Development and Analysis of Synchronization Process Control Algorithms in a Dual Clutch Transmission
The Dual Clutch Transmission (DCT) is a relatively new kind of transmission
which shows increased e\ufb03ciency and comfort compared to manual transmissions.
Its construction is much like two parallell manual transmissions, where the gear-
shifts are controlled automatically. The gear-shift of a manual transmission in-
volves a synchronization process, which synchronizes and locks the input shaft to
the output shaft via the desired gear ratio. This process, which means transporta-
tion of a synchronizer sleeve, is performed by moving the gear shift lever which is
connected to the sleeve. In a DCT, there is no mechanical connection between the
gear-shift lever and the sleeve. Hence, an actuator system, controlled by a control
system, must be used.
This report includes modelling, control system design and simulation results of
a DCT synchronization process. The thesis work is performed at GM Powertrain
(GMPT) in Trollhättan. At the time of this thesis, there is no DCT produced by
GM, and therefore the results and conclusions rely on simulations. Most of the
used system parameters are reasonable values collected from employees at GMPT
and manual transmission literature.
The focus of the control design is to achieve a smooth, rather than fast, move-
ment of the synchronizer sleeve. Simulations show that a synchronization process
can be performed in less than 400 ms under normal conditions. The biggest prob-
lems controlling the sleeve position occur if there is a large amount of drag torque
a\ufb00ecting the input shaft. Delay problems also worsen the performance a lot. An
attempt to predict the synchronizer sleeve position is made and simulations shows
advantages of that.
Some further work is needed before the developed control software can be used
on a real DCT. Investigations of sensor noise robustness and the impact of dogging
forces are the most important issues to be further investigated. Implementation
of additional functionality for handling special conditions are also needed.
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Last updated: 2021-11-10