Fractional-order feedforward control method for permanent magnet linear synchronous motor based on frequency-domain adjustment theory

Abstract

For a permanent magnet linear synchronous motor motion system, following error is one of the key indexes used when the motion system is applied to high-performance manufacturing equipment. Owing to the uncomplete description of the motion system’s control frequency-domain characteristics, the integer-order feedforward control method adapted for a two-degree-of-freedom feedforward-feedback control system may result in large-trajectory following error. To address this problem, this paper proposes a fractional-order feedforward control method with the frequency-domain characteristics adjustment ability. For the proposed method, this paper constructs an equal-order fractional-order compensator to compensate the frequency-domain errors of the integer-order feedforward control method. According to the features of the equal-order fractional-order compensator, this paper decomposes the compensator into multiple independent units, clarifies the relationship between parameter selection and frequency-domain characteristics, and establishes an optimal solution formula for phase error minimization. Through compensator decomposition and optimal parameter determination, the proposed fractional-order feedforward control method can accurately describe the control frequency-domain characteristics of the motion system. The simulation experiment results show that the proposed method can effectively reduce the gain and phase errors. The physical experiments were conducted on a motion system constructed by permanent magnet linear synchronous motors. And the experiment results are presented herein to validate the effectiveness and advancements of the proposed method in high-precision motion control for the permanent magnet linear synchronous motor motion system.