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Blocking point and sliding area determination In theory, the blocking point is set to be better in the input coupling condition point, and the point change coefficient K=1, which not only ensures the full use of the torque converter's adaptive strength, but also reduces the A sudden change in torque and speed due to latchup. However, from the characteristic curve of the torque converter, it can be seen that the efficiency of the torque converter is reduced from the highest point of efficiency to the coupling point. In order to increase the efficiency of the power transmission system, it is possible to start at the highest efficiency point and increase the pressure of the lock-up clutch but not It will be completely blocked, that is, the lock-up clutch slip control, so that the torque converter only transmits part of the torque, and the other part of the torque is transmitted through the lock-up clutch, which not only improves the transmission efficiency, but also does not reduce the system's ability to resist shock and vibration. The torque converter characteristic curve, as well as the latching clutch sliding area and the latching point, are illustrated.
The torque converter characteristic curve, the sliding zone, and the dash-dotted midline are the curves of torque converter efficiency vs. speed ratio, the two-dot dash line is the change ratio of torque to speed ratio, and the solid line is the torque coefficient. The speed ratio curve and the thick dotted line are the curves of the sliding friction control efficiency and the sliding friction control area and the speed ratio. The highest efficiency point of the torque converter is selected as the starting point X(t0) of the friction control, which not only fully exerts the torque-changing torque-increasing effect of the torque converter, but also avoids the efficiency-decreasing problem after this highest efficiency point. The clutch control pressure is increased until the clutch is fully engaged when the torque ratio K=1. At this time, the engine torque is completely transmitted by the lockup clutch, and the torque converter no longer transmits any torque.
The state equation of the sliding clutch slip control is established. Under the sliding conditions, a part of the engine torque is transmitted through the blocking clutch, and the other part of the torque is transmitted through the torque converter.
State equation linearization process: Since Te, Tc, and control quantity q are all time-varying and non-linear, at the same time, the slippage process time is relatively short. In order to simplify the calculation, linearization is performed. The initial state X(t0) of the start time of the lockup clutch is determined by the rotational speed of the starting point of sliding friction, the control pressure q(t0) (pressure difference between the master and slave side) is taken as 0, and the state (terminal) X(tf) at the time of full engagement. ) Determined by the speed of the blocking point, the control pressure q(tf), t0 is the initial time and tf is the time of the terminal (full lockout). In order to meet the impact degree in the allowable range of conditions, the combined process will produce the minimum frictional friction work.
Calculation and Simulation In order to verify the effectiveness of the optimal control of the lock-up clutch slippage process, we performed a simulation study on the Changan Antelope sedan. Antelope cars and CVT and AT specific parameters such as, 2.
Antelope Sedan Parameters Vehicle Weight (Kg) Engine Model Windward Area A(m2) Tire Radius R(m) Drag Resistance Coefficient Rolling Damping 1190JL472Q2.190.2740.320.018 Power (Kw) Maximum Torque (Nm) Engine Inertia Kg/m2 Vehicle Inertia Kg/ M2 Tire Moment Inertia Main Drive Ratio 49820.190.041.7kg/m24.380 Antelope Sedan AT Transmission Gear One Block Two Block Three Block Four Block Five Block Reverse Block 3.4151.8941.2800.9180.7573.272 Antelope Car CVT Speed ​​Ratio Variation Range: 0.4982.502, gear group transmission ratio: 1.42 initial friction ratio i0 = 0.6, hydraulic torque converter impeller rotation speed x1 = 124.34 / (rad.s-1).
The optimal pressure control simulation model based on MATLAB/Simulink is shown in Fig. 3.
Changan Antelope sedan is equipped with a metal belt type continuously variable transmission and a third gear of an automatic mechanical automatic transmission (AT). The optimal control of the lock-up clutch slippage process is calculated and simulated. For the optimal control pressure (Pa) simulation curve, the optimal control pressure changes smoothly, and the increase rate is firstly reduced and then reduced; and the simulation curves of the angular velocity (radian) variation of the active and driven sides of the lockup clutch during the optimal sliding friction control process, respectively. It can be seen that the speeds of the two are the same when they are blocked; they are the curves of the speed difference (rad) change between the master and the slave; they are the simulation curves of the acceleration (m/S2) of the optimal control process, and the acceleration changes smoothly; Work Rate of Change (Watts) Simulation 1 Change in Impact Velocity (m/s3) during the Sliding-Modification Simulation From the above simulation results, it can be seen that the combined pressure and the main and driven angular velocities are used during the sliding motion from the optimal pressure control to the locking process. The change is smooth and the impact change is also very smooth, and within the allowable range, the sliding friction work during the entire sliding process is relatively small. The optimal control can realize the combined pressure control of the lock-up clutch during AT and CVT.
[Conclusion] The slip clutch slip control is an effective solution to improve the efficiency of the torque converter drive system without causing excessive vibration. The combined pressure control of the sliding friction process has always been a major difficulty that affects its application and promotion. The optimal control method uses the minimum sliding work function as the objective function, the impact degree is within the allowable range, the terminal is constrained, and the terminal time variable establishes a performance functional (Hamilton function) to obtain the optimal control pressure and The time when the latching clutch is fully closed. From the simulation results, the effect is more ideal, and it can be used as a reference for the control of other clutch integration processes in automotive powertrains.
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