Analysis of Magnetic Field and Evaluation of Mechanical Time Constants on a Linear DC Motor

A linear dc motor (LDM) is useful in a high-speed, high-accuracy positioning system with a feedback controller [1]. A moving-coil-type LDM can be used for a pen recorder. We analyzed the magnetic field of an LDM, using a 3D finite element method, and designed an improved LDM with the specific intention of increasing the flux density in the gap. The mechanical time constant is the most basic parameter in the positioning control system. We calculated the mechanical time constants of the LDM at various frequencies, and clarified the effect on the mechanical time constants of an increased flux density in the gap of the improved LDM.