Feedback Stabilization of a Corkscrew Istabilty

An application is made of lumped feedback to achieve stability of a distributed electromechanical system. A conducting elastic wire, placed in an axial magnetic field and carrying a current, exhibits instability at a certain threshold of magnetic pressure. The two dimensional transverse displacement of the wire is sampled and these signals are used to produce proportional feedback forces which allow stable equilibrium to be restored. A stability diagram is determined indicating the minimum feedback force to prevent static instability. For one station feedback, there is a maximum allowable feedback to prevent overstability. The pinch confinement of a plasma suffers from a similar corkscrew instability.