Automotive transmission clutch fill optimal control: An experimental investigation

Clutch to clutch shift control technology, which is the key enabler for a compact and low cost automotive transmission design, is important for both automatic and hybrid transmissions. To ensure a smooth clutch to clutch shift, precise synchronization between the on-coming and off-going clutches is critical. This further requires the on-coming clutch to be filled and ready for engagement at the predetermined time. To optimize this process, the clutch fill was formulated as an optimization problem in our previous work and a customized dynamic programming method was proposed as a solution. Following this idea, this paper presents the clutch fill experimental setup and the optimal control implementation. First, a clutch fill dynamic model, which captures the key dynamics in the clutch fill process, is constructed and analyzed. Second, the customized DP method is implemented to obtain the optimal pressure profile subjected to specified constraints. To validate the proposed method, a transmission clutch fixture has been designed and built in the laboratory. Finally, the experiment is conducted to track the optimal input pressure for clutch fill.