Axial Gap Self-Bearing Motor with Four Concentrated Stator Coils

Abstract

This paper proposes a novel structure of an axial gap self-bearing motor. The axial gap self-bearing motor controls both axial force and motor torque by using the similar structure of a disc motor, then the structure and control system can be simplified. In this paper, for further simplifying the structure, the number of the stator coil is reduced to four for one side stator for a 4-pole disc rotor. One side stator produces only 4-pole magnetic flux, then the whole of the stator coils can be connected in series and driven by the single amplifier. Two stators are required to produce continuous motor torque and the bidirectional axial force, then the drive system can be composed of eight concentrated coils and two power amplifiers. To obtain continuous motor torque, the permanent magnets are attached to the rotor to have 45 degrees phase difference between two sides of the disc. In this paper, the axial force and motor torque of the proposed structure are analyzed theoretically, and the control method of the axial force and motor torque are derived. Experimental results show that the proposed motor can control the axial position and the rotation speed simultaneously.