional aircraft. Here, we compare two cases, the one has the apparent mass and the other hasn´t. With the apparent mass, the magnitude of the former response is smaller than the latter, while the frequency is higher. However, the apparent mass delay ...

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.522-528
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• 2000

Dynamic characteristics of seated human body were investigated by measuring apparent masses of eight different seating subjects exposed to vertical vibration. Two types of vibration signals - one is random signals over 1 to 30Hz having flat spectral density and the other is signals measured on seat rail in passenger car under driving conditions - were employed. It was found that the apparent masses are highly dependent on vibration level rather than type of the vibration signals. Based on the apparent mass measurements, a mathematical model of the human body in seating posture was developed by using genetic algorithm. Three-degree-of-freedom model was satisfactory in describing apparent mass of seated human body.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.369-374
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• 2004

This study aims to measure an apparent mass of a seated human body at the sitting posture in a passenger car in the frequency range from 1 to 20 Hz and to investigate the dynamic characteristics. Thirty subjects joined the test where eight levels of acceleration from $0.1m/s^2\;to\;2.0m/s^2$ were used to excite seated human body. Most of apparent mass curves showed two peaks in the frequency range of $4\sim9Hz$, first peak was clearer at the contact point of the seat and the hip, and the second one at the contact point of the backrest and the back. Both peak frequencies were found to move down to lower frequencies with increase of acceleration magnitude. Shapes of apparent mass curves were clearly different from those at erect posture especially in the frequency range around and above the second peak.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.105-108
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• 2004

This paper introduces a process of the development of a vibration test dummy for the posture of inclined seating. Experimental devices was invented to measure apparent mass curves on the contact point of the hip and the back of a seated human body. During the excitation of a rigid seat secured to a hydraulic exciter, force and acceleration signals were measured on the contact points to determine the apparent mass. In order to describe nonlinear characteristics of a human body, seven levels of Gaussian random signal were used for the base excitation. The modeling of the human body will be performed using measured apparent mass curves. The modeling will be done by June and the prototype of the test dummy will be invented in the following six months.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.33-44
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• 2003

This paper introduces attempts to obtain the'representative'characteristics of the apparent mass and mechanical impedance of seated Korean subjects under vertical vibration. Individual responses of the apparent mass and driving-point mechanical impedance obtained from forty-one Korean subjects are illustrated. Four kinds of vibration levels and three different sitting postures are selected to collect the responses of each subject. Those individual responses are used to estimate the 'mean' mechanical impedance, which may be expected to be a representative model to Korean subjects. Several interesting features of the estimated mechanical impedance are suggested and compared to those of ISO 5982.