Research On Motion Stability Of Maglev Vehicles

In this thesis, the research on motion stability of maglev vehicles are investigated, andthe following results are given.Firstly, the nonlinear dynamic model of maglev vehicles with single and twosuspensions is presented based on the rigid guideways. By the Hurwitz criterion, thedomain where the equilibrium is stable under PD control is deduced and illustrated in theplane of the control parameters. The two boundaries of the stable domain of the equilibriumare corresponding to the conditions of Hopf and saddle-node bifurcations respectively.According to the numerical simulations which are consistent with theoretical analysis, it isfound that the response may be divergent corresponding to parameter domain where theequilibrium is unstable, periodic corresponding to the boundary where Hopf bifurcationoccurs, or a new equilibrium corresponding to the boundary where saddle-node bifurcationoccurs. By comparison, it is shown that displacement feedback has better controlperformance than velocity feedback.Secondly, the dynamical analysis of coupled vehicle-guideway system in verticaldirection is presented with the consideration that the vehicle is modeled as a single-magnetsuspension with one degree and the guideway is simplified as a simply supportedEuler-Bernoulli beam with uniform cross-section. By the Hurwitz criterion, the conditionsfor Hopf bifurcation and Saddle-node bifurcation under PD control are deduced for thecontrol parameters to give the boundaries between the stable and unstable domains. Thecomprehensive comparison is carried out through the analytical and simulation resultsbetween the case of rigid and flexible guideways. It is concluded that the stable domain inthe plane of the control parameters for the equilibrium is much smaller even when the firstmode of flexible guideway is considered, by which it is meant that the flexibility ofguideway is necessary for dynamical analysis and control design.Finally, the comparison between the cases when only the first mode and the first twosymmetrical modes of flexible guideway are considered is also presented, it is shown thatthe influence of high-order mode to the magnetic levitation system dynamic behavior isnegligible by the comparison between the case of the first mode and the first two modes offlexible guideway are considered. It is found that the equilibrium may results in a newequilibrium, periodic or divergence motion after the system is perturbed when the controlparameters are not in the stable domain. Numerical simulations are in good agreement withthe analytical predictions no matter the equilibrium is stable or not.