Research On Adaptive Gearshift Control Of The Wet Dual Clutch Transmission

The Dual clutch transmission(DCT)has the advantages of fast gearshift response,uninterrupted gearshift power,good inheritance with manual transmission and high transmission efficiency.Therefore,it has unique advantages compared with continuous variable transmission(CVT)and automatic transmission(AT).Therefore,in recent years,the market share of the dual clutch transmission has gradually increased,and the dual clutch transmission has become the research and development hotspot in the field of automatic transmission.The DCT can achieve fast and smooth gearshift by coordinating the disengagement and engagement of the two clutches,However,with the increase of service time,the change in clutch characteristics will change the torque transmission characteristic of the clutch,resulting in the deterioration of the gearshift performance of the DCT(the gearshift jerk would increase,the gearshift delay would occur,etc.).However,few studies have researched the adaptive gearshift control which adapts to the change in clutch characteristics.Therefore,it is of great academic and engineering value to carry out the research on the adaptive gearshift control which adapts to the change in clutch characteristics.Taking a seven-speed DCT equipped on a certain vehicle as the research object,this study proposes an adaptive gearshift control method which adapts to the change in clutch characteristics.The specific research work includes the following four parts:(1)The dynamic gearshift model of the DCT which can reflect the dynamic characteristics is established;the dynamic model of the clutch hydraulic actuator which can reflect the nonlinear characteristics of the clutch hydraulic actuator is established;the engine steady-state torque model is established by interpolating and fitting the experimental data of engine steady-state torque,and the dynamic torque model of the engine is obtained by modifying the steady-state torque model.(2)The DCT gearshift problem is transformed into a reference trajectory tracking problem,and the gearshift reference trajectories of engine angular velocity and the transmission output shaft angular velocity are obtained by the minimum principle based on the DCT gearshift dynamic model.Then,the terms that vary due to the change in clutch characteristics in the DCT gearshift dynamic model are defined as the uncertain term,and an extended state observer is designed to estimate the uncertain term.On this basis,the gearshift controller is designed using the backstepping method combined with the gearshift reference trajectories.Meanwhile,in order to improve the robustness of the gearshift controller,H∞ robust control is introduced into the gearshift controller designed by the backstepping method,which forms the adaptive gearshift control method based on the extended state observer and the H∞ robust control proposed in this paper.Thereby,the adaptive control laws of the clutch pressure and engine torque are obtained.In order to track the adaptive control law of the engine torque obtained by the adaptive gearshift controller,an engine torque tracking controller is designed based on the dynamic torque model of the engine;in order to track the adaptive control law of the clutch pressure obtained by the adaptive gearshift controller,and considering that the changes in the hydraulic oil density and effective elastic modulus will affect the pressure control performance,an adaptive pressure controller based on T-S fuzzy model and extended state observer is designed on the basis of the dynamic model of the clutch hydraulic actuator.In order to verify the effectiveness of the proposed adaptive gearshift control method based on the backstepping method and the H∞ robust control,and the adaptive pressure control method of the clutch hydraulic actuator,the gearshift and pressure control of the clutch hydraulic actuator of the dual clutch transmission are simulated and analyzed,respectively.(3)Although the gearshift controller designed in(2)can reduce the gearshift jerk and the gearshift delay caused by the change in clutch characteristics by compensating for the engine torque and the clutch pressure,there will be obvious gearshift jerk in the next gearshift.In order to further improve the adaptive effect of the designed adaptive gearshift controller on the change in clutch characteristics,this paper takes the integral of engine angular velocity tracking error and the integral of absolute value of gearshift jerk as performance index,and designs the fuzzy controller based on the adaptive gearshift controller,which forms the adaptive gearshift controller based on fuzzy iteration.The self-learning function of the fuzzy iterative adaptive gearshift controller is used to compensate for the friction coefficient of the clutch friction plate and the pressure of the clutch joint point,so as to eliminate the influence of the change in clutch characteristics on the gearshift performance gradually.Finally,simulation is carried out to verify the effectiveness of the designed fuzzy adaptive gearshift controller.(4)In order to verify the effectiveness of the proposed adaptive gearshift control method of the DCT based on the backstepping method and the H∞ robust control,a gearshift test bench of the dual clutch transmission was built.A new clutch and a clutch serving 40000 km were used to carry out gearshift experiments on the DCT test bench to verify the adaptation effect of the proposed adaptive gearshift control method on the change in clutch characteristics.