Closed loop slip control strategy for shifting clutches in hydraulic automatic transmission

For the purpose of engineering development for a new 8 step speed automatic transmission, the shifting process of hydraulic automatic transmission was analyzed, which could be divided into three phases including fill phase, torque phase and speed phase. To ensure smooth and quick shifts, a PID with feed forward control algorithm was generated, through closed loop control based on torque capacity and clutch pressure, to obtain an accurate target slip at clutches. In speed phase, a cooperation method by using torque intervention to engine management system was performed which achieved smooth speed synchronize process. For the convenience of clutch slip calculation, a scheme of clutch position equivalent transfer was also proposed with related calculation of convention factors. Vehicle testing results indicated that with closed loop slip control technology, the torque handover and speed synchronized processes got smoother and faster, which the shift jerk was reduced to an acceptable level. In addition, the benefit of cost saving was noticeable since pressure sensors for shifting clutches would be cancelled by using the introduced proposal.