Research On The Fuzzy-PI Composite Speed Ratio Control System For Metal V-belt Continuously Variable Transmission And Performance Assessment Of Vehicle Equipped CVT

With the booming of the vehicle industry, designing the modern vehicle which is safer, green, more comfortable and lower emission could suit the request of the developing age. The technique of continuously variable transmission (CVT) on vehicle can lighten the driver's intensity of work, enhance the security, the comfort and the emission of driving, let the vehicle staying in the state of good performance and it is the perfect transmission on vehicle. Metal V-belt continuously variable transmission with the characteristics of higher capacity of power transferred, higher transfer efficiency and longer life is the most widely used CVT of the world.Metal V-belt CVT depends on the metal pieces to transfer the torque, changes the working radius of the metal V-belt on the master pulley shaft and the slave pulley shaft continuously to achieve the continuous changes of the speed ratio. It can control the working point of the engine effectively and realize the best match between the engine and the gearbox. It enhances the power and economy of the vehicle.At first, the paper introduces the basic structure and the working principle of CVT, especially about the key controlling techniques.Then pertaining to the non-linear and time-varying characters of metal v-belt CVT on vehicle, the paper designs the Fuzzy-PI composite speed ratio control system. It not only makes good use of the fuzzy controller in adapting the non-linear and time-varying characters of the target under control and strong robustness, but also takes advantage of the PI controller in eliminating the steady error and enhancing control accuracy. The paper also compares the Fuzzy-PI control with the classical PID control and approves the advantage of the Fuzzy-PI control.With the dynamics analysis of the drivetrain of CVT, using one domestic designed vehicle as the research object, the paper establishes the platform of simulation of vehicle equipped CVT which contains the modules of engine, hydraulic torque converter with a locked clutch, drivetrain, driver and speed ratio control using Matlab/Simulink. On the basis of the model of vehicle equipped CVT, the paper also designs the model of the power and economy assessment. With the method of simulation, it is found that the Fuzzy-PI composite speed ratio control can track the target speed ratio well, it has a good dynamic response and high control accuracy of steady state, and it also approves that the power and economy of the vehicle is enhanced with equipping CVT. At last, the paper introduces the bench test and dynamic test of CVT. With the test data, it approves the feasibility of the Fuzzy-PI composite speed ratio control.