Design and Testing of Single-body 2-DOF Magnetic Levitator for Non-contact Object Transportation

This paper presents the design and testing of a two degree-of-freedom (DOF) magnetic levitator which is capable of controlling the levitational- and lateral-direction forces in a decoupled manner using a single-body actuator. Our 2-DOF levitator is composed of an U-shaped iron-core, an internal permanent magnet (PM), and a pair of actuating coil windings. A 1-inch steel ball is used as a levitated target, and its position is measured in real-time by dual fiber optic sensors. The two perpendicular forces are generated and decoupled by the combination of the PM-biased flux and the coil-driven flux in the common and differential current-excitation modes. We present our control strategy for the decoupled 2-DOF stabilization, and experimentally validate the control performance of our 2-DOF actuator. Using our actuator and the decoupled 2-DOF control, we achieve the significant improvement on the stiffness and the damping of the levitated target in the transportation direction, thereby achieving 82 % reduction in the lateral deviation and 99 % reduction in the settling time as compared to a general 1-DOF magnetic levitation system. Such promising results show a significant potential of our single-body 2-DOF levitator for the high-throughput non-contact object transportation.