Research On Gearshift Control For Dual Clutch Transmission Based On Objective Evaluation

In recent years, the dual clutch transmission (DCT) with advantages of high efficiency,excellent shift quality as well as good production inheritance has attracted the attention ofmany domestic and foreign vehicle and parts manufacturers. The shift control technology ofDCT is the core technology of electronic control system development, whose main researchcontents are gear shift decision and shift process control. In this dissertation, research ofDCT shift control technology based on shift quality objective evaluation was conductedsystematically to improve the shift quality and system robustness, shorten the developmentcycle of control system and save costs combined with "863" high-tech program fundedproject―Development of Technology of Dual Clutch Transmission Industry-Development ofShift Quality Objective Evaluation and Digital Calibration (2012AA111712)" and Ph.D.Programs Foundation of Ministry of Education of China―Research on Key Technology ofDigital calibration of automatic transmission(20120061110027)‖. On the whole, this paperfocus on the research of shift quality objective evaluation based on ideal shift process, gearposition decision based on power reserve, shift process integrated control strategy andoptimization of shift quality. The main contents are as follows:1) Modeling and simulation of the vehicle system. The DCT vehicle dynamicssimulation platform was built including engine model, the clutch and operating mechanismmodel, transmission model, vehicle load model and driver model. Mean value modelcontaining intake manifold, the fuel vapor and oil film and power output sub model wasadopted to simulate steady state and dynamic response of the engine. Clutch actual torquewas simulated with static friction+coulomb+hyperbolic tangent friction model. Relationcurve between friction coefficient with temperature and the slip speed was measured byexperiment. The working mechanism of clutch hydraulic control system was analyzed andthen a simplified model of operating mechanism including PWM solenoid valve and clutchhydraulic cylinder module was set up. Launch and shift process mathematical model werestudied based on this DCT vehicle dynamics simulation platform under considering DCT different working conditions. The effectiveness and reasonability of this simulation platformwas varied by simulate shift process under typical working conditions.2) Research on shift control objective evaluation method based on ideal shift process.The concept of ideal shift process is proposed based on model simulation. The objectiveevaluation index system of DCT shift process are analyzed and built from the perspectives ofdifferent signal source. Data acquisition scheme for extracting indexes is designed, andCanoe-Matlab Co-simulation technology is adopted to realize on-line extraction of objectiveevaluation indexes. Clustering analysis was applied to classifying the proposed objectiveevaluation indexes and the principal component analysis (PCA) were conducted to optimizethe index system based on the classification results. The shift quality objective evaluationmodel based on ideal shift process was developed to realize on-line and off-line shift qualityobjective evaluation.3) Research on gear position decision method based on power reserve. The concept ofpower demand was proposed and translated into limited value of reserve power throughtheoretical analysis. Considering the computation requirement of limited value of reservepower at constant velocity, the estimation algorithm of vehicle load and road slope based onEKF was developed and then the method was verified by simulation using road test data.This paper applies the dynamic programming (DP) to the development of DCT static shiftschedule to decouple the vehicle power performance and fuel economy. Finally, gearposition decision method based on power reserve was realized based on the shift schedule.4) Research on DCT shift integrated control strategy and optimization of control quality.Gearshift principle under typical working conditions was analyzed and the coordinationcontrol of two clutch pressure in torque phase was emphatically analyzed using simplifiedmodel of shift process. The integrated control strategy for power-on upshift and downshiftwas proposed. Slip speed controller of off-going clutch was designed during torque phasebased on the quadratic optimal control theory which can meet the requirements of accuracycontrol of slip speed and response speed. Sliding mode variable structure control method wasproposed to achieve fast and high precision control of clutch pressure in allusion to the nonlinear and time-varying characteristics of the actuator. The particle swarm optimization(PSO) algorithm was adopted to search the optimal solution of control parameters for theproposed integrated control strategy and the evaluation model based on ideal shift processwas taken as the fitness function of PSO to accelerate convergence, which was verified bysimulation.5) The vehicle test validation. Test program is designed to collect data samples of shiftprocess by carrying out multiple DCT types vehicle tests and then database was built. Thedatabase can provide effective calibration data and benchmark for the development ofcontrol system. DCT gearshift control system software was developed based on reliable TCUhardware platform. Finally, the effectiveness and reasonability of gear position decisionmethod based on power reserve, shift process integrated control strategy and optimization ofshift quality were verified by vehicle test.