The system structure with control algorithm of motor drive for an electric bicycle based on a BLDC motor drive is shown in Fig. 1. It consists of a dsPIC30F4011 microcontroller, protection circuit, optical coupling isolation, inverter, current sensor, encoder, and communication interface. The microcontroller dsPIC 30F4011 manufactured by Microchip technology incorporate is the core controller of the electric bicycle. It is a 16-bit CPU with the capability of digital signal processing. Moreover, it supports many powerful modules such as built-in PWM module, addressable encoder interface module, and input capture module, these make the design friendly and thus shorten the development schedule. The three-phase bridge inverter comprises six power MOSFETs for switching as shown in Fig. 2. The photocoupler TLP250 manufactured by Toshiba semiconductor company, is used for electrical isolation between the microcontroller system and bus voltage. The motor currents from the DC bus are sensed through the current detection circuit. The magnet pole and rotor position are detected by the Hall effect sensor. In such a way, the speed and rotor position can be calculated and precisely controlled, subsequently. The 120-degree conduction of pulse width modulation technique for MOSFETs switching, is applied to drive the thee-phase inverter.
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