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Driveline Modeling and Control

Past project

Driveline Modeling and Control

The vehicular driveline is a fundamental part of a vehicle. It consists of engine, clutch, transmission, shafts, and wheels. Since these parts are elastic, mechanical resonances may occur. These resonances affect performance and driveability of the vehicle, and the handling of such resonances is thus important when developing new driveline management systems. Two systems where driveline oscillations limit performance is speed control and automatic gear shifting.

Speed Control

Speed control is the way the driver's accelerator position is transfered to speed. The fuel amount to the engine is controlled such that a certain speed on the driving wheels is obtained. With the RQV control scheme, traditionally used in diesel trucks, the elasticity of the driveline will result in oscillating wheel speed, known as vehicle shuffle. These oscillations can be reduced by using the wheel speed sensor, but then an increased controller gain will result in an unstable system which limits the bandwidth. To avoid these problems with vehicle shuffle, a new idea is formulated which utilizes model based control that achieves the desired wheel speed with actively damped oscillations.

Gear-Shift Control

In todays traffic it is desired to have an automatic gear shifting system on trucks, and one new way of achieving this is to use engine controlled gear shifting. With this approach a gear shift can be performed with a manual transmission, but without using the clutch. A critical step in this scheme is to control the torque transferred in the transmission to zero, whereafter neutral gear can be engaged. It is clear that driveline oscillations is an important performance limiting factor if they are not damped out. This is because the system has to wait until satisfactory gear shift conditions are reached, and thus increasing the total time needed for a gear shift. This work is a novel extension of an existing system with active damping of driveline resonances. The strategy offers a possibility to optimize the time needed for a gear shift, which is important especially when driving uphill with heavy loads. Furthermore, neutral gear can successfully be engaged also when facing critical load disturbances and initial driveline oscillations.

More information about these research topics can be found in "Automotive Control Systems" by U. Kiencke and L. Nielsen.

Informationsansvarig: Lars Nielsen
Senast uppdaterad: 2010-11-29