Thrust and levitation control of permanent magnet linear synchronous motor using optimal regulator theory

In this paper, the optimal regulator theory is applied to control the thrust and levitation forces of a PM linear synchronous motor (PM-LSM). Applying the theory, non-linear state equations must be linearized around an equilibrium point, and stable behavior of the PM-LSM is guaranteed only near the equilibrium point. However, since the velocity must be varied, system responses may be deteriorated if the velocity reference is far from the equilibrium point. Therefore it is necessary to compensate for the non-linear terms to establish a stable control system over a wide velocity range. This paper proposes one compensation method. Responses to reference changes and disturbance changes with and without the compensation are investigated by simulation, and the usefulness of the compensation method is verified by it.