Analysis of series-connected varying-lead magnetic lead screws achieving stepwise nut axial speed change under constant screw rotation

In linear transport systems, varying the transport speed according to task demands is important for improving overall efficiency. This study proposes a magnetic lead screw structure that achieves stepwise variation in the nut's axial speed, determined by its position and without the need for active control. The proposed system consists of multiple screw shaft sections with different numbers of thread starts and lead configurations, which are axially connected and driven at a constant rotational speed. A conceptual design is presented, and the effect of thread variation on thrust is evaluated through magnetic field analysis. The results indicate that the thrust transmission remains effective even when the number of thread starts differs between the screw and the nut. Furthermore, dynamic simulations based on a two-mass model confirmed that stepwise changes in linear velocity can be achieved without varying the motor rotational speed.