Study on the Electric-Bike Control System Based on the Microcontroller ABSTRACT In recent years, the waste gas from the gasoline-automobiles has caused severe pollution problems in cities. So, it's more and more important to develop the so called "green-automobiles". Considering our country's status, to develop the electric-bike will be helpful to solve the pollution problem. With the virtues of flexibility, slimness and zero waste-gas, electro-bike is more and more popular. By enhancing the driving-motor technology and power devices technology, the control system developed quickly. But nowadays, most of the electric-bicycle products in the markets adapt low-integration degree devices in their control system. The problem is that the function of these devices is too simple to fully utilize the system's potential and to solve some specific but meaningful control questions. In this project, ATmega8 an MCU product of ATMEL company has been used. The consideration between low-cost and good-controlling performance has been well balanced by choosing this central-controlling unit. The following works have been presented in this project. Firstly, the characteristic of the system's driving source-the Brushless-DC-Motor has been analyzed based on the mathematical model. Furthermore, the controlling strategy has been designed in detail based on the characteristic of MCU. This part includes the following works. The current is measured indirectly by using a shunt- resistor. In order to guarantee the velocity modulation's precision and quick-response, a double closed-loop control for current and velocity has been adopted and the control strategy is realized by the software using PI algorithm. To the measurement of the velocity, a hardware-softening method has been adopted and the motor's soft-starting method has been designed. In order to drive the MOSEFET full-bridge rectifying circuit, the high-performance driving-IC IR2131S has been used and PWM driving strategy has been adopted. The PWM wave's controlling and the system protection issues are integrated into the central controlling unit. This helps to increase the reliability of the whole system. III
At the last, the whole system's hardware and software have been designed based on the system's control strategy and the reliable-designing question has been discussed in the paper. From the work which has been done in this project, the conclusion can be draw that the electric-bike control system based on the MCU has the virtues of high-performance, high-reliability and easy to further developing. This paper presented an experimental base for the futher research。 KEY WORDS: Microcontroller Control system Brushless-DC-Motor III