Active mitigation of self-excited vibrations of a magnetic track brake

Abstract

Magnetic track brakes (mtbs) are additional braking systems used in railway vehicles at emergency situations and low adhesion conditions. Operation at low velocities can cause harmful self-excited vibrations, which must be avoided at all circumstances. Few passive countermeasures are already published, but active vibration control of an mtb lacks in literature so far. In this paper an active vibration control to diminish self-excited vibrations, based on reducing the energy, drawn by the oscillating system, is studied. Considering a minimal model of the mtb, the energy input depends on the electromagnetic-mechanical coupling and the friction force in the mtb—rail contact. The obtained equation of this energy reveal a dependency of the phase shift, between magnetic flux and the oscillatory mechanical motion. A control law for the input voltage is obtained to reach a specific phase shift reducing the energy input and oscillating amplitudes.