Optimal Design of an Axial-Flux Permanent-Magnet Middle Motor Integrated in a Cycloidal Reducer for a Pedal Electric Cycle

Yee-Pien Yang and Jia-Ming Jiang
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Yee-Pien Yang: Department of Mechanical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei 106, Taiwan
Jia-Ming Jiang: Department of Mechanical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei 106, Taiwan

Energies, 2015, vol. 8, issue 12, 1-17

Abstract: This paper proposes an optimal design of a middle motor integrated into a mid-drive unit for pedal electric cycles. This middle motor is an axial-flux permanent magnet brushless DC motor with a stator plate. Facing this plate is a rotor plate that acts as an eccentric component of a cycloidal reducer next to the stator. Both the middle motor and cycloidal reducer are easily installed on the same axle of the bike crankset. In the preliminary design, driving requirements are used to make the middle motor specifications. The numbers of stator slots and magnet poles on the rotor were chosen to achieve the best winding factor, and the winding layout was determined accordingly. A one-dimensional magnetic circuit model of the middle motor was built, and its shape was optimized utilizing a multifunctional optimization system tool. Finally, the resulting design was verified and refined by a finite element analysis. A prototype of the middle motor was fabricated with a stator made of a soft magnetic composite and integrated with a cycloidal reducer. Experimental results show that the motor has a sinusoidal back electromotive force. Additionally, it is easily controlled by sinusoidal currents with acceptable torque and speed curves.

Keywords: pedal electric cycle; axial-flux permanent magnet motor; cycloidal speed reducer; finite element analysis; soft magnetic composite (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2015
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