Abstract
Based on the independently developed five-speed dry dual clutch transmission (DDCT), the paper proposes the torque coordinating control strategy between engine and two clutches, which obtains engine speed and clutch transferred torque in the shifting process, adequately reflecting the driver intention and improving the shifting quality. Five-degree-of-freedom (DOF) shifting dynamics model of DDCT with single intermediate shaft is firstly established according to its physical characteristics. Then the quantitative control objectives of the shifting process are presented. The fuzzy decision of shifting time and the model-based torque coordinating control strategy are proposed and also verified by simulating under different driving intentions in up-/downshifting processes with the DCT model established on the MATLAB/Simulink. Simulation results validate that the shifting control algorithm proposed in this paper can not only meet the shifting quality requirements, but also adapt to the various shifting intentions, having a strong robustness.
Highlights
IntroductionTo improve Automatic Transmissions’ shifting quality, the following measures are usually taken: (1) the timely and effective intervening of engine, namely, the decreasing torque request signal, is given by Transmission Control Unit to Engine Electronic Control Unit in the up- or downshifting process to cut off the fuel injection or delay the response of ignition advance angle, obtaining a reduced torque transmitted by hydraulic torque converter; (2) the switch of hydraulic torque converter’s working state, that is, the hydraulic torque converter, transfers from “locking” state to “unlocking” state to realize hydraulic transmission in the shifting process; (3) the adjusting of engaging pressure, which means actively adjusting the pressure of main oil line in different conditions according to the engine load change to ensure the shifting feel; (4) the working sequence’s match of wet clutch in planetary transmission and brake, avoiding shifting overlapping and power interruption; (5) the adoption of shifting actuator equipped with electromagnetic valve and buffer valve
Goetz et al [4, 5] and Qin et al [6] divided the shifting process into torque phase which is used for the torque switch of dual clutch and inertia phase which is used to realize the synchronization of engine speed and clutch target speed
Based on the DCT dynamics model, fuzzy shifting time decision, and torque coordinating control strategies, the simulation model of shifting control in DCT vehicles is established on MATLAB/Simulink software platform and the upshifting and downshifting process are simulated and analyzed, respectively
Summary
To improve Automatic Transmissions’ shifting quality, the following measures are usually taken: (1) the timely and effective intervening of engine, namely, the decreasing torque request signal, is given by Transmission Control Unit to Engine Electronic Control Unit in the up- or downshifting process to cut off the fuel injection or delay the response of ignition advance angle, obtaining a reduced torque transmitted by hydraulic torque converter; (2) the switch of hydraulic torque converter’s working state, that is, the hydraulic torque converter, transfers from “locking” state to “unlocking” state to realize hydraulic transmission in the shifting process; (3) the adjusting of engaging pressure, which means actively adjusting the pressure of main oil line in different conditions according to the engine load change to ensure the shifting feel; (4) the working sequence’s match of wet clutch in planetary transmission and brake, avoiding shifting overlapping and power interruption; (5) the adoption of shifting actuator equipped with electromagnetic valve and buffer valve. The shifting process completely depends on the switch of dual clutches’ working state and engine torque active control. Guo et al [1] established a two-DOF shifting dynamics model and studied the fuzzy control of DCT shifting process. Considering the inertia, damping, and stiffness of transmission components, Zhang et al established a five-DOF shifting dynamics model [2, 3]. Goetz et al [4, 5] and Qin et al [6] divided the shifting process into torque phase which is used for the torque switch of dual clutch and inertia phase which is used to realize the synchronization of engine speed and clutch target speed. By controlling the throttle opening and the ignition advance angle, the engine speed was actively controlled to accelerate and ease the synchronization
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