Noncontact Operation of a Miniature Cycloid Motor by Magnetic Force

Noncontact operation of a cycloid motor by means of a magnetic force has been realized. The fabricated motor has a cycloid reduction system with an internal gear as a stator and an external gear as a rotor. A cylindrical permanent magnet encloses the internal gear. The internal gear generates a wobbling motion due to attractive and repulsive magnetic forces produced by external permanent magnets. An output shaft attached to an external gear is rotated by the wobbling motion of the internal stator gear. This motor can be operated by means of magnetic fields applied to one side of the device. This feature allows the device to be used in medical procedures such as bone distraction osteogenesis, in which the actuator must be inside the human body for a long period of time. Such noncontact operation of the actuator reduces the burden on the patient. The fabricated motor exhibited a maximum torque of 4.1 mN·m and a maximum linear output of 4.9 N using a screw-nut system when the gap between the outer magnets and the motor was 2mm.