Research On The MR Semi-Active Suspension System And Its Control Strategy

As one of the most essential component of modern vehicles, the suspension system plays an important role in the designing and using vehicles. Among different semi-active suspensions, the system based on MR damper has high research value and great application prospect. Research on that system usually involves design of the suspension system and damper, system modeling and design of control schemes, etc. Through dynamics modeling and feature analysis, this article established effective control schemes for MR-damper-based semi-active suspension system.This article introduced mechanisms and characteristics of semi-active suspension system, analyzed the rheological mechanism and mechanical characteristics of MRF, and explained its working principles in detail. Then the article summarized main difficulties in system modeling and control strategy design of the whole MR semi-active suspension, which lay the foundation for later analysis in the article. Then the article established an improved non-linear model based on Bouc-Wen parameterized model for MR damper and obtained the formulas of the controlling current and damping force. The analysis of the external characteristics of MR damper is also performed. Meanwhile, the article established a quarter model for two-degree vehicle semi-active suspension. The MATLAB/Simulink simulation model is set up to analyze three attributes of the suspension:body acceleration, suspension dynamic travel,tyre dynamic load, and determined the effects of body damping coefficient on suspension performance. The analysis on these problems provided theoretical reference and directions for research on the design of control schemes.Using random road surface model in time domain and targeting for the structural characteristics of suspension system, the article further summarized two control ideas. For one idea, the article began with the classic ideal skyhook control strategy, and further went onto its active realization. Ground hook control strategy was introduced later to improve the general performance, and finally state judge was added to generate the semi-active control strategy. For the other idea, a three-dimensional control structure was proposed and then simplified into a two-dimensional structure, and a asymmetric fuzzy control rules for damper's excitation current was obtained by introducing the damper's design idea. Finally, a simulation experiment was conducted to compare the control effect under the random road surfaces. The experiment results indicated that both control strategy are effective and feasible, and can improve the ride comfort, driving safety and operating stability. Moreover, the fuzzy control strategy can restrain the body acceleration and tyre dynamic load more significantly, which improved the suspension's overall performance remarkably.