Design and analysts framework for linear permanent-magnet machines

This paper presents a design and analysis framework for the general class of permanent-magnet electric machines. In our analysis, surface-mounted linear motors consisting of permanent magnets and iron-less current carrying coils are treated in a uniform way via the magnetic vector potential. This analysis is developed to design novel linear magnetic levitators for driving precision motion control stages such as those used in wafer steppers, For one such motor structure we give analytical formulae for its magnetic field, force, flux linkage, inductance of the winding, and back electromotive force. We provide experimental results with a six-degree-of-freedom magnetic levitator. These results are in good agreement with analytical estimations. The levitator uses a permanent-magnet Halbach array in order to improve its power efficiency. By analogy, there also exists an electromagnetic dual of the Halbach array. One such dual utilizes a triangular winding pattern in order to achieve a primarily single-sided magnetic field.