The Full Power Shift Control System Design Of The Hydro-Mechanical Continuously Variable Transmission

Hydro-mechanical continuously variable transmission is a kind of double-flow compound transmission.It not only maintains the advantages of high power and high transmission efficiency of mechanical transmission,but also inherits the characteristics of hydraulic transmission variable transmission.Therefore,it is widely used in engineering machinery and agricultural machinery.It is the key to ensure the continuous speed ratio of variable transmission of hydraulic machinery to formulate a reasonable control strategy.Full-power shift method regulates the displacement current during the overlapping working time of hydraulic machinery clutch,completes the exchange of high and low pressure side pressure in closed hydraulic circuit,and the continuous change of speed ratio and the uninterrupted power output are ensured in the process of changing stages.In this paper,the design and hardware-in-the-loop simulation of hydro-mechanical continuously variable transmission full-power shift control system were carried out.The main contents are as follows:(1)Aiming at the problem that the pressure theoretical prediction model of the target stage of the hydro-mechanical continuously variable transmission is complex in form and computationally heavy,which cannot be applied by the control system.The global sensitivity analysis method was used to screen the low-sensitivity parameters in the model,and the target stage pressure calculation model was obtained according to the screening results.The prediction model shows that the average error of hydraulic stage pressure prediction value is 4.5%,and the average error of hydro-mechanical stage pressure prediction value is 5.3%.(2)Taking MATLAB/Simulink as software development environment and Rapid-ECU as hardware platform of control system,based on the method of full-power shift method,the control strategy of hydro-mechanical continuously variable transmission full-power shift was designed and the simulation model was built.The computer simulation of the process of shift was implemented under selected working conditions.The results show that the control strategy can correctly output control signals according to the input state parameters to make the pressure in the hydraulic circuit exchanges and realize the full power shift.(3)Based on the xPC dual-computer real-time simulation system,the hardware-in-the-loop simulation model of the control system and the application model of the target machine were established.The hardware-in-the-loop simulation test platform for the full power shift control system of hydro-mechanical continuously variable transmission was built.The hardware-in-the-loop simulation test of hydro-mechanical continuously variable transmission full power shift control system was completed under the same conditions of computer simulation.The results show that the average error of displacement current control signal in target stage is 1.4%;the average error of pressure test value in target stage is 1.6%;the average error of overlap time of clutch control signal is 2%.The function and control effect of the control system basically meet the demand.