| With the rapid development of national economy, the overall construction of expressway network and the great improvement of people's living standard, automobiles have gradually come into people's life and work, and become an indispensable means of transportation. Meanwhile, people have made greater demands on the comfort and security of automobiles. The suspension system is a critical component that can influence the automotive performance. The intelligent suspension system has real-time control according to the road surface conditions and the state of automobile's motion. Its adoption is an important approach to improving automotive comfort and security. Magnetorheological (MR) semi-active suspension applies MR technology to carry out the real-time control of its damp. Due to its good controllability, wide dynamic range, rapid response speed, low operating power requirement and comparatively simple structure, MR semi-active suspension has become one of the central research subjects in intelligent suspension field, and has also received considerable attention of global automobile manufactures. In this paper, the methods of theoretical analysis, numerical simulation and road testing are applied to study the dynamical characteristics of MR damper and semi-active suspension, the control strategies and the control system's design and realization of semi-active suspension. The main contributions of the dissertation include the following:1. The paper expounds the significance of the intelligent suspension research, reviews its history and development, summarizes the present situation and existing problems of MR fluids, MR dampers and MR semi-active suspension, and puts forward the main work aimed at the present problems of automotive MR semi-active suspension. The rheology equations of MR damper and the computation formula of damping force are derived from hydrodynamics theory, based on Newton fluid model or Bingham fluid model,flowing in annular duct or in parallel duct. And the force-displacement and force-velocity characteristics are also analyzed in this paper. In accordance with national standard and the technical demands for mini-automobiles, the MTS electric- liquid servo testing system is used to test the force-displacement ,force-velocity and force-temperature characteristics of the MR damper adopted in the paper. The change rules of theoretical damp2. force with that of tested damp force are compared, and also the main cause of the error is analyzed.3. The method and indicators used to evaluate the performance of the automotive suspension system are discussed. The road profile input model of random road surface and the dynamic model of quarter-car suspension is established. The transfer functions of sprung mass acceleration,suspension deflection and tire load relative to road disturbances are derived. With the numerical simulation, the suspension response in frequency domain of the mini-microbus at different speeds and on roads of different levels, and the influence of suspension parameter on the suspension transfer characteristic, as well as the time domain response of passive suspension for the impulse input are studied in the paper.4. The MR semi-active suspension model is established. The theoretical method of sky-hook control strategy and fuzzy control strategy is expounded. A new control strategy-the wavelet frequency control strategy is put forward. This strategy decomposes automotive vibration acceleration signal utilizing wavelet transform to judge the composition of present vibration frequency, thus to determine the magnitude of damping force. The sky-hook controller for vehicle semi-active suspension, and the fuzzy controller with the input of sprung mass absolute speed and the comparative speed between sprung mass and unsprung mass,wavelet frequency controller with the input of sprung mass vertical vibration acceleration are designed. MR semi-active suspension simulation system is established by using Matlab software and its corresponding toolboxes. After adopting the abo...
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