Leino S., Marjanen Y., Launis S., Kortelainen J.

In order to develop more user-friendly mobile machinery, more information on the connection between the human comfort experience and measurable quantities, like the motion of the operators seat, is needed. In this paper we describe a study on the mechanical response and the subjective comfort feeling of a human exposed to high level vibration. Experimental tests were accomplished in a laboratory motion platform, which simulated the vibration excitation that operator undergoes in heavy mobile machine. The test excitations were based on field measurements and included such activities as cultivation, moving in forest and on gravel road. Vibration response of 23 test persons were measured by four tri-axial accelerometers. The test persons were equipped with heart rate monitor. Pressure distribution applied on the seat cushion under the seated person was measured with pressure sensitive foil having multiple sensing points on matrix-like measuring grid. The measurements were recorded by two video cameras. Result of the video analysis was the 3D motion data of the different marker points on the body, which was then synchronized with the other measurement data for further analysis. The test persons evaluated the vibration exposure based on a five scale comfort criteria and described their subjective experience. RMS-values, based on the ISO 2631-1 standard, were calculated from the acceleration data from the floor, seat and head of the test persons. The human comfort is a sum of many different variables, and the analysis of the test data is complicated due to individual differences. We show in this paper a new insight on how the human body moves under vibration and what variables affect the comfort level. A simulation model based control algorithm is proposed to include the comfort aspect in the active vibration damping system.