Perfect Tracking Control of Nonminimum Phase Systems in Magnetic Levitation System

Feng LI  Jianming LU  Xueqin ZHAO  Takashi YAHAGI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A    No.5    pp.1437-1445
Publication Date: 2006/05/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.5.1437
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Systems and Control
tracking control,  nonminimum phase system,  multirate control,  

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In this paper, we study the problem of perfect tracking control of nonminimum phase systems in magnetic levitation system. Generally, perfect tracking control schemes cannot be applied to nonminimum phase plants because of unstable pole-zero cancellations. Although the method of state matching using multirate feedforward control to realize perfect tracking control have been proposed, the oscillation restraint and the feasibility in nonminimum phase system cannot be satisfied at same time. We propose a method using the difference of state variables to generate a smooth desired state variable trajectory in the discrete-time systems. The techniques we proposed are applicable to nonminimum phase discrete-time systems and the oscillations between the sampling points are well restrained. We will show that the structure of the proposed perfect tracking controller is very simple and clear. Finally, computer simulations and experiment results based on magnetic levitation apparatus are presented.