Influence of non-coaxial alignment on interaction forces for the contactless magnetic driver of a reciprocating motion

Abstract

Using interaction forces between two magnetic sleeves, the contactless magnetic driver changes the rotating motion of a motor into reciprocating motion by a link mechanism. In an ideal state, the two sleeves of the driver are coaxial, but due to manufacturing and/or assembly errors, the real working state is non-coaxial. The air gap and consequently the magneticfield and interaction forces are altered. Therefore, it is very important to predict the changing of interaction force for some application. Assuming that the magnetizations are rigid and uniform, a mathematical model of the interaction force between two axial magnetized sleeves is developed based on the theory of equivalent magnetic charges. The model considers two magnetic sleeves at any relative position and attitude, and is verified experimentally for the two sleeves being coaxial. A numerical solution is implemented to compare interaction forces at the coaxial and non-coaxial states. Through numerical prediction, eccentricity between the sleeves of 0.5 mm generates a radial force approximately 70 N. The modeling method is also applicable to cuboidal magnets.