Abstract
Keywords: Vehicle Stability Control, Integrated Chassis Control, Co-simulation
Mechatronics and active control systems are playing an ever increasing role in automobiles. Today´s modern vehicles typically include more than 40 actively controlled systems that play a major role in vehicle directional stability, ride comfort and safety. Several significant control systems, such as anti-lock braking system (ABS), active suspension system, traction control system, active yaw control and so forth, are being popularly used in automobile industries. Many theories and design methods for active yaw control, anti-lock braking system and active suspension system have been proposed individually by several literatures for decades (Anthony and Zak, 2000; Beyer et al, 1993; Bowman, 1993; Wei-En-Ting and Jung-Shan, 2003). Various researchers have considered slip-ratio control of anti-lock braking systems in the use of sliding mode control schemes (Bowman, 1993; Rajamani, 2005). As to the design of active suspensions, the improvement of ride comfort is the major objective to be emphasized. A novel nonlinear backstepping design for a quarter-car active suspension system was developed (Park, 1999) which aims to improve the trade-off between the ride quality of passenger comfort and the utilization of suspension travel. For further improving vehicle handling and stability, yaw moment control has been studied and developed by controlling braking/driving force distribution to individual wheels as a strategy for driver support systems (Rajamani, 2005).
At present these systems generally work independently, but it is widely accepted that integration of these stand alone systems will lead to improved vehicle dynamic performance. In addition, the sharing of precious sensors and information will then also be possible. Both the automotive industry and the end users will be the direct benefactors of this research. Recently, there are some integrated studies which combine the previously mentioned subsystems in order to control vehicle dynamic states to reach better efficiency. For example, the concept of integrating anti-lock braking systems with active suspensions has been investigated (Wei-En-Ting and Jung-Shan, 2003). Researchers (Nicholas Cooper et al 2005) have investigated the effect of integrating active driveline and active suspension on improving vehicle dynamics. Few automotive manufacturers have launched their products with integrated vehicle control systems to improve the current level of vehicle dynamics. But successful integration is still largely in the research phase.
The overall goal of this paper is to take advantage of active suspensions combined with vehicle stability control to improve the vehicle dynamics performance in emergency situations. This is objective is realized by the integration of two specific vehicle sub-systems: a brake based Vehicle Stability Control (VSC) and an Active Suspension System (ASS). The research methodologies to be used include mathematical modeling and computer simulation to establish where co-existence is possible, followed by the development of suitable control strategies/algorithms for their successful integration. In this paper the improved performance objectives established from using the integrated approach are defined as a reduction in yaw rate and vehicle body slip angle and better handling capabilities.