CVT Fuel Economy Optimization Based On Slip Ratio Control Strategy

This paper aims to improve the fuel economy of CVT.Starting from engine matching and control optimization,optimization strategies are put forward.Computer simulation and hardware in the loop simulation are carried out.The theoretical and experimental combined method is used to build mathematical modeling.Optimization objective and optimization algorithm are proposed.The iterative algorithm is used to solve the transmission efficiency of the system.New target ratio model and target throttle opening model are obtained after data processing of the results.The new speed ratio control strategy is determined.The speed ratio controller model is established in MATLAB/Simulink.CVT transmission mechanism is studied,and the basic movement of CVT is analyzed.The static force analysis and theoretical calculation of the key parts in CVT is conducted.The dynamic force distribution is researched based on CVT motion analysis and force analysis.The power loss from CVT transmitting torque is researched,including mechanical transmission and hydraulic system loss.Measures are put forward to optimize the efficiency of CVT.The traditional clamping force control theory is researched.Slip ratio is defined and its influence of CVT are analyzed,with the proposal of two different slip ratio control strategies.The clamping force controller is designed in MATLAB/Simulink based on the two strategies.Co-simulation model is established.The simulation results show that the slip ratio control strategy with the best matching coefficient of friction can ensure the robustness of the system under the premise of improving the transmission efficiency.Slip ratio control strategy and traditional control strategy are compared after the overall optimization scheme determined,which shows that the slip rate control strategy can improve the transmission efficiency;lower torque and higher speed ratio make the improvement of efficiency more significant.Fuel consumption model is established to evaluate the overall optimization effect.The simulation results show that the fuel consumption can be reduced by 5%~10% on the original basis.The dSPACE hardware in the loop simulation platform is established,including modeling in MATLAB/Simulink environment,compiling and downloading C code with RTW Build,controller designing,related wiring and parameter settings and so on.The loop simulation test is conducted based on ECE+EUDC.Test results show that the controller with the optimization of clamping force and ratio can meet the requirements to reduce vehicle fuel consumption;the control effect of the real controller has a certain gap compared to the virtual controller and needs further improvement.