Cogging torque presents problems in high performance brushless DC motor systems. Its presence represents a periodic torque disturbance that degrades the performance of both position and velocity control systems. Moreover, cogging torque can stimulate structural resonances leading to unwanted vibration and acoustic noise. As a result, motor designers utilize numerous techniques to minimize cogging torque [1,2]. For example, it is known that skewing the rotor magnets or the stator slots by one slot pitch ideally eliminates all cogging torque [3,4]. It is also well known that cogging torque is reduced when the number of stator slots is not an integer multiple of the number of magnet poles around the rotor. Likewise shaping the stator teeth and rotor magnets influences the amplitude of the cogging torque.
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