Research On Adaptive Start Control Of The Vehicle With Wet Dual Clutch Transmission

Dual clutch transmission(DCT)not only inherits the advantages of mechanical transmission(MT),such as fast shift speed,high transmission efficiency,good fuel characteristics,as well as the advantages of automatic transmission(AT),such as small shifting impact and smooth shifting,but also has the advantages of keeping shifting power continuously.It not only ensures the vehicle power and fuel economy,but also meets people’s requirements for ride smooth and comfort.The friction and wear of the clutch in service lead to the change of clutch performance,which affects the starting and shifting quality of DCT.At present,the research on the starting control strategy of dual clutch automatic transmission mainly focuses on the engine,clutch speed control and oil pressure control.Few literatures consider the change of clutch performance with the increase of service time,which leads to delay,jitter and impact in the vehicle starting process.There are also few literatures on dual clutch automatic transmission The starting adaptive control of the clutch performance changing with the service time.Under the given control strategy,the clutch performance changes with the increase of service time,resulting in the decline of vehicle starting quality.Therefore,it is of great academic significance and application value to study the adaptive control of vehicle starting under the condition of changing clutch performance.In this paper,a seven speed wet dual clutch automatic transmission vehicle is taken as the research object.Aiming at the problem that the starting quality of the vehicle decreases due to the change of clutch performance with the increase of service time,the adaptive control of vehicle starting is carried out in-depth theoretical research and experimental verification.The specific work is as follows:(1)The vehicle dynamic model of wet dual clutch automatic transmission is established.Firstly,the engine steady-state torque model is established by using the engine steady-state torque bench test data,and the engine dynamic torque model is obtained through reasonable correction.Secondly,the structure and power transfer principle of wet dual clutch automatic transmission are analyzed,and the dynamic equations of first gear and second gear single clutch starting of wet dual clutch automatic transmission vehicle are established respectively,and the dynamic equations of stable driving are obtained.Then,the structure and working principle of dual clutch automatic transmission hydraulic system and its actuator are analyzed,and the clutch hydraulic control system model is established,which lays the foundation for the research of vehicle starting adaptive control.(2)In view of the problem that the performance of the vehicle starts down due to the change of the clutch performance with the service time,the starting adaptive control method of the double clutch automatic transmission vehicle is proposed.The starting adaptive control of the dual clutch automatic transmission is divided into two parts: adaptive top control and bottom control.In the top control aspect,based on the established dynamic model of the double clutch automatic variable speed vehicle starting,the fuzzy controller for starting condition identification is designed based on the input of the engine throttle opening and throttle opening change rate,and the output of the target engagement speed and the condition correction factor of the engine.Based on the principle of minimum,the first or second gear starting reference trajectory which can reflect the driver’s driving intention is obtained under the condition of condition correction factor and other constraints.Considering the change of clutch performance leading to the friction coefficient and the engagement oil pressure of clutch plate,an extended state observer is designed.At the same time,the starting dynamics model of double clutch automatic transmission vehicle and the related items of clutch state change are defined as unknown variables.The unknown change term defined in the system is estimated.Combined with sliding mode controller,the stability of the control system can be realized And robustness.In the bottom control,the engine torque tracking control and the clutch hydraulic actuator oil pressure sliding friction adaptive controller are designed,among which the engine torque tracking control adopts PID control,and the clutch hydraulic actuator oil pressure tracking control adopts sliding mode control.On this basis,the simulation and analysis of the first gear 30% throttle slow start and 80%throttle opening emergency start are carried out to verify the effectiveness of the strategy.(3)A starting self-learning control method of dual clutch automatic transmission vehicle based on the prediction of clutch torque transmission characteristics is proposed.Firstly,a general clutch performance model is simplified as a linear function related to the input current of the hydraulic actuator,and the Stribeck friction coefficient function is normalized to obtain the normalized friction coefficient formula related to the speed difference between the master end and the slave end of the clutch.Secondly,the main control parameters reflecting the torque transmission characteristics of the clutch are listed as the parameter vectors,and the non recursive prediction identification method is used to update the parameter vectors to predict the torque transmission characteristics of the clutch in real time.Finally,on the basis of starting adaptive control,the self-learning starting control strategy combined with the prediction of clutch torque transmission characteristics is compared with the strategy without the combination of self-learning starting control.The results show that the starting control strategy with the prediction of clutch torque transmission characteristics has a certain self-learning function,which further reduces the starting vibration and impact of the vehicle and improves the driving performance The starting quality is improved.(4)A wet dual clutch automatic transmission comprehensive performance test bench is designed and built,and the starting adaptive control test of dual clutch automatic transmission vehicle is carried out.Aiming at the change of clutch performance with the increase of service time,the starting test results of new clutch and 40000 km clutch with and without adaptive control strategy are obtained under the conditions of 30% throttle slow start in first gear and 80% throttle fast start in first gear.The experimental results verify the effectiveness of the proposed starting adaptive control method.