Development of a Nonlinear Tractor Model using in Constructing a Tractor Driving Simulator

Abstract. There are approximately 400 cases of fatal farm accidents each year in Japan. Among them, accidents involving agricultural tractors are frequent. There is an urgent need to reduce the number of tractor accidents and thus advance the safety and efficiency of agriculture. Meanwhile, model-based development (MBD) technology has rapidly progressed in recent years. Using MBD technology, the machinery design and control logic can be developed by computer simulation. On the basis of MBD technology, driving simulators are developed and used to improve the safety of automobiles. A tractor driving simulator is therefore promising technology with which to reduce the number of tractor accidents. However, a tractor driving simulator has not yet been constructed. A tractor driving simulator comprises three parts, namely a nonlinear tractor model, steering model, and driving and braking model. In this study, nonlinear tractor model is developed as a first step in constructing a tractor driving simulator. The tractor jumps under some conditions and experiences strong nonlinear vibration (i.e., chaotic vibration). The developed model reproduces this jumping process. Numerical experiments are conducted in which the developed model is excited by a sinusoidal road. The developed model jumps under some conditions and experiences nonlinear vibrations. The time series of strong nonlinear vibrations are analyzed by Fourier spectral analysis. Subharmonics and ultrasubharmonics are observed in the Fourier spectrum as evidence of nonlinear vibrations. The jumping process of the tractor is appropriately modeled using the developed nonlinear model. It is possible to construct a tractor driving simulator by connecting the developed model to a steering model and driving and braking model.