Impact dynamics model for a nonlinear bouncing tractor during inclined passage

Abstract

Globally, tractor overturning accidents are a serious problem in agriculture. Tractor overturning not only threatens the life and health of famers but it can be major obstruction towards farm automation. In Japan, small tractors are used in harsh running environments, such as on rough farm roads, steep passage slopes, and narrow inclined side paths. Violent vibrations can occurs in the tractor and the wheels of the tractor sometimes depart from the ground. This phenomenon is called “bouncing” and leads to impact dynamics which are equivalent to the bouncing ball. Bouncing is typical nonlinear dynamics which causes excessive vibration, along with sideslip and poor steering performance which can lead to overturning. Bouncing becomes particularly serious when tractors run on steep slopes such as from a paddy field to a farm road. The present study analysed an impact dynamics model of a nonlinear two-dimensional bouncing tractor on steep passage slopes solved using numerical simulation. First, frequency response analysis was employed to investigate basic characteristics of nonlinear bouncing tractor model. Discontinuous responses, which are typical of nonlinear phenomenon, were observed in the frequency response curve. Next, numerical experiments of the tractor running on a steep passage slope were conducted based on a real accident case that occurred in Japan. Travel velocity of tractor and angle of passage slope were taken as control parameters and varied. Discontinuous responses were observed as control parameters were varied. Results indicated that nonlinear bouncing tractor model has strong parameter sensitivity which can cause sudden unpredictable phenomenon, such as violent vibration and sideslip, and overturning accidents.