Dynamic Stability of Repulsive Magnetic Levitation System : 3rd Report, Optimal Control of Active Primary Suspension

Abstract

Magnetically levitated (MAGLEV) vehicle systems have been studied as the future high-speed transportation. It is especially important to investigate the dynamic characteristics for running stability, safety and ride quality at high speeds. This paper deals with the vibration control problem of a two-degree-of-freedom vehicle-suspension model of repulsive MAGLEV systems; Although the repulsive MAGLEV system is inherently stable, the damping force is not large enough to suppress the vibration excited by guideway irregularity. In order to improve the vibration characteristics, there are two approaches; one 6f them is through secondary suspension design and the other, primary suspension design. The first approach gives a limit of vibration control because of the existence of an invariant point in the frequency response of car-body acceleration. This paper investigates the second approach, that is, direct magnetic force control of the MAGLEV systems. For this purpose the primary suspension is designed as a hybrid magnet configuration of a permanent magnet and an additional electromagnet of which the current is optimally controlled by LQG theory. The experimental and theoretical results show that the car body and levitation gap vibrations are significantly improved with the additional control circuit.