| In recent years,advocating green and low-carbon travel has become the mainstream.Electric power assisted bicycles are welcomed by people all over the world because of their green and convenient characteristics,prompting people to diversify their choices for shortdistance travel.Electric power assisted bicycle is equipped with torque detection device and intelligent power assisted control algorithm,which has great research potential.The research on the power assisted system of electric power assisted bicycle is the key of electric power assisted bicycle,which includes torque detection and power assisted control algorithm.At present,the torque detection of electric power assisted bicycles on the market is mainly divided into two types.One is used the speed sensor to sense the speed,estimate the riding and trampling torque through the algorithm,and then output the power assisted torque.The other is used the torque sensor to identify the riding and trampling torque through the torque sensor,and control the output boost torque through the algorithm.At present,there are some problems in the torque inspection of power assisted bicycle in the market,such as low measurement accuracy and the performance of power assisted system is difficult to meet the use requirements.In the assist control algorithm,the traditional fixed assist ratio is adopted.The assist performance is lack of intelligence and can not well adapt to the riding road conditions.In view of the above problems,the main contents of this thesis are as follows:（1）Design vehicle drive system.The existing electric power assisted bicycle drive system mostly adopts front or rear wheel hub motor drive,which has many disadvantages.The driving system designed in this paper is in a central layout.The output shaft of the driving system coincides with the central shaft of the pedal,which has better performance.n the structural design,the driving relationship of the whole vehicle is analyzed,the appropriate driving motor is selected,the deceleration device is designed,and the driving system is built.The main control chip circuit,motor drive circuit and power supply module circuit are designed in the hardware circuit.（2）Design of torque detection system.Aiming at the problem of insufficient accuracy in the existing torque detection scheme,a central shaft torque sensor based on strain gauge is designed,which is suitable for the central drive system of this design.This paper expounds the working principle of strain torque sensor and the measuring principle of Wheatstone circuit bridge.On the power supply and signal transmission of torque sensor,magnetic coupling resonance wireless transmission is used instead of the traditional conductive slip ring transmission.The circuit principle of wireless transmission module is described in detail.（3）Boost algorithm optimization.Fuzzy control is a rule-based control.It directly adopts language control rules.The starting point is the control experience or the knowledge of relevant experts.The fuzzy control mechanism and strategy are easy to accept and understand,the design is simple and easy to apply.Aiming at the problem that the current assistance algorithm is not intelligent enough,a fuzzy control algorithm is proposed based on the assistance algorithm with fixed assistance ratio to deal with special road conditions and improve the assistance performance.The dynamic model of the whole vehicle riding process is deduced,and the simulation model is built with Matlab / Simulink software to verify the control algorithm of this design.（4）The experimental device and experiment of simulated riding are designed.Combined with the force analysis of the whole vehicle during riding,a simulated riding experimental device is designed.The magnetic particle dynamometer and servo motor are used to simulate the riding resistance and trampling force respectively,and the feasibility of the device is verified by experiments.Simulink simulation verification and experimental device verification are used to verify that the starting performance and slope assistance performance of the designed assistance algorithm are better than the traditional fixed assistance algorithm.Based on the above experiments,the stability and reliability of the power assist system are verified by real vehicle riding. |
