Study On Driving Speed Control Of Special Hydrostatic Transmission Vehicles

Hydrostatic transmission system can achieve a wide range of stepless speed regulation,with reliable performance,large power ratio,and other significant advantages.It has been widely used in the drive system of medium and heavy vehicles.However,the current research on hydrostatic transmission systems focuses on the matching of dynamic parameters,and the research on speed control is limited.Therefore,this paper takes the hydrostatic transmission speed control system as the research object,focus on structural principles,parameter matching,mathematical model,control strategy and other aspects,and verified by simulation and bench experiments.This essay first introduces the structure type and its application of hydrostatic transmission system.The characteristics of the closed circuits of the three pump-controlled motors are described,and the variable pump-variable motor control loops are selected for key research.Based on the analysis of the characteristics of the engine and hydrostatic system,the variable displacement pump displacement control mechanism and the variable displacement motor variable displacement mechanism control principle,the reasonable parameter matching of engine-hydrostatic system,variable pump-variable motor,hydrostatic system-drive torque was performed and component selection is completed.Meanwhile,the variable mechanism of the pump and motor was established,and the mathematical model of the entire speed regulation system was established.A dynamic simulation model of the system is established on the AMESim software.The characteristics of the output speed,working pressure,flow rate,variable displacement pump and variable motor displacement during the system working process are analyzed.The influencing factors of dynamic performance are simulated and analyzed.The analysis results show that in order to improve the performance of the system,certain control strategies need to be added.A controller based on BP neural network self-adaptive PID was designed.In order to verify the effectiveness of the controller,a speed control system model is built in MATLAB/Simulink software.At the same time,a vehicle model is built and vehicle speed under typical conditions is simulated,and a comparison analysis between ordinary PID control and BP neural network PID control is performed.The simulation results show that the BP neural network PID controller has significant effect on improving the dynamic performance and steady-state accuracy of the system.Finally,an electro-hydraulic proportional variable mechanism test bench for a variable displacement pump is built to verify that the real-time displacement of the variable displacement pump can achieve precise control.The control effect of different controllers is analyzed and the simulation result is verified.