Investigation on Pressure Control of Shifting Clutch for High-power Automatic Transmission

In order to improve the control level of oil pressure which regulates the performance of shifting clutch (including wet brake and wet clutch) for high-power automatic transmission and to improve the shift quality of vehicles, the balance piston was designed to balance the centrifugal effect for the rotating clutches, and the exhaust backfill valve was also designed for the oil discharge loop to eliminate the uncertainty caused by air in the piston cavity. The low pressure can keep the shifting clutches free of air due to the exhaust backfill valve. The shift execution system of the testing automatic transmission was analyzed, and the model calculation was administered for the piston motion, the electro-hydraulic pressure regulation and the slipping process of the shifting clutch. And the pressure regulating of inertia phase during the gear shift is characterized as a one-order control based on the end of the torque phase. Combined with phased parameter calibration, the sliding mode control was presented to overcome the external disturbance and parametric uncertainties. Simulation analysis for the effectiveness of control strategy was conducted on the basis of MATLAB. The power-on 1st-2nd up-shift with B2 brake oil-charging and the power-on 3th-4th up-shift with C2 clutch oil-charging test were considered respectively. The simulation curves show that the duration time, the shift jerk and the wear power loss of the inertia phase are effectively controlled within a reasonable range. Finally, the proposed control strategy is thoroughly verified on a heavy-duty off-road vehicle equipped with a high-power automatic transmission, and the good shifting quality has been achieved in the inertia phase which is demonstrated by the experimented data.