Torque Sensor based Powertrain Control
The transmission is probably the drivetrain component with the greatest impact on driveability of an automatic transmission equipped vehicle. Since the driver only has an indirect influence on the gear shift timing, except for situations like kick-down accelerations, it is desirable to improve shift quality as perceived by the driver. However, improving shift quality is a problem normally diametrically opposed to minimizing transmission clutch energy dissipation. The latter has a great impact on transmission lifetime, and has to be defined and taken into consideration along with the notion of shift quality. The main focus of this thesis is the modeling of a drivetrain of an automatic transmission vehicle, and the implementation in MatLab/Simulink, including the first to second gear upshift. The resulting plant based on the derived equations is validated using data from a test vehicle equipped with a torque sensor located at the transmission output shaft. The shaft torque is more or less proportional to the driveline jerk, and hence of great interest for control purposes. Control strategies are discussed and a PID controller structure is developed to control the first to second gear upshift, as opposed to the traditional open-loop upshift control. Furthermore, the proposed controller structure uses the transmission output torque and the differential speed of the engaging clutch as inputs, to control the clutch pressure and the engine output torque, respectively. The structure is unsophisticated and transparent compared to other approaches, but shows great theoretical results in terms of improved shift quality and decreased clutch wear.
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