The Hydro-mechanical Transmission System And Servo Control Of Tractor

The hydro-mechanical transmission system(HMT)divides the input power of the engine into the hydraulic circuit and the mechanical circuit,and has the advantages of high mechanical transmission efficiency,high hydraulic transmission power density,as well as can realize continuous variable speed regulation.In this paper,the research content on speed regulation and servo control of tractor hydro-mechanical transmission system,which is independently researched and developed by the Automotive Engineering Technology Research Institute of Hefei University of Technology,is as follows:(1)Designing the transmission scheme of the tractor HMT transmission system,analyzing the working process of pure hydraulic transmission,hydro-mechanical transmission and pure mechanical transmission.Based on AMEsim,a tractor transmission system model was established and simulated to analyze its principle;(2)According to the change of resistance during the operation of the tractor,analyze the starting and speed regulation process of the tractor.For different working modes,establish different starting control strategy.For the increase and reduce of working resistance,an adjustment control strategy based on engine and hydraulic pump-motor is established to ensure that the tractor maintains the optimal working speed range and improves the tractor's adaptability to variable resistance,and ensure the work quality and efficiency;(3)For the HMT transmission system,the hydraulic pump-motor system has strong nonlinearity,time-varying parameters and external load disturbances.The tracking performance is poor and the oscillation is severe.Based on this the model reference adaptive control is designed for the electro-hydraulic position servo execution system of HMT transmission system,the transfer function model and state equation of the servo system by setting relevant state variables.The simulation results show that the HMT electro-hydraulic position servo control based on model reference adaptive control has good performance.The dynamic response performance can better track the desired output and improve the tracking performance and accuracy of HMT electro-hydraulic servo control.(4)Aiming at the problem that the traditional proportional solenoid valve is greatly affected by the hydraulic power and hydraulic clamping force and spring aging,a new proportional control slide valve driven by micro-motor is designed,and the spool is driven by the micro stepping motor.The proportional adjustment of the spool displacement and the self-locking of the screw can effectively reduce the effects of fatigue failure of return spring,oil contamination and jamming that occur in the conventional proportional solenoid valve.