Novel Strategy for Deriving Torque and Speed Curve of an Electric Bicycle Traction Motor Using Initial Step Analysis

Abstract

In this paper, an initial step analysis (ISA) method was proposed to reduce the calculation time for deriving the torque and speed (TN) curve of an electric bicycle traction motor. The proposed method is based on fnite element analysis (FEA) and can be efectively used in the conceptual design stage, which is the initial design stage. The process of obtaining the TN curve requires repetitive FEA with many steps, which is time consuming. However, ISA utilizes the FEA results conducted by only one step and can drastically reduce the computational cost. The ISA was applied to derive the TN curve of an interior permanent magnet synchronous motor for an electric bicycle traction motor. The results had an acceptable error, and the computation time was reduced by 93.44% compared with result of FEA with sufcient step. To validate the feasibility of the ISA in a practical electric machine, an interior permanent magnet synchronous motor for an electric bicycle traction motor is manufactured, and the average torque according to the current phase angle is tested and compared with the ISA results. The ISA shows an error rate of less than 5% compared with test result. Additional validation of the ISA is conducted on two other test models, and the TN curves was successfully derived with error rate of 3.83% and 0.80%, respectively. Moreover, the calculation time was reduced by 90.24% and 86.99%, respectively. The proposed method can be said as efective and suitable method for deriving TN curves at the early stage of motor design.