Design Of Wheel Motor And Research On Its Characteristics For Electric Bicycle

In the 21st century, climate warming and energy crisis have become the common challenges for humans. Researching the electric bicycle (EB) which has the advantages of energy saving and environmental protection become an important way to solve these problems. The wheel motor is the core of EB, and its performances are decisive factors for realizing the function of EB. At present, wheel motor has the disadvantages of high loss, performance instability and low efficiency. Researching a wheel type permanent magnet synchronous motor (WPMSM) which has the advantages of high control accuracy, reliable structure, good stability and high efficiency has important significance.In order to determine the overall scheme of wheel motor, firstly, analyzed the requirements of wheel motor for electric bicycle. Calculated the kinetic and dynamic parameters of wheel motor; determined the driving force and output torque of wheel motor. Then, by analyzing motor constant and choosing relevant parameters, calculated the main dimensions of wheel motor, and then, determined general mechanical scheme. Further, introduced the concept of unit motor; compared the different winding and pole tooth slot scheme, and determined general electromagnetic scheme of wheel motor.By using JMAG software, finite element analysis for the air-gap magnetic field of wheel motor was carried out, determined reasonable air gap length, and optimized the air-gap flux density wave. Through analyzing the armature magnetic dense, output torque and efficiency, the tooth width and yoke high of motor stator armature were optimized, and determined the width and thickness of permanent magnet structure parameters by the same design optimization method. Considering comprehensively the permanent magnetism materials performance and cost of magnetization, chose magnetic higher NdFeB materials and parallel magnetization way. And then, finite element analysis for the no-load back EMF of wheel motor was carried out. The superposition principle of back EMF waveform and the harmonic frequency which had great influence on waveform sine were got. Further, calculated the iron and copper loss; got the optimal design efficiency of wheel motor.Aimed at the cogging torque of the wheel motor, further optimization of torque characteristics was made. Establish the analytical model of cogging torque. Through analyzing the analytical model, got the method to weaken cogging torque, and analyzed the influence of different electromagnetic scheme to cogging torque. Based on the MATLAB/Simulink, build the simulation platform of wheel motor. Using the simulation analysis to get the start-up characteristics includes the response characteristics of peed, torque and three-phase currents. According to the optimized mechanical and electromagnetic scheme, wheel motor prototype was processed. The back EMF, torque, temperature rise and efficiency of the prototype were systematically tested. Test results showed that the speed range, response characteristic, torque output and overload ability of prototype all met the design requirements. The efficiency of prototype reached 88.9%, its comprehensive performance was better than ordinary brushless dc motor, and verified the rationality of the design schemes in the subject.