Design Of Bicycle Power Assisted System

In recent years,people pay more and more attention to safe travel and environment-friendly travel,and the use of electric bicycles is also increasing.The traditional pure electric bicycle speed is controlled by the handlebar speed control system based on open-loop control,safety and comfort are deficiencies,and electric power-assisted bicycle through the power-assisted system to detect foot-riding force size,To control the output of the assistive motor,in order to help the motor to help the riding state of intelligence.As the core of power-assisted bicycle,power-assisted system is the key to researching the power-assisted bicycle.The power-assisted system mainly includes torque sensor system and power-assisted motor control system.Common torque sensor design solutions for torque displacement conversion,strain gauge detection method and the use of inverse magnetostrictive effect.The design of the assist motor control system includes the design of the main control circuit and the realization of the motor control algorithm.The main contents of this paper are as follows:(1)In the aspect of torque sensor design,firstly,several kinds of torque sensors in domestic and overseas market are researched and compared,a design scheme of crank torque sensor system based on strain gauge detection is proposed,and then the mechanical model of crankshaft and the mechanical structure of new crankshaft,Finally completed the torque sensor circuit design.Crank torque sensor mainly by strain gauge full bridge,AD623 instrumentation amplifier and crank mechanical structure and other components.In order to improve the accuracy and stability of the crank torque sensor signal,the Kalman filter is used to filter the collected torque signal.(2)In assisting the motor control system design,the design of the main control circuit,the motor drive circuit and the power detection circuit are completed first,and then the system software and algorithm design are completed.Using TMS32f28027 models 32-bit DSP processor as the master chip,BLDCM is used as a booster motor,and then the back-EMF method is used to detect the rotor position of the booster motor.The vector control algorithm is used to control the motor torque.(3)Finally,the entire power assisted system test is completed.The test includes the construction of the experimental platform,the testing of the power supply test circuit,the stress test of the new crankshaft,the performance test of the crank torque sensor and the output test of the assist motor.The experimental results show that the power assisted system is stable and can measure pedaling force with high precision,which can assist electric bicycle.