The objective of this study is to clarify the vibration generation mechanism of agricultural machinery caused by the interaction between the tire lugs and the road surface. It is important to investigate the lug excitation force occurring on a rolling agricultural tire in order to clarify the vibration generation mechanism. In our previous study, we modelled the agricultural tire as a three-dimensional rigid ring model (SWIFT model). Further, the frequency equations of SWIFT model are derived and the model parameters are identified by minimizing the difference between measured and calculated natural frequencies. In order to identify lug excitation force, shaft displacement and shaft force during rolling motion are measured three-dimensionally by rolling test and lug excitation force in longitudinal, vertical and lateral direction are identified. From the obtained results, shaft force characteristics and lug excitation force characteristics are investigated. As a result, there is a correlation between shaft force and lug excitation force and it has been confirmed that both characteristics are influenced by the vibration characteristics of the tire. However, the transfer characteristics between lug excitation force (as input) and shaft force (as output) are not investigated.
In this study, amplitude magnification and phase difference are analyzed as the transfer characteristics of lug excitation force and shaft force. From the obtained results, the influence of vibration characteristics of the tire on transfer characteristics are investigated.