Adaptive fuzzy iterative control strategy for the wet-clutch filling of automatic transmission

In the gear shifting processes of an automatic transmission (AT), fast and smooth transitions between different gears without drivetrain jerking are always expected, which leads to a desire for high-quality clutch-to-clutch shifts. The accurate and effective filling control of clutches is the base for achieving desirable clutch-to-clutch shifts. This study focuses on developing an adaptive fuzzy iterative control strategy for the filling process of wet clutches in ATs. Firstly, a specific structure and dynamic characteristics of the wet clutch actuating system is analyzed to assist in the designing of control strategies. Afterwards, three types of deviations that usually occur in the filling process, named as speed drop, clutch tie-up and engine flare respectively, are defined and analyzed according to their different characteristics. The adaptive control strategy is then developed to realize the reduction of the deviations. The concrete adjustment performed by the control strategy is based on the features of the previous deviations during the adaptive iteration. Moreover, a double-input-and-double-output fuzzy logic controller (DIDO-FLC) is designed and introduced in the control strategy, which can adjust the fast filling time and the maximum fast filling pressure of the clutch simultaneously. In order to validate the proposed strategy, the results of vehicle test are presented, which demonstrate that the deviations are effectively diminished and the shifting quality is obviously improved. (C) 2019 Elsevier Ltd. All rights reserved.