Research On Synchronization Control Strategy On Wet DCT Shift Process

This topic is based on the school-enterprise cooperation project: Research and Development of CVT&DCT Control Function.Taking a 7-speed wet dual clutch automatic transmission as the research objectives,the research on synchronization control strategy is carried out to solve the problems of synchronized shock and shift failure during the shift process for lack of control accuracy and response delay.In terms of the mechanical structure and hydraulic system of 7WDCT,this paper introduces the power transmission routes of different gears and working principle of the hydraulic system for synchronizer operation.Then based on dynamic analysis of the synchronization process,the special position points during the synchronizer moving process are defined,including the neutral position point,synchronization point,steady-state in-gear position point,etc.After that,the vehicle model is developed with AMEsim,including engine model,clutch model,synchronizer model and vehicle dynamic model,to simulate the synchronization process.A DCT synchronizer segmentation control strategy is developed based on theoretical analysis and simulation verification.The whole synchronizer pre-shift process is divided into several phases: pre-charged,free stroke,synchronization process,dial ring process to full engagement,after which,the switching conditions and control algorithms in each phase are formulated to achieve a quick impact-free pre-shift process.What's more,the ASCET software is used to build the corresponding control model and automatically generate the C code,then completing software integration,presetting control parameters,and refreshing the software of TCU.After that,the vehicle road test is carried out to verify the developed control strategy,observing the control variables with INCA and analyzing the test data with MDA.In response to the problems encountered during the vehicle test,such as synchronized shock and engagement failure,the control strategies and control parameters are optimized in real time.The synchronization segmentation control strategy proposed in this paper can formulate the appropriate control algorithm for different synchronizer motion stages.The vehicle test results show that the strategy can achieve precise control of the synchronizer on wet DCT pre-shift process,the synchronization time is within the desired time,and it can solve the problems of synchronized shock and engagement failure as well.Furthermore,the control strategy has been successfully applied to the vehicle transmission control,to realize the synchronizer pre-shift process.