Minimization of the vertical vibrations sustained by a tractor operator, by provision of a standard-type tractor seat suspension

Abstract

Experimental studies on the transmission and tolerance of vertical vibrations, caused by tractors, indicate that the tractor operator is exposed to low-frequency (0.5 to 11 Hz) and high-intensity vibrations, which are harmful to the body, causing disorders of the spine and supporting structures. The intensity of these “harmful” vibrations is reduced by providing a standard-type suspension to the tractor seat. In this paper, the coupled occupant-tractor system is modeled as a lumped parameter system. The composite model is analyzed, by computer simulation, for vertical vibrational responses, of the body parts, to (sinusoidal and transient) vertical vibrational inputs applied to the tractor wheels (as a simulation of the dynamic ground reaction caused by the motion of the tractor wheels over farm terrain and over a sudden obstruction). The parameters of the suspension system are selected such that the vertical vibrational responses of the body segments as well as chassis pitch vibrations are minimized in the above low-frequency range. The results show that, in comparison to the rigid seat, the standard-type seat suspension reduces the body segments' vertical and the chassis' pitch vibrational levels by 60 and 85%, respectively, thereby considerably improving the operator's riding comfort.