Design Of The Electric Bicycle Controller Based On MCU ATmega48

The electric bicycle is wildly used by people for its flexibility, portablity, energy saving, environmental protection, affordable price, and has become an ideal vehicle for short trip. The electric bicycle industry has a broad prospect in our country, so developing the electric bicycle has good social significance and congsiderable economic benefits .Brushless DC Motor(BLDCM) is the main driving source of the electric bicycle, and the electic bicycle controller is the control core of the electric bicycle as a key component, constituting the driving system with BLDCM. In order to improve the riding comfort and safty of the electric bicycle, this paper carrys out an in-deepth research on its driving system, and gives a brief introduction to the functions of the electric bicycle controller and its software and hardware design.Firstly, the basic structure and principle of BLDCM are briefly introduced and its mathematical model is sought. The reasons for commutation torque ripple of BLDCM are detailedly analyszed, and a way of Delay on-overlap-phase mothod is put forward to suppress the torque ripple. Simultaneously, based on the analysis of energy regenerative baking priciple of BLDCM, the control law is proposed. At last, the funtions of electric bicycle are put in.Secondly, the control strategy of the driving system is presented in detail. According to the speed characteristics of BLDCM, the speed of BLDCM is adjusted by regulating the armature voltage with PWM, and the double close-loop systems of current and speed are discussed. The adoption of fuzzy-PI control algorim in the speed regulator implemnts the control accuracy of the speed effectively.Finally, the software and hardware design of the electric bicycle controller is introduced, and the experimental results of the prototype are note. The hardware design focuses on the MCU ATmega48, including the power circuit, three-phase full-bridge inverter and its driving and protection circuit, current detection circuit and so on. The software is designed with modular structure and an time-shared idea of"time slice". The module procedures are programmed according to control demands, such as driving and commutation, flexible electric baking(EABS) and under-voltage protection, and the double close-loop systems of speed and current are achieved. Ulteriorly, the flow chart of each module is listed.The experimental results indicate that the controller designed in this paper controls BLDCM well, and each performance is scheduled to requirements. the motor has a good performance with quick start, small torque ripple, good speed tracking and smooth and reliable operation.