Abstract
In the shift process of large-order automatic transmission, jitter phenomenon is common in clutch engagement process, which greatly affects the ride comfort of the vehicle. In this article, the jitter dynamic model of clutch engagement process was established with lumped mass method and virtual displacement principle. Specific to clutch engagement stage, the optimal control of the coordination between driving motor and wet clutch was studied. In accordance with the jitter dynamic model, the state–space equation with controlling variables of motor torque and clutch friction torque was established. In this optimization problem, the torsion angle, torsion angular velocity, and shift jerk are selected as optimization targets. Utilizing the linear quadratic optimal control theory, the optimal trajectory of motor torque and clutch friction torque was obtained. Aiming at the dynamic responses in clutch engagement process, the optimal control in different conditions of weight coefficients, initial torsion angles, and resistance torques was studied. Results showed that the optimal control strategy could obviously reduce the jitter; in addition, the weight coefficient should be determined according to actual situation reasonably.
Highlights
The integration of motor and gearbox is becoming a trend of electric driving system for electric vehicles
With the increase in resistance torque, the jitter appears in motor torque and clutch torque, and shift jerk and friction work increase in some degrees
With the increase in initial torsion angle, the jitter appears in motor torque and clutch torque; shift jerk is increased in some degrees, and the friction work is largely reduced
Summary
The integration of motor and gearbox is becoming a trend of electric driving system for electric vehicles. Keywords Automatic transmission, clutch engagement, dynamic modeling, optimal control, jitter suppression The fluctuations may cause larger shift jerk and dynamic load factor so that the life of transmission part might even be shortened.[18,19] Aiming at the jitter suppression in clutch engagement process, the torsion angle ua = um 2 uc[1] and torsion angular velocity u_a = u_m À u_c1 should be considered in the evaluation criterion.
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