Research On Speed Ratio Control Strategy And Control Method Of All-electrically Regulated Continuously Variable Transmission

Continuously Variable Transmission(CVT)can transmit power continuously and its speed ratio can change continuously which can work with the engine.In a reasonable control strategy,the engine can run in the best conditions,so that the vehicle can play excellent performance.CVT control methods and control strategies are the key to achieving the best performance of CVT.The speed ratio control mechanism of an Electro-Mechanical Continuously Variable Transmission(EM-CVT)is improved on the transmission mechanism,eliminating the hydraulic actuator and the more energy-consuming oil pump,which compared with the hydraulic electronic control mode CVT,greatly improving the economy of the vehicle.The speed ratio control is one of the key of EM-CVT control system.The speed ratio change speed,changes and other factors affect the vehicle economy,power and driving comfort.In this paper,the EM-CVT is taken as the research object and its speed ratio control strategy and speed ratio control method are studied.Firstly,the structure principle and speed ratio adjustment method of EM-CVT are analyzed and the speed ratio control strategies are studied according to the relationship between engine speed,torque,vehicle speed and driving force.Then,based on the analysis of the traditional PID control method and the Fuzzy control method to improve the EM-CVT ratio control method,the PSO is analyzed and the Fuzzy PID controller is established which is optimized by PSO.The mathematical models of EM-CVT,the speed ratio adjustment motor and the engine are analyzed and the models of EM-CVT,engine,speed ratio adjusting motor and vehicle drive system are established by Matlab/Simulink software.The Fuzzy PID controller is used to simulate the vehicle model with the built-in vehicle model.The speed ratio tracking of the vehicle under several common conditions is compared and the effect of speed ratio control is analyzed.The results showed that the PSO-optimized Fuzzy PID controller have prodigious improvement in the control accuracy,response speed and stability.Finally,according to the transmission mechanism of EM-CVT,the EM-CVT test bench and the suitable test method are designed.The results show that the EM-CVT ratio control strategy and the control method are reasonable and correct.