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The Semi-Active Control Of Vehicle Suspension Systems Based On Magnetorheological Dampers

Posted on:2003-03-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:J S WengFull Text:PDF
GTID:1102360062450325Subject:Solid mechanics
Abstract/Summary:PDF Full Text Request
At present, semi-active control suspension systems have received a great deal of attention in academe and industrial circles to improve ride comfort and road holding and handling stability. The damper with dynamically variable damping properties is one of the key elements for semi-active suspension systems. Magneto-rheological (MR) fluid dampers have recently emerged as enabling technology for implementing semi-active control in a variety of application because of their mechanical simplicity, low operating power requirements, environmental robustness, and demonstrated potential for developing forces sufficient for applications. MR dampers use MR fluids with a change in Theological behavior when a magnetic field is applied to produce controllable damping. In the dissertation, a state-of-the-art semi-active control suspension system in which the MR dampers are used to replace the passive dampers as the semi-active control actuators has been proposed and developed based on the analytical and experimental investigations of the MR fluid and the MR damper. The theoretically analytical, simulation and experimental investigations are conducted to characterize the dynamical performance and to develop the semi-active control technology of the MR damping semi-active suspension system. The main contributions of the dissertation are as follows:On the basis of experimental results, the operational effects, such as the magnitude of magnetic field, the temperature and the rate of shear strain, on the shear stress of the MR fluid are shown and models of the quasi-Bingham model and a nonlinear model for the shear stress of the MR fluid also are developed, in which the characteristic of "shear-thin" of the MR fluid is described. The approximate equation is established to calculate accurately the output force of the MR damper based on the developed MR fluid model by the theoretically analytical investigations. This dissertation also presents the equivalent stiffness and damping models and the nonlinear hysteresis and saturation model of a kind of the MR damper developed by the experimental testing and modeling in order to describe accurately characteristics of the MR damper. In addition, the operational effects, such as the magnitude of voltage (the magnitude of the magnetic field), the amplitude and frequency of excitation, on the parameters of the models are discussed according to the experimental results.The theoretical investigations are carried out in two phases. In phase 1,the dynamical properties in the time and frequent domains of the simple, two-degree-of-freedom models of passive, "sky-hook" and "ground-hook" damping suspension systems are examined by Laplace transform. In phase 2, the nonlinear dynamical properties of the simple, two-degree-of-freedom model of MR damping suspensionsystems are explored by the method of equivalent linearization. The asmptotic stability of the free vibration for the MR damping semi-active suspension system is determined by the Lyapunov stability theory.Several semi-active control algorithms used in the semi-active suspension system with MR dampers are proposed and developed including the "on-off" voltage controller, the continuously linear variable voltage controller, the modulated continuously linear variable voltage controller based on "sky-hook" damping concept and the hybrid controller based on the combination of "sky-hook" damping concept and "ground-hook" damping concept and the Fuzzy logic controllers using measurements of the relative displacement between the sprung and unsprung mass or the absolute acceleration of the sprung mass as the input variables of fuzzy logic controllers. The simulation models were prepared in Matlab?Simulink?Fuzzy toolbox programs. The experiment setup of the semi-active suspension system with MR dampers in the lab has been designed and developed. The effectiveness of the proposed the semi-active suspension system with MR dampers is successfully verified by evaluating the dynamical characteristics of different semi-active control algorithm...
Keywords/Search Tags:Vehicles, Suspension systems, Magneto-rheological damper, Modeling, Vibration, Semi-active control, Fuzzy logic control
PDF Full Text Request
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