| Continuously Variable Transmission(CVT)has the characteristics of compact structure,good smoothness,comfort and excellent fuel economy,and is regarded as an ideal vehicle power Transmission device.CVT can rapidly and continuously change the speed ratio according to the driver's intention and vehicle driving feedback information,so as to make the engine work in the best working range and improve the fuel economy and power performance of the vehicle.As one of the most widely used CVT,metal belt CVT has a bright future in the research and application of automotive power transmission.As an important part of metal belt CVT,electro-hydraulic control system is mainly composed of hydraulic control system and dynamic control system.The performance of the electro-hydraulic control system not only determines the performance of the metal belt CVT,but also affects the power performance and fuel economy of the vehicle.In order to improve the contradiction between CVT power performance and economy and improve the design method of hydraulic control system,it is particularly important to study the hydraulic control system and control algorithm.In this paper,the metal band CVT hydraulic system and its dynamic control system are studied in depth,and real-time simulation and verification analysis are carried out on the ring test platform with hardware.The main research contents of this paper are as follows:(1)Design of hydraulic control system of metal belt type CVT.The existing design methods of hydraulic control system are analyzed,and the parameter matching design method of hydraulic control system is determined.Based on the function requirement of hydraulic control system and single loop hydraulic system,the parameters of clamping force and speed ratio control system and hydraulic torque converter locking control system were matched.(2)Establishment of metal belt CVT system model.Based on the original characteristics of engine and hydraulic torque converter and the theory of metal belt CVT transmission,the mathematical models of engine,hydraulic torque converter and stepless transmission mechanism are established.At the same time,the mathematical model of hydraulic solenoid valve,oil pump and hydraulic cylinder was established on the theoretical basis of parameter matching of hydraulic control system.AMESim software was used to build the model of hydraulic control valve and analyze its working characteristics.(3)Control algorithm research and simulation analysis.Based on the model of metal belt CVT system and the requirement of control system,the PID controller of speed ratio and clamping force tracking is designed.Aiming at the existing locking law of the hydraulic torque converter,a method of identifying the locking point of the hydraulic torque converter based on the driving intention was proposed,and the locking control of the clutch was studied by combining the slip control,and a slip control algorithm based on the driving intention was designed.AMESim and MATLAB/Simulink co-simulation were used to verify and analyze the rationality of the hydraulic control system and control algorithm.(4)Metal band CVT electro-hydraulic control system hardware in the loop ring verification.On the basis of fully understanding the principle of the hardware in the ring test platform,the hardware in the ring test system based on NI-PXI is used to verify the hardware in the loop of the metal band CVT electro-hydraulic control system.The effectiveness and real time of the hydraulic control system and the control algorithm designed in this paper are analyzed to provide experimental research basis for the development of electro-hydraulic control system. |
PDF Full Text Request