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Repeated Bouncing Process of Farm Tractors from the Nonlinear Dynamics Perspective

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 270-278 in Automation Technology for Off-Road Equipment, Proceedings of the July 26-27, 2002 Conference (Chicago, Illinois, USA)  701P0502.(doi:10.13031/2013.10016)
Authors:   L. O. Garciano, R. Torisu, K. Sakai, and J. Takeda
Keywords:   Repeated bouncing process, Unstuck and impact period, Nonlinear dynamics, Relaxation oscillations, Nonlinear resonance

Repeated bouncing process of a traveling tractor occurs on certain road conditions when the wheels become unstuck that means no contact with the road surface. Furthermore, the impact after the unstuck period produces violent vibrations that cause severe discomfort to the operator and shock loading that may cause fatigue failure on the structural components of a tractor or the linkage of tractor-implement system.

This paper investigates the bouncing process and impact phenomenon of a traveling tractor by transient response test during standstill and steady state response test of continuous pulse input using an artificial test track.

In the results, the artificial test track formed of triangular shape angle irons is a multiple input excitation because it contains fundamental forced frequency with higher harmonics, thus it produced nonlinear resonance. The time series demonstrates the existence of bouncing process with a flat –1g-acceleration level that indicates unstuck period of the wheels followed by an impact period producing violent vibrations in the low frequency range of 0~10 Hz.

Noise due to impact and relaxation oscillation due to nonlinear damping characteristics of tires are visualized by the phase portrait. Two period 3-doubling scenarios are estimated to occur that indicates the onset of the bouncing process and major dynamic instability. The change of the embedding dimension of the attractor implies increase complexity of tractor dynamics as the forward speed is increased.

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