Improving the capacity of tire normal force via variable stiffness and damping suspension system

Tire normal force of a vehicle equipped with a variable stiffness and damping (VSVD) suspension system is studied via numerical simulation in this paper. The main purpose of the paper is to illustrate the effects of VSVD suspension system on the capacity of tire normal force. Firstly, a modified suspension system and its variable stiffness and damping characteristics are presented based on a conventional suspension system. With the application of adjustable suspension system in vehicle, the effects of equivalent stiffness of suspension system on vehicle performance are analyzed by the term of load transfer at tires when cornering. By using a reference model, a simple on/off control strategy is developed to improve normal forces at tires and a fuzzy control strategy to model Direct Yaw moment Control (DYC) based on yaw rate is also developed to show the required longitudinal force. Finally, numerical simulations are carried out to demonstrate the important role of VSVD in improving tire normal force and then ameliorating vehicle lateral stability. It is shown from the results that the normal force at tires can be increased through the application of VSVD suspension system. It also indicates that DYC would be much efficient when implementing this system.