International Journal of Automotive Technology , Vol. 18, No. 1, pp. 179 −194 (2017) DOI 10.1007/s12239 −017−0018−4Copyright © 2017 KSAE/ 094− 18 pISSN 1229 −9138/ eISSN 1976 −3832 179ADAPTIVE CONTROL OF THE SHIFTING PROCESS IN AUTOMATIC TRANSMISSIONS G. SHI1, 2), P. DONG1, 2)*, H. Q. SUN1, 2), Y . LIU3), Y . J. CHENG1, 2) and X. Y . XU1, 2) 1)Department of Automotive Engineering, School of Transportation Science and Engineering, Beihang University, Beijing 100191, China 2)Beijing Key Laboratory for High Efficient Transmission and System Control of New Energy Resource Vehicle, Beihang University, Beijing 100191, China 3)Beijing Institute of Space Launch Technology, Beijing 100076, China (Received 29 July 2015; Revised 30 April 2016; Accepted 28 June 2016) ABSTRACT −This paper focuses on the way of keeping shift quality of automatic transmissions consistent in mass production and with mileage accumulation. We investigate the main factors influencing the consistency of shift quality. Test results show that the torque to pressure (T2P) and pressure to current (P2I) characteristics of shifting elements are easily affected. Asimulation model of an 8-speed automatic transmission is established to simulate the dynamic process of clutch-to-clutch shift.Simulation results demonstrate that the change of T2P and P2I characteristics has a significant influence on shift quality. Inorder to compensate for the influences, we develop two adaptive control strategies, i.e., the adaptive control strategies fortorque phase and inertia phase. They make use of the measured speed information and time information to evaluate shift quality. Then the control parameters are tuned to adapt to the change of T2P and P2I characteristics. Vehicle tests verify that the developed adaptive control strategies are effective to keep shift quality consistent in mass production and with mileageaccumulation. KEY WORDS : Automatic transmission, Adaptive control strategy, Shift quality, Torque to pressure characteristic, Pressure to current characteristic 1. INTRODUCTION Thanks to the increasing requirements for CO 2 reduction and fuel economy, automatic transmissions (ATs) tend to have more speeds in recent years, which leads to anincrease in shift operations of daily driving. In order tohave a fast and smooth shift feeling, comprehensive studiesfocus on the control of the shifting process. Integratedcontrol with mutual communication between engine andtransmission is increasingly being applied (Narumi et al., 1990). It enables significant improvements for shift qualityand clutch durability. Examples of such an integratedcontrol method can be found in the work (Lorenz et al., 1990; Cho, 1987; Yang et al., 2001; Sawamura et al., 1998; Goetz et al., 2004; Bai et al., 2013; Guo et al., 2014; Cheng et al., 2015). In the shifting process of ATs, the oil filling of the on- coming clutch is a major source of uncertainty that makesthe pressure overlap in the torque phase a difficult task(Sun and Hebbale, 2005). Song et al. (2011) presented a systematic approach to evaluate the clutch filling dynamicsand to synthesize the optimal pressure. The proposedmethod was validated through experimental investigationand had a good effectiveness for the improvement of shiftquality (Song et al., 2010). Pinte et al. (2010), Depraetere et al. (2011) and Dutta et al. (2014a, 2014b) discussed the application of iterative learning control algorithoms for theengagement of wet clutches, which can maintain a goodclutch filling performance despite the time-varyingdynamics of wet clutches. Meng et al. (2015a) developed an clutch filling control strategy using both feedforwardand feedback control. Simulation results demonstrated thatthe control strategy can effectively decrease the fill timeand the clutch pressure shock. Liu et al. (2016) proposed a clutch filling method for start-stop function, which enablesa precise control of the vehicle launch. In addition to the optimized control of clutch