Bond graphs and transmission output torque control during gearshift: Improved shift quality and reduced calibration effort for automatic transmission control using bond graphs

摘要

Shift control strategies for modern automatic transmissions are usually focused on two tasks: Handover of torque between shift elements and speed control. Additionally a clever design of sequential control and timing is necessary in order to achieve a continuous output torque characteristic and a high shift quality. Current concepts use a high number of application parameters which are optimized for each single shift. Especially for modern concepts with 8 or more gears and therefore between 40 to 100 shift variants the effort for software and application engineers is huge. This report presents a control concept which is based on bond graph modeling and allows a tunable characteristic of output torque during the whole shift. The ZF 8HP70 automatic transmission is used as an example system. For a predefined shift quality target it is possible to calculate requirements for hardware components and engine intervention. In many cases analytical expressions can be found. Within the limits of the transmission and engine components any characteristic between sportive and comfortable can be achieved.