Experimental Study of Tire-Wheel-Suspension Dynamics in Rolling over Cleat and Abrupt Braking Conditions

Abstract

ABSTRACT The braking performance of recent vehicles is controlled by the interaction between the antilock braking system (ABS) and the transmitted force between road and tire. Because of tire and suspension elasticity, an abrupt braking or the ABS regulation initiates tire belt and wheel axle oscillations, which lead to a closed loop of acceleration and force transmission in the tire-wheel-suspension assembly in both translational and rotational directions. As a result, the oscillation of wheel slip and wheel load can influence the force transmission potential in the contact patch and thus the braking distance as well. The objective of the presented study is to investigate the influence of the tire-wheel-suspension dynamics on the force transmission potential between tire and road. To obtain acceleration and force dynamics in the tire-wheel-suspension assembly without inducing the influence from other vehicle components, a McPherson suspension was isolated from a real car and adapted to the inner drum test bench at the Karlsruhe Institute of Technology, Institute of Vehicle System Technology. After mounting different tires, measurements were carried out under various driving conditions. First, tire measurements with a measuring hub were done on the test bench to obtain both quasistatic characteristics and dynamic response in rolling over cleat. Second, different tire-wheel-suspension assemblies were driven on the test bench while the wheel brake was initiated by a hydraulic braking system based on a modified ESP control unit. This modified unit allows generation of abrupt braking pressure slopes by a direct control of the valves. The accelerations of different wheel-suspension components and forces in the links were measured. In this article, the experimental study of the dynamics of a run-flat and a standard tire and their respective coupled assembly with the suspension excited by rolling over cleat and abrupt braking is presented. After a description of the experimental setup, the results of tire-wheel-suspension dynamics of two different tires will be analyzed, interpreted, and compared. Furthermore, a simulation model of the tire-wheel-suspension assembly with the FTire model and dynamic models of suspension components will be built up.