The application of fast and efficient clutch coordination control in a p2 hybrid automatic transmission

Vehicle acceleration performance and fuel economy two important design goals for transmissions today. P2 hybrid transmissions are designed to optimize the ICE operating points and improve the acceleration performance. In an AT-based P2 hybrid transmission, the gear shift clutches and the engine disconnect clutch are relatively independent in function, but they are closely related to each other in the control process. Slip control of the shift clutches can improve the comfort when the engine is started. Therefore, coordinated control between the two types of clutches is very important. Automatic transmissions are complex systems controlled by hydraulic systems through the connection of planetary gears and clutches. According to the shift logic of the automatic transmission, single step shifts, double step shifts and even multiple step shifts can be realized as simple shifts. That is with a single off-going and a single on-coming clutch. In order to ensure the stability of the closed-loop speed control, only simple shifts are applied in automatic transmissions today. Concerning acceleration performance, for example, multi-step downshifts are often desirable. However, if limited to simple shifts, some multi-step downshifts have to be realized as a sequence of simple shifts, which increases the shift time. Complex shifts are characterized by having more than one off-going and on-coming clutch. It enables fast multi-step shifts and thus is an effective way to improve the performance of a transmission. The effectiveness of the proposed control strategies is verified through vehicle test and the necessary adaptive calibration strategies are discussed as well.