Multi Degrees of Freedom Robust Magnetic Levitation Control of a Flexible Transport Mover with Disturbance Observer and State Feedback Control

Abstract

In this study, a flexible transportation mover, based on magnetic levitation (maglev) principle, which contains hybrid electromagnets and linear induction motors (LIM) is proposed. Magnetic levitation force and inclination torque characteristics of the mover are analyzed using 3D Finite Element Method (FEM). Dynamic models representing multi degrees of freedom (DoF) maglev motion characteristics of the mover are developed by using magnetic equivalent circuit approach in conjunction with FEM analysis results. The mover dynamics shows non-linear characteristics and are unstable from the point view of controllability. In order to address the issue of instability and to precisely control the levitation gap clearance of the mover, a state feedback integral (SFI) controller is designed for each DoF with centralized control approach. The SFI controller design is based on the pole assignment method; the controller poles are determined by applying canonical polynomial of Manabe. The mover includes only optical displacement sensors that measure the gap clearance of the associated magnet poles. Other states required in effective operation of the SFI control are estimated and integrated into the control loop by means of designing disturbance observer (DO). The disturbance observer is capable of estimating external disturbance and as well as parameter uncertainty into a unique total disturbance value. By properly scaling and feedfonvarding this estimated total disturbance value, robust control of the gap clearance is achieved. The performance of the proposed control algorithm is experimentally compared with the I-PD (modified PID) controller. The experimental results have shown effectiveness of the proposed control algorithm even in unbalanced loading conditions for each DoF.