剛体円環モデルを用いた農用タイヤのパラメータ同定

Abstract

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, it is confirmed that the dynamic behavior of rolling tire is influenced by the vibration characteristics of the tire and only the rigid modes can affect the rolling tire behavior. Therefore, we modeled the tire as a circular rigid ring supported on an elastic foundation with a contact patch slip model in order to estimate the lug excitation force. An important aspect of tire modelling is the identification of the tire model parameters. In this research, the tire wheel system is modeled as a circular rigid ring connected to the wheel through the tire sidewalls with a contact patch slip model. As for an agricultural tire, the out-of-plane dynamics is also important because of cross-stich lugs. This model can describe not only the in-plane tire dynamics but also out-of-plane tire dynamics. The equations of motion of the dynamic tire model are derived and the equations of motion are rearranged to describe the in-plane and the out-of-plane dynamics. From the rearranged equations of motion, frequency equations are derived separately and calculation procedure for obtaining the natural frequencies of the rigid ring model is formulated. Furthermore, the model parameters are identified by minimizing the difference between measured and calculated natural frequencies using Downhill Simplex method. The natural frequencies and natural modes predicted by the calculation using the identified model parameters show good agreement with those obtained experimentally.