Human Body under Two-Directional Random Vibration

Abstract

Human body behaviour under the influence of two-directional random vibrations is of great importance for optimal motor vehicle design. Efforts are being made in order to discover as much information about the influence of vibration on human body as possible. References show that the most attention has been paid to vertical vibration, although intensive research has been performed lately on the other sorts of excitation. This paper shows the results of the investigation of behaviour of human body, in seated position, under the influence of random two-directional (fore and aft and vertical vibration). The investigation is performed using an electro-hydraulic simulator, on a group of 18 healthy male participants. Subjects are asked to adjust level of fore and aft excitation in order to give the same sensation as vertical excitation. Experiments are performed in order to give results which might improve human body modeling in driving conditions. Excitation amplitudes (0, 55, 1, 75 and 2, 25 m/s2 R.M.S.) and seat backrest conditions (with (K) and without inclination (S)) were varied. Data results were analysed, and partial coherent and transfer functions analysis has been performed and results are given in detail. Human body transmissibility characteristics, under two directional random excitations, depend on its spatial position. Two directional random excitations affect human body transfer functions, which points out the fact that it behaves like a nonlinear dynamic system. This should be taken into consideration in synthesis of biodynamic vibration models of human body.