Cogging torque reduction in permanent-magnet synchronous machines with skew

Abstract

Cogging torque reduction with skewing techniques was explored on the MIT Robotic Cheetah. Skewed machines with either skewed rotors or stators were constructed, tested, and fielded on the robot. Results were compared with a convolution technique for predicting torque waveforms of skewed machines from the torque waveform of the unskewed machine. Fringing fields and axial offsets were investigated as explanations for imperfect torque cancellation. Novel, alternately-shaped magnets were proposed to eliminate these effects, and their efficacy was shown with finite-element analysis.