Abstract
KEYWORDS vehicle dynamics, steering system, multibody suspension, static joint friction, on-center handling feel
ABSTRACT
Research and/or Engineering Questions/Objective
There are three main categories of influencing factors on on-center handling feel, which are mechanical characteristics of steering system, the motor characteristics including EPS control logic, and suspension characteristics. Whereas the researches considering EPS motor control system and the effect of steering system have been continuously on progress, the study considering the effect of suspension friction characteristics has been scarcely conducted. The objective of this study is analyzing the initial transient characteristics of on-center handling feel index with suspension and steering system joints friction as simple static spring friction models.
Methodology
Before analyzing dynamic handling feel, it should be studied first that how kinematic and compliance (K&C) characteristics of suspension changes from joint friction modeling. For this, quasi-static front suspension multi-body model is used. This suspension model includes spring friction model for joints, and this model can be used in both static and dynamic analysis because of this model is assumed as a function between displacement and friction force/torque. The parametric study based on this suspension model makes it able to figure out the influence of joint friction on suspension K&C characteristics and full vehicle on-center handling feel. In turn, relation formulas are used to analyze the initial transient period characteristics of steering torque gradient (STG).
Results
In the paper, the influence of suspension and steering joint friction modeling on initial transient period characteristics of on-center handling will be presented. The main finding is that the initial gradient of spring friction model is the most important factor to predict the initial slope of a graph for extracting on-center handling feel indices. The result using Dahl friction model shows a very steep slope, however, in the real test results generally shows less steep slopes. Therefore, using spring friction model in on-center handling analysis could be more exact method for both statically and dynamically.