A Small Axial-Flux Vernier Machine With Ring-Type Magnets for the Auto-Focusing Lens Drive System

A small axial-flux permanent magnet vernier motor (PMVM) is investigated to satisfy the requirements of high drive torque, low speed, low noise, and low-power consumption for application in the camera auto-focusing lens drive. The proposed axial-flux PMVM is constructed with ring-type magnets in the rotor and has strict dimensional constraints due to its location in the lens barrel. The design approach is an alternative motor design method coupled with the analytical method or the finite-element method. The proposed motor's electromagnetic performance was verified by means of both methods. Finally, a prototype was built and tested, showing an adequate range of speed while also meeting the noise limits, and consuming less than 2 W of power.