Analysis of double side ironless permanent magnet linear synchronous machine with low normal force

An electromagnetic linear machine is an energy conversion device that can convert electrical energy into linear motion. Conventional study of electromagnetic linear machines mainly focuses on the axial thrust, because it can be used to act on external payloads directly. However, due to manufacturing error and mechanical deformation of mover, the double side permanent magnet linear synchronous machine (DPMLSM) often generates unbalanced normal force on mover. This unwanted force may aggravate the mover deformation and lead to unequal airgap, which increases the normal force further, consequently leading an increase of friction, vibration and noise of the system. Therefore, the normal force in also important that is ignored. The purpose of this article is to study the normal force of DPMLSM to provide theoretical support for the design. The normal force of DPMLSM is analysed systematically and the magnetic field distribution is formulated analytically. The normal force for different mover deformation and different number of Halbach segments are analysed. It is found that the offset of normal installation has a significant impact on the normal force, and the more segments there are, the smaller the normal force. The width of the pole is optimized and an experimental prototype is fabricated to verify the accuracy of analytical and numerical calculations through experiments.