Studies on the Vibration of Tractors and Human Response (II)

Dynamic Response Characteristics of Operator Seated on Tractor

Abstract

To obtain the dynamic response characteristics of operators under vertical vibrations, we sought the correlations between the acceleration of a vibrator or a tractor seat and the acceleration of the waist, shoulder and head of operator seated on it.
(1) Assuming that man-machine system was linear, we obtained the satisfactory results on human dynamic response charactristics by spectrum analysis.
(2) Resonant frequencies of human body were in the low frequency area (under 10Hz). Namely, they were in the nearly 5Hz range at the waist and the head and nearly 3.5Hz range at the shoulder. But in a strained posture larger resonance appeared at the sholder in the nearly 9Hz range.
(3) The transmissibility (the ratio of the body part acceleration amplitude to seat acceleration amplitude) remarkably decreased over 10-20Hz range and the values were under 0.1. The acceleration power spectral density (P. S. D) of the waist increased at the frequency affected by engine revolution, but the P. S. D of other parts hardly varied over 50Hz range.