Delivered by Ingenta to: University of Leicester IP : 143.210.108.119 Sun, 04 Sep 2011 05:25:24 Copyright © 2011 American Scientific Publishers All rights reserved Printed in the United States of America RESEARC H ARTICLE Advanced Science Letters V ol. 4, 953–957, 2011 Sliding Mode Control Design of Active Vehicle Suspension Systems with Two-Time Scale Submodels Feng Qiao 1∗ , Shuang Sun 1 , Jia Sun 2 , and Quanming Zhu 3 1 Faculty of Information and Control Engineering, Shenyang Jianzhu University, Shenyang, Liaoning 110168, China 2 Faculty of Mechnical Engineering, Shenyang Jianzhu University, Shenyang, Liaoning 110168, China 3 Bristol Institute of Technology, University of the West of England, Bristol BS16 1QY, UK A novel sliding mode control strategy is proposed in this paper to deal with the design of active vehicle sus- pension control systems based on two-time scale singularly perturbed dynamic model. The proposed control strategy only employs two measured state variables to control the suspension systems which are commonly controlled by four measured variables for quarter vehicle suspension system. The simulation results show that the proposed control strategy is effective and superior to the passive vehicle suspension system and the full feedback optimal controller in performance. Keywords: Sliding Mode Control, Active V ehicle Suspension, Tw o-Time Scale, Singular Perturbation. 1. INTR ODUCTION The rese arch and dev elop ment of vehicle susp ensio n syste ms (VSSs) has been the intense subject for engineers and researchers recently in vehicle manufacturing industry. A good VSS should possess following the characteristics as: 1–2 (1) isolating the veh icle body from both road distu rban ces and the inertial disturbances associated with cornering and braking or acceleration; (2) minimising the vertica l forc es transmit ted to the vehicle for passenger ride comfort; and (3) maintaining good hand ling of tyre- to-r oad contac t on the all four wheels. A conventional VSS is consisted of springs and dampers which are called a passive vehicle suspension system (PVSS). It has the ability to store energy via a spring and to dissipate it via a damper. But the springs and dampers do not provide energy to the system, and their parameters are generally fixed, being designed only to achieve a limited rate of compromise between road holding, load carrying and ride comfort. Active vehicle suspension system (AVSS) has been proposed to improve the characteristics of PVSS. An AVSS is a suspen- sion system with an augmented actuator to passive components to provide additional forces to the system, it normally includes ∗ Author to whom correspondence should be addressed. senso rs to meas ure suspensi on var iables such as bod y veloc- ity, suspension displacement, wheel velocity and wheel or body acceleration. The additional forces it provides to the system are determined by the control law using the feedback signals from the sensors to keep passengers ride comfort and vehicle handling and safety. Ther e hav e been many control strategi es cont ributed to the control law design for AVSS, the strategies can be classified into following categories: optimal state feedback control, 3 intelligent control, 4–5 sliding mode control (SMC), 6–7 adaptive control, 8–9 and backstepping control. 10 It is proposed, in this paper, a new SMC control strategy for a quarter AVSS, the new control algorithm takes the advantages of the special structure of the system dynamic model of AVSS, and separates the mod el into two-time scale submodels: slow submodel and fast submodel based on the singular perturbation theory. So the reduced order SMC (RSMC) is designed to tackle to control problems which are usually dealt with by four state variables for a quarter AVSS. Here, the proposed control strategy uses only two measured state variables, and the simulation results show that it gets better results than the full state feedback optimal controller. The remainder of the paper is organised as follow. Section 2 gives the mathematical dynamics of a quarter vehicle suspension system in two-degrees of freedom (DOF), and defines the objec- tive of the controller design. RSMC controller is discussed and designed in Section 3; in Section 4, simulation studies are made Adv. Sci. Lett. Vol. 4, No. 3, 2011 19 36 -6 61 2/ 2011/4 /9 53 /0 05 doi:10.1166/asl. 2011.1572 953
