Three-dimensional dynamics of a three-axle vehicle considering the suspension geometry according to the kinematic transformers method

摘要

The purpose of this work is to model the dynamics of a three-dimensional three-axle vehicle subjected to certain excitations from the ground and considering the geometry and inertia of the suspension elements according to the “kinematic transformers” method. The chassis is considered a rigid body with six degrees of freedom (three positions and rotations). The tire is a compliant element, which receives vibration from the ground and transmits to the wheel. Unlike simpler computational models, which make a direct connection between the wheel and the chassis by means of a spring and damper, the influence of the suspension geometry and inertia of its elements are considered. In this case of study, the suspension studied is the independent MacPherson in each wheel, although the methodology would be applied to other kind of suspensions, once its geometry is known. The kinematic transformers method is applied to study the cinematics of the suspension. It uses the minimum number of kinematic equations, allowing an efficient solution to describe the movement of the mechanism when implemented computationally. Combining the kinematic transformers method with the d'Alembert principle for the solution of the dynamics of the mechanism, it is possible to describe the kinematic and dynamic behavior over time. The vehicle has a front and intermediate steering axles, and a rear axle with no steering. Thus, the degrees of freedom of the steering rack and wheel rotation are considered in the formulation, although they do not variate. The intention is to, firstly, consider just the effects of vibration in the chassis without their variation, and secondly, present this model as a motivation for future works, considering their variation. The MATLAB platform was used for computational simulation.