Reproducing the Motorcycle Equation of Motion with Lumped Stiffness on Multi-Body Dynamics Model

A new simulation model for motorcycle motion is presented. The model was reproduced the equation of motion which called 10 degrees of freedom (10-DoF) motorcycle model using multi-body dynamics. There are some good reasons to reconstruct equation model by multi-body dynamics, because computer technology helped development of tools which is versatile to expand model. Straight line stability characteristics of motorcycle have been studied by using an equation of motion model for a long time. This model was originally developed by Sharp as a 4-DoF model, later Aoki developed 10-DoF model by adding 6-DoF to take frame stiffness into account. The eigenvalues of the Weave and Wobble mode showed some disagreement between the equation of motion model and the new multi-body dynamics model. The frame lateral bending is represented by the “equilibrium of lateral force” in the 10-DoF equation of motion. It turned out that “lateral force at bending Point” was not expressed in the equation. To make them equivalent, the expression of the equilibrium was changed from “Lateral force” to “moments around bending point”. As a result of this modification, the multi-body dynamics model showed good agreement with equation of motion model.