Near-Zero-Power 2-DOF Noncontact Transportation by Static and Dynamic Disturbance Compensation Using Single-Body PM-Biased Magnetic Levitator

This article presents a 2-degree-of-freedom (DOF) near-zero power control (NZPC) method to significantly reduce the power consumption of a single-body permanent magnet (PM)-biased 2-DOF magnetic levitation actuator for high-throughput noncontact transportation operations. While most of the power reduction methods for the magnetic levitators focus on the compensation of static disturbances such as the target mass uncertainty, control strategies regarding the dynamic disturbance such as the inertial force during the noncontact transportation have been less explored, even though the associated power consumption can be significant for the repetitive transportation tasks. The proposed 2-DOF NZPC method uses 1) the position-controlled loops as the backbone structure, 2) the current-integrating feedback loops to compensate the static disturbances in both DOFs, and 3) the adaptive referencing scheme to compensate the dynamic disturbance. The adaptive referencing method estimates the dynamic equilibrium locus even with an unknown target mass, achieving near-zero power for the noncontact transportation. Using the single-body 2-DOF levitator prototype, we experimentally validate the power reduction performance during high-acceleration noncontact transportation tests with different unknown target mass values. As compared to the case where the identical PM-biased levitator is operated without any compensation method, the proposed 2-DOF NZPC method achieves a maximum of 95% reduction in the accumulated power consumption. The results show a significant potential for industrial applications where high-throughput transportation tasks are required in a noncontact manner.