| Hydraulic buffer control modeling of shifting process is one of the key technologies ofautomatic transmission (AT), and it’s the foundation of the shift operation. Taking awheeled heavy-duty off-road vehicle as the platform for the study of high-power automatictransmission in this paper, the vehicular power train dynamics model with the planetarytransmission at the core is established. Starting with the good shift quality for the vehicle,modeling and the characteristic analysis for the shifting clutches and the electro-hydraulicexecution system is proposed. Then the phased hydraulic buffer control model with clutchpressure estimation and sliding mode control theory is formulated for shift quality. Thesuitability of the proposed approach is thoroughly verified by simulation andexperimentation, and measures to further improve shift quality is investigated in finally.The dynamics model of power train for wheeled heavy-duty off-road vehicle isestablished. Following the matching calculation of power train, a detailed analysis for thetransmission gear design and the vehicular launching is carried out by kinematics. Thedynamics unified model for the three degrees of freedom planetary transmission is builtwith the Lagrange’s equations and lumped mass method, and the model validation isproposed. Then the transmission rotating inertia in one gear is calculated, and the12/34shifting process are analyzed and compared by the dynamics unified model. Modelingprovided grounds to hydraulic control modeling of shifting process.Modeling and analysis of buffering for shifting execution system is proposed.Investigation for rotating clutches and brakes is carried out, it is indicated that the balancepiston and the exhaust backfill valve is designed to improve the accuracy of hydraulicbuffering. Then the unified model is built for the shifting clutches, and the effect of linepressure fluctuation on the buffering is analyzed. With the theoretical analysis and datafitting, the second-order model for the hydraulic buffering of the second level controlledvalve system with the exhaust backfill valve is set up, and the duration of filling phase iscalculated.The phased hydraulic buffer control model is designed. The pressure estimation for theshifting clutches is proposed based on the characteristic test of the torque converter, and thecontrol model for the torque phase is designed. Then the system model for the inertia phaseis linearized by Taylor expansion, and the sliding model variable control model is proposed.The shifting process simulation model is set up in the Matlab. Simulation results for gear shifts verify the correctness and the feasibility for the dynamic analysis of the buffer controlmodeling, and the robustness is investigated by simulation in variable operation condition.Finally, with a view to the characteristic of shifting process, the modular designedtransmission control module is developed by function management. Vehicular test shownthat the proposed hydraulic buffer control model is practical, the shift quality and thevehicular power performance is improved by the proposed control model by2to1downshift test particularly. Based on the test data and the objective evaluation indexs, thecharacteristic analysis of shifting process is presented, and the approach for better shiftquality is investigated, then the validated simulation and test is carried out. |
PDF Full Text Request