Unstable vibrations of Maglev and Hyperloop vehicle-guideway systems at small and large speeds

Hyperloop is a potential new transportation mode that is currently under development. It resembles Maglev in the sense that vehicles are magnetically or electromagnetically levitated/suspended, but Hyperloop is supposed to be operated in a low-pressure environment to minimize aerodynamic drag; this creates the opportunity to reach very high speeds without unacceptable energy consumption. In systems employing purely attractive magnetic suspension, active control is required to regulate/stabilize the electromagnetic force and maintain a constant air gap between the vehicle and the guideway. However, the space-dependent and speed-dependent flexibility of the guideway makes Hyperloop and Maglev systems susceptible to instabilities even when feedback control is applied. In this study, we discuss the relevance of the following instabilities: - oscillatory instability (flutter) at stand still or small speed - principal and combination parametric resonance at any speed - oscillatory instability (flutter) at very high speed In most of these, the flexibility of the guideway plays a rather crucial role. It can simply render the vehicle control inappropriate due to the flexibility that changes the dynamics of the system when designed based on the rigid-guideway assumption. On the other hand, it can also stabilize the system because of radiation damping (i.e., waves carrying energy away from the vibrating vehicle). Finally, the guideway can ‘actively’ destabilize the system when the so-called anomalous Doppler waves feedback energy from the guideway into the vehicle vibration.