Multi-loop resonant control applied to linear permanent magnet synchronous motors for periodic position tracking

Abstract

This paper addresses the periodic position tracking and load force disturbance rejection in linear permanent magnet synchronous motors (LPMSM). Periodic position tracking is a challenge for LPMSMs, as there are electromagnetic forces that are not uniform along the actuator stroke due to end effects, which can lead to position variations. The proposed control structure combines a proportional–integral (PI) controller in the direct-axis control loop and a modified PI plus a multiple resonant controller (PI-RES) in the quadrature-axis control loop to ensure periodic reference tracking and disturbance rejection. The controller design is carried out by solving a convex optimization problem under linear matrix inequality (LMI) constraints, which guarantee closed-loop stability and transient performance. Simulations and experimental results are performed using a dual quasi-Halbach permanent magnet array linear tubular actuator with a coreless moving armature. The effectiveness of the proposed method is evaluated by applying position reference signals with different frequencies and harmonic compositions in conjunction with two types of load force disturbances. Experiments show the proposed controller results in precise reference tracking with negligible steady-state error.