Study On Modeling And Control Strategy Simulation Of Vehicle With Continuously Variable Transmission System

Continuously variable transmission (CVT) is the ideal transmission mode for vehicle, and it is one of the important research items of automobile companies and researchers. Now, mental pushing V-belt continuously variable transmission has been applied widely, but it is not mature completely in theory, as well as in practice. Study on matching and control strategy of CVT system of automobile has important theoretical and engineering value. In this paper, theoretical and emulational researches of transmission mechanism and control strategy of CVT system have been carried out profoundly, and the main contents are as follows: 1) The kinematical theory of the metal V-belt type transmission is analyzed. The relation among oil pressure of clamping cylinder, transmission ratio and input torque under load condition is studied and the equilibrium relationship of oil pressure of active cylinder and that of passive cylinder is obtained. 2) Based on experimental data of engine, torque and oil consumption model of engine are established by method of spline interpolation. The optimum economy and power operation line of engine is obtained. To implement optimal economy and power performance of automobile the optimal matching and control strategy between engine and CVT system is discussed, and the target ratio under various running situations is given. 3) The dynamic model of the transmission system including the engine, the clutch, the CVT and load is established, and based on the mathematical model the integrated dynamic simulation system is developed by use of Matlab/Simulink software. Aiming at the evaluating indicator of clutch jointing, a fuzzy control strategy for oil pressure of clutch based on driver's experience is put forward, the fuzzy control algorithm is devised and the fuzzy controller is constructed. The simulation result shows that fuzzy control can reduce friction loss effectively, and meanwhile can decrease impact to engine. 4) To coordinate the power performance and fuel economy performance of automobile with CVT system in dynamic process, the throttle-ratio integrated control strategy that targets expected engine power corresponding to pedal is suggested and the throttle and ratio dual closed-loop control system is constructed. The dynamic performance of automobile is determined primarily by the dynamic characteristic of CVT system, but change rate of ratio determines the dynamic characteristic of CVT. Throttle fuzzy controller and self-adjusting parameter ratio fuzzy controller is designed by use of fuzzy toolbox of Matlab in simulation system, and the control strategy is simulated under complex situations. The simulation result indicates that the integrated control algorithm has good control effect, moreover it is easy to implemented by programming. So the integrated control algorithm is practical and valid and it has guiding significance to software design of TCU (Transmission Control Unit) of automobile with CVT system.