College of Engineering – Control Seminar Series

In automatic transmissions, an open torque converter transmits torque from the engine to the transmission using fluid coupling. Although torque converters are ideal launch devices for automatic transmissions, they are inefficient in steady-state operations. An electronically controlled torque converter clutch is often implemented to control the slip between the pump and turbine of the torque converter, thereby increasing its energy transfer efficiency and increasing vehicle fuel economy. Even though reducing torque converter slip minimizes losses due to fluid coupling, it also decreases the damping provided by a slipping torque converter and as a result increases the sensitivity of the driveline to engine excitations.

Finding an optimal compromise between the necessary slip for vibration decoupling and minimizing slip for fuel economy is an area of active research. In this presentation, we describe the implementation of feedback closed-loop control to reduce torque converter slip for improved fuel economy. The use of driveline torsional velocity measurements to quantify driveability under torque converter slip control is also discussed.

Finally, experimental results for a General Motors Sport Utility Vehicle equipped with a 6-speed automatic transmission are presented.