Dynamic stability of an electromagnetic suspension maglev vehicle under steady aerodynamic load

Abstract

In this study, the suspension stability of a maglev vehicle is investigated under steady aerodynamic load. The dynamics of the maglev vehicle in the vertical direction are modelled by considering aerodynamic lift and pitching moment, and this model is adopted to investigate how the aerodynamic load influences the suspension stability by analysing the critical speed by means of eigenvalue analysis and direct integration. Doing so reveals three modes of suspension failure: (i) an upward aerodynamic load or pitching moment can give rise to a dynamic instability, (ii) a downward aerodynamic load can give rise to a static instability and (iii) the electromagnet becomes locked in the guide-way because the vertical aerodynamic force borne by the electromagnet exceeds the vehicle weight borne by it, and the electromagnetic force cannot adjust the suspension gap. In essence, failure modes (i) and (ii) correspond to motion stability when the maglev vehicle system is perturbed by a small amount, whereas failure mode (iii) is similar to the electromagnet holding the track in the event of control failure, albeit by a different mechanism. Each suspension failure mode has its own critical speed, and how that speed depends on the aerodynamic coefficients and feedback control gains is determined.