Shift Quality Control Of Automatic Transmission For Off-road Vehicle

Shift quality control is one of the most important key technologies of automatic transmission.This thesis focuses on the modeling of engine and transmission system,modeling and optimization of electro-hydraulic actuator system,trajectory optimization of clutch pressure and throutle opening and clutch pressure control basing on a state observer of hydraulic actuator system to improve the shift quality of high power off-road vehicle.This thesis established the dynamic model of hydraulic automatic transmission containing engine,hydraulic torque conventer,planetary gearbox,clutch and load of the vehicle,analysed the speed and torque characters and proposed the objective evaluation index basing on analytic hierarchy process.The dynamic model of the electro-hydraulic clutch actuator system is established basing on the static pressure-flow characters of the throttle valve and verified by simulation and experimental results.The mechanism of pressure fluctuation problem in the system is analysed by bifurcation theory.An optimization method considering the bifurcation character of the system is proposed.The optimization method is proposed consider the bifurcation boundary as constraint.Simulation and experimental results show that the optimization method proposed in this thesis can improved the dynamic character of the electro-hydraulic system while ensuring the system stable.The trajectory of clutch pressure and throutle are optimized using hp-Legendre-GaussRadau method.A clutch pressure estimator using the output pressure signal or the displacement signal of valve spool basing on Unscented Kalman Filter theory and a sliding mode controller is proposed to ensuring the precise control of clutch pressure.The data of a test vechile is used to estimate the friction coefficient of clutches and verify the proposed dynamic model of the vehicle.The test on a hardware in the loop(Hil)testbench are carried out,which can prove the proposed shift quality control method of this thesis can improve the shift quality of off-road vehicle.