Research On Electromagnetic Characteristic Of Permanent Magnet-inductor Magnetic Lead Screw

Linear machine or rotating machine with mechanical lead screw is often adopted to realize linear motion. However, the density of thrust force produced by linear machine is quite low, and the mechanical lead screw has the feature of low motion precision and poor reliability. In recent years, a new kind of lead screw—magnetic lead screw(MLS) is proposed, which makes the direct mechanical contact between screw and nut replaced by the magnetic coupling, and can realize the transmission of power without mechanical contact. It can solve the problem of low motion precision and poor reliability of mechanical lead screw fundamentally, and can produce high density of thrust force with rotating machine. Therefore, the MLS has a wide application prospect in the linear motion system.The main study object of this paper is permanent magnet(PM)、inductor and PM-Inductor MLS. The PM MLS’s structure and the mechanism of thrust force are introduced firstly, and the relation between turust force and torque is revealed. 3-Dimensional(3D) finite element method(FEM) is adopted to study magnetic fields’ distribution characteristic and thrust force-displacement characteristic of PM MLS. Based on it, the equivlent structure of thrust force and torque is proposed, and the equivlent 2-D FEM model for calculating thrust force of PM MLS is set up, which is proved correct. The effect of geometric parameters on thrust force is analysised in detail using the equivlent 2-D FEM model, which offers advices for the design and optimization of PM MLS.According to the fact that the thrust force of PM MLS can’t be regulated when the relative position of mover and rotot is fixed, the inductor MLS is proposed, whose mover is excitated by excitation winding. The equivlent 2D FEM model is adopted to calculate the distribution of airgap magnetic fields and the thrust force-displacement characteristic. The relation between electromagnetic thrust force and excitation magnetic force is analysised. The study shows that the geometric parameters of tooth and slot has a great influence on airgap magnetic field distribution and electromagnetic thrust force.Combining the features of PM and inductor MLS, the PM-Inductor MLS is proposed, whose mover is excitated by excitation winding and PM. The airgap magnetic fields distribution and thrust-force characteristic are calculated by suing 2-D FEM. The relation between PM and electromagnetic thrust force is analysised and the regulation characterisitic of thrust force is revealed. The study shows that the regulation characterisitic has a close relation with the direction of thrust force and excitation current and the position of permanent magnet poles.