Optimal design of a magnetization fixture for cogging torque reduction of ODD spindle motor

Cogging torque results from the interaction of the rotor magnets acting on the stator teeth or poles independent of any current. It is desirable to reduce the cogging torque since it may cause speed ripple and vibration, particularly at light load and low speed. When the motor equipped ring magnet, it is very effective to reduce the cogging torque as changing only the magnetization patterns of the permanent magnet in the same motor structure. In this paper, optimum shape of magnetizing fixture resulting cogging torque reduction is investigated by using the finite element method (FEM), design of experiment (DOE) and response surface method (RSM).