1992 Volume 112 Issue 11 Pages 1080-1086
A linear pulse motor (LPM) has many advantages for high accuracy positioning actuator, because it has linear motion without any mechanical link. The flat type LPM is generally used in many industrial applications. It has, however, a disadvantage that the mover support mechanism becomes complex and heavy, because the attraction force between the stator and the mover is very large. As the attraction force is balanced in the cylindrical structure, the cylindrical LPM is allowed to have the simple and light weight support mechanism.
The inset magnet type cylindrical LPM, which has a permanent magnet between A-phase and B-phase stator, has merits as a simple shape of magnet and a reduction of the motor diameter. It has a weak point that thrust unbalance occurs because the magnetic flux pass of the outer poles is longer than that of the inner poles. The thrust unbalance decreases the pull-in thrust force and increases the positioning error.
In this paper, two practical methods are proposed to improve the thrust unbalance. The one is the exciting current adjustment and the other is the method with compensation permanent magnet. These effects are examined with theoretical and experimental results.