| Summary: | 碩士 === 國立臺北科技大學 === 電機工程研究所 === 103 === To reduce cost and meet the space limitations, the traditional electric assisted bicycle usually uses permanent magnet synchronous motor (PMSM), which is equipped with digital Hall sensor to detect rotor position and driven by six-step current limit controlled method, to provide auxiliary power. Due to the problem of mechanical structure and low resolution of digital Hall sensor, the riders usually feel uncomfortable during the torque coupling period of PMSM and pedals at low speed. Therefore, the control methodology with sinusoidal current controlled method from startup to low speed and vector control at high speed are proposed. It lets the riders be more comfortable at torque coupling period and enhance the torque response capability of PMSM. In order to increase the resolution of rotor position, three linear Hall sensors are carried out instead of digital Hall sensors to drive PMSM by vector control at all operating speed. Hence the performance of electric assisted bicycle is further improved. In order to meet the requirement of continuous speed derailleur for electric assisted bicycle which is driven by PMSM hub motor, the improved rotor position detection method for digital Hall sensor and six-step current control method are developed to enhance the performance of speed control effectively.
To prolong the lifetime of battery, a braking method which consumes the kinetic energy on PMSM under predetermined deceleration speed pattern is derived to avoid overcharging battery. Moreover, a current estimated method by existing motor line current sensors is presented to replace battery current sensor for reducing cost. The experimental results show that the maximal error between measured battery current and proposed method are less than 7.8%.
Finally, a DSP MS320F28035-based motor drive is built to verify the effectiveness of the proposed methods on a PMSM for electric assisted bicycle and wheel hub motor for continuous speed derailleur electric assisted bicycle.
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