Design and Implementation of Magnetic Levitation Based Modular Omnidirectional Conveyor System

Smart manufacturing is now required to be more intelligent and flexible to support mass customization. Magnetic levitation or maglev technology can increase the flexibility of modern manufacturing with its advantages of low friction and multi-directional motion. Two promising industrial applications of maglev are planar motors and precision stages. This research aims to develop a novel planar maglev system, Magnetic Levitation Floor, and implement it as an omnidirectional conveyor. The contributions of this research are the design and analysis of a novel modular planar electromagnet stator and permanent magnet mover, wrench–current decoupling enhancement using multivariate linear interpolation, and the development of a decoupling strategy for long-range motion. For maglev system development, the planar electromagnet stator is an array of square coil modules. The coil was designed to attain optimal levitation force with efficient power. The support frame has a modular structure for unlimited expansion and flexible layouts. Two planar maglev prototypes, 10-Coil Testbed and Maglev Floor Prototype, were built in addition to the Maglev Floor system for pilot testing. Next, a four-disc magnet mover was designed to achieve six-degrees-of-freedom motion. The magnet layout was optimized with analyses on condition number, maximum current, and power consumption. For real-time levitation control, the cross-coupling effect in the system is decoupled by a wrench–current decoupling matrix. The Lorentz force-based wrench matrices are pre-computed and stored in the lookup table. With discrete lookup data, however, the levitation performance can deteriorate when the mover levitated at pose without data, especially in rotations. In this work, a multivariate linear interpolation was implemented to improve wrench–current decoupling effectiveness between lookup data. For conveying applications, another limitation of the decoupling method using a lookup table is the storage usage which is directly proportional to the data range. To achieve long-range planar motion with efficient use of data storage, the decoupling strategy with small-range lookup data was developed in this work. The lookup data has the range of quarter coil area. The active coil set is selected from the mover location. Then, the wrench matrix is estimated from lookup data and mover pose relative to the active coil set. The feasibility of flexibility enhancement in smart manufacturing using the designed planar maglev system was evaluated through long-range and fine motion experiments. The multivariate linear interpolation significantly improved the levitation performance which suffered from discrete data switching. The decoupling strategy enabled the mover to traverse the levitation area. Experiment results demonstrated the capability of the system for real-world omnidirectional conveying applications

A Novel Wrench–Current Decoupling Strategy to Extend the Use of Small Lookup Data for a Long-Range Maglev Planar Motor

The maglev planar motor is one of the most promising industrial applications. The planar motor can increase flexibility in modern manufacturing with the multidirectional motion of the mover. In levitation control, the decoupling matrix is used to decouple the strong cross-coupling effect. The Lorentz force-based wrench matrices can be precomputed and stored in the lookup table. However, the motion range is restricted by the data range. This paper presents a wrench–current decoupling strategy to extend the use of small lookup data for long-range planar motion. The horizontal data range is 40 mm by 40 mm, which is determined from the minimally repetitive area of the planar coil array. The quadrant symmetry transformation is used to estimate the data for other areas. The experiment results demonstrated the accomplishment of the developed technique for long-range motion with a maximum motion stroke of 380 mm. The disc-magnet movers can levitate with a large air gap of 30 mm and have a total roll and pitch rotation range of 20 degrees

Design of a Compact Planar Magnetic Levitation System with Wrench–Current Decoupling Enhancement

Magnetic levitation technology has promising applications in modern manufacturing, especially for fine-motion stage and long-range omnidirectional planar motors. This paper presents the development of a compact planar maglev prototype with the potential to achieve both applications to increase flexibility for the manufacturing system. The planar stator is designed by using optimized square coils arranged in the zigzag configuration, which provides a better uniform magnetic flux density compared with another configuration. The stator is a compact and portable module with built-in current amplifier units. The single-disc magnet mover is deployed with five controllable degrees of freedom. The cross-coupling effect is decoupled by a precomputed Lorentz force based wrench—current transformation matrix stored in the lookup table. A 2-D linear interpolation is implemented to enhance decoupling effectiveness which is offered via discrete lookup data. Experiments with motion-tracking cameras and a basic controller demonstrate the results of fine step motion of 10 and 20 µm and rotation steps of 0.5 and 1.0 mrad. The potential for multidirectional material handling is represented by a total horizontal translation range of 20 mm by 20 mm with a maximum air gap of 26 mm and a total rotation range of 20 degrees for both roll and pitch