Magnetically Suspended Stepping Motors for Clean Room and Vacuum Environments

To answer the growing needs for super-clean or contact free actuators for uses in clean room, vacuum chamber and space, innovated actuators which have the functions of stepping motors and magnetic bearings in one body have been developed. The rotor of the magnetically suspended stepping motor is suspended exactly like a magnetic bearing and totalled and positioned exactly like a stepper motor. The important trait of the developed motor is that it is not a simple mixture or combination of a stepping motor and a conventional magnetic bearing, but an amalgam of a stepping motor and a magnetic bearing. Owing to optimal design and feed-back control, a toothed stator and rotor are all that are needed structure wise for stable suspension. More than ten types of motor, such as linear type, high accurate rotary type, two-dimensional type and high vacuum type have been built and tested. This paper describes the structure and design of these motors and their performance for such applications as precise positioning rotary table, linear conveyor system and 0-Z positioner for clean room and high vacuum use.