Development of a Millimeter-sized Active Magnetic Bearing System

In order to study contact-free levitation systems for micromachines, our group has developed a millimeter-sized active magnetic bearing (AMB) system. The system consists ofa rotor (0.9mm ¢ x6mm, 30 mg), a pair of electromagnets, a pair of photo sensors, and PID controller. Displacements of the rotor are detected by the photo sensors. The rotor and the electromagnets are so small that the rotor in the axial direction is passively stabilized. This paper describes open loop characteristics, closed loop characteristics, follow-up control characteristics to investigate the millimeter-sized AMB system. It is found that the millimeter-sized AMB system makes a velY quick response, because of the small rotor mass of 30 mg. This characterizes the millimeter-sized AMB system.