Chaos Analysis And Control Of Maglev Vehicle Suspension

As one of the most essential component of modern vehicle, the riding comfort and the handing stability of vehicle are directly affected by the character of the suspension system. Among different semi-active suspension, the system with Magneto_rheological Damper (MRD) is paid more attention in automobile engineering community at home and abroad because of the advantages such as simple structure, low energy consuming and easily realizable. However, MRD has strong hysteresis characteristics, which leads to some complicated nonlinear dynamic behaviors in the MR suspension system because of excitation, which becomes one of the most important restriction factors that MR suspension system have not been really popularized. Therefore, it is necessary to investigate the nonlinear dynamic characteristics of MR suspension system and then design semi-active controller with good performance.Firstly, the dynamic equation of 2-DOF quarter-car magneto-rheological suspension is established by applying the hysteretic force-velocity model of magneto-rheological damper. The bifurcation properties affected by the frequency and amplitude of harmonic excitation are deeply studied through employing phase diagram, Poincare map and power spectrum. In addition, according to the principle of semi-active control, the sensitivity of control current is further investigated in the low-bandwidth and middle-bandwidth.Secondly, a two-dimensional fuzzy controller is proposed through three attributes of the suspension:body acceleration, suspension dynamic travel and tyre dynamic load. The inputs of this controller are composed of body acceleration and MRD’s relative velocity, and the output is MRD’s excitation current. The control strategy is further verified by simulation under harmonic excitation and random excitation. Finally, the fuzzy sliding mode controller is proposed by combining sliding mode control and fuzzy control, which can transform chaos vibration into stable periodic orbit in order to suppress its adverse effects. Moreover, the effectiveness of this controller is demonstrated by contrasting the simulation results of sliding mode control in frequency domain and time domain.In this thesis, the nonlinear dynamic behavior of MR suspension is investigated, and the effective composite control strategy is also proposed, which build a theoretical foundation for further study the nonlinear mechanism and control of vehicle suspension system.