A novel design of a rolling rotor actuator with axial air gap

Abstract

The paper presents a new type of actuator consisting of a flat stator, above which a rigid disk-shaped rotor, without windings is placed. Between the rotor and each enabled stator winding, an electromagnetic force is generated, which causes the rotor inclination change in the direction of activated pole. Successive stator winding-switching leads to the change of the contact point position between rotor and stator, which will rotate with an angular speed of frequency-dependent commutation of the stator magnetic windings. In a complete cycle of activation/switching, mobile support point rotates by an angle equal to 2π radians, and the rolling rotor, together with the spindle support, will make a much smaller angular displacement. On the basis of electromagnetic axial forces developed by the stator and friction forces between rotor and stator, the actuator develops relatively large torque at low speeds, up to a few revolutions per minute, without using mechanical gears. The rolling rotor actuator is characterized by constructive simplicity, excellent controllability, long operating life, and it can be used at low speed drives instead of classic motor gears. This paper presents a method to achieve this type of rolling rotor actuator (RRA) with axial gap as well as, operating characteristics reflected in rotor angular velocity as a function of stator angular velocity. The mechanical speed reduction ratio and the starting torque as function of stator angular velocity is also presented.