Wheelbase Preview Active Suspension Control to Improve Vehicle Ride Comfort based on Front-Wheel Acceleration Sensing

Abstract

Active and semi-active suspension systems for passenger vehicles have been a very active area of research for several decades owing to their potential to improve the ride comfort and handling performance. It is well known that active suspensions provide better performance and more functions compared to semi-active suspensions. The main functions of active suspensions are vehicle height adjustment, ride quality improvement, and attitude control. Some active suspensions have been implemented and commercialized on high performance and luxury vehicle these days. For example, Hydractive suspension by Citroen, active body control (ABC) system by Mercedes-Benz, and anti-roll control (ARS) system by BMW have been developed. Active suspensions have even greater potential if preview information of the oncoming road height profile is available. There are various ongoing projects which are trying to achieve better driving performance using road preview information. Mercedes-Benz introduced the worlds first actively preview controlled suspension system by detecting road surface undulations in advance. BMW is trying to develop video image processing system for suspension control. Volkswagen has undertaken researches to prepare and operate suspension parts by road sensing with radar/ laser sensors. Honda holds a patent for adaptive active suspension and aware vehicle network system.<br/> From a careful review of considerable amount of literature, active suspension and preview control technology has the potential to promote both safety and convenience of passengers. However, the current state-of-the-art in preview active suspension technology has two main challenges. First, the developed suspension control approaches require information on signals which may be difficult to access such as suspension stroke speed or tire deflection. Second, it requires precise, expensive sensors to detect road information such as a laser scanner. While the cost of these sensors is going down, integrating these sensors include special considerations and represent yet another barrier to adoption. <br/> Therefore, this dissertation focused on developing a partial preview control algorithm for low-bandwidth active suspension systems. In order to cope with the unknown road disturbance, a novel vertical vehicle model has been adopted. The state variables for suspension control were estimated using easily accessible measurements. The vertical acceleration information of front wheels is used to obtain preview control inputs for rear suspension actuators. From the present driving mode by a mode selector, the control objective is determined to be height control, attitude control, or ride comfort control.<br/> In the remainder of this thesis, we will provide an overview of the overall architecture of the proposed active suspension control algorithm. The performance of the proposed algorithm has been verified via computer simulations and vehicle tests. The results show the enhanced vehicle driving performance by the proposed suspension control and state estimation algorithm.