An automatic gear-shifting strategy for manual transmissions

OILPAN

An automatic gear-shifting strategy for manual transmissions

B Mashadi*, A Kazemkhani, and R Baghaei Lakeh
Department of Automotive Engineering, Iran University of Science and Technology, Tehran, Iran
The manuscript was received on 25 February 2006 and was accepted after revision for publication on 3 April 2007.
DOI: 10.1243/09596518JSCE253

Abstract: Based on two different criteria, namely the engine working conditions and the
driver’s intention, the governing parameters in decision making for gear shifting of an automated
manual transmission are discussed. The gear-shifting strategy was designed by taking into
consideration the effects of these parameters, with the application of a fuzzy control method.
The controller structure is formed in two layers. In the first layer, two fuzzy inference modules
are used to determine the necessary outputs. In the second layer a fuzzy inference module
makes the decision of shifting by upshift, downshift, or maintain commands. The behaviour
of the fuzzy controller is examined by making use of ADVISOR software. It is shown that at
different driving conditions the controllers make correct decisions for gear shifting accounting
for the dynamic requirements of the vehicle. It is also shown that the controller based on both
the engine state and the driver’s intention eliminates unnecessary shiftings that are present
when the intention is overlooked. A microtrip is designed in which a required speed in the
form of a step function is demanded for the vehicle on level or sloping roads. Both strategies
for the vehicle to reach the maximum speed starting from rest allow the gear shift to be
made consecutively. Considerable differences are observed between the two strategies in the
deceleration phase. The engine-state strategy is less sensitive to downshift, taking even
unnecessary upshift decisions. The state intention strategy, however, interprets the driver’s
intention correctly for decreasing speed and utilizes engine brake torque to reduce the vehicle
speed in a shorter time.
Keywords: automated manual transmission, gear shifting, driver’s intention, engine state,
fuzzy logic

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