Analysis and control of a 6 DOF maglev positioning system with characteristics of end-effects and eddy current damping

Magnetic levitation technology has become the great candidate to provide ultraprecision motion in vacuum environment due to its characteristics, e.g., non-contact, frictionless, and unlimited stroke, etc. This paper presents the design, modeling, analysis, and control of a 6 Degrees-Of-Freedom (DOF) maglev positioning system, and the proposed system is able to achieve a planar motion of 50 mm × 50 mm while the levitation height is up to 4 mm. In this work, the model of eddy current damping for moving Halbach Permanent Magnet (PM) array is analytically established to predict the damping force in operating of the maglev positioning system. Furthermore, the magnetic field end-effect is analyzed in the maglev system, where two guidelines are provided to ideally avoid the model error due to end-effect during the design of the maglev system. To control the maglev positioning system to achieve good planar tracking performance, the system identification is carried out for x and y-axes, and a simple PID controller is designed and optimized according to the specifications characterizing on the closed-loop performance of the maglev system. Finally, the experiments are conducted on the maglev prototype to demonstrate the positioning performance, and the results show that the maximal static positioning error is less than 200 nm with the Root Mean Square Error (RMSE) around 60 nm.