Research On AMT Drivability Improvement During Shift Process And Control System Development

Automated Manual Transmission(AMT)has the advantages of high transmission efficiency,low manufacturing cost,small size and low weight,which generally adopts the traditional mechanical gearbox structure,and the automatic shift control system composed of automatic dry clutch and automatic shifting actuator.However,compared with other types of automatic transmissions,AMT has no flexible transmission device while the dry clutch without oil film buffer plays a decisive role in the gear switching process.In addition,there are many uncertain factors in the shift process(clutch friction,External time-varying environmental parameters,etc.),so the driving experience in AMT during the shifting process is poor and the drivability is difficult to control.However,the drivability is one of the most important indicators to evaluate the performance of vehicle,which can reflect the dynamic performance of the transmission route.In order to solve the industry problem that it is difficult for AMT vehicles to ensure the consistency of driving quality control effects,how to improve the shifting quality while ensuring the dynamics,economy and meeting emission conditions is an important topic worthy of in-depth study.One of the most important ways to improve the AMT drivability during shifting is to apply an electronic control system with electromechanical coordination and optimize its control effect.However,the continuous advancement of the process of electrification,intelligence,and networking has put forward a higher level of current automotive electronic control systems.AMT control systems traditionally adopts the rule-based feedforward map+feedback PID control methods,which are simple and easy to implement,but increasing the calibration workload of actual vehicle tests.That phenomenon maks the software code volume in product-level automatic transmission control system has surpassed the limitation of engineers currently.In addition,the vehicle has the characteristics of complex environmental conditions,multiple control inputs,strong coupling,etc.It also has a variety of objectives(fuel economy,emissions,power and comfort,etc)and operating conditions(vehicle launch,gear shift,extreme conditions,etc).For the rule-based control methods mentioned above,the calibrated control parameters under specific operating conditions cannot achieve the optimal shift quality under all operating conditions,especially transient conditions.In response to this problem,the model-based vehicle control system design method,adding the link of designing the controller through specific dynamics is a better solution.It can not only guarantee the control performance during transient working conditions,but also avoid the complicated control parameter calibration work under different working conditions.In response to the above problems,this article relies on the National Science Fund for Excellent Young Scholars Project(Project Number: 61522307),Jilin Province Science and Technology Department,young and middle-aged leaders in science and technology innovation and team projects(Project Number: 20200301011RQ)and Jilin University,undergraduate education reform project(Project Number: 2019XYB161),carried out research on AMT in the optimization of drivability during shifting process and the development of its control system.Aiming at the key problem of clutch slip,the optimal control law with disturbance rejection of "system disturbance estimation + disturbance system optimal control" and a shift parallel control strategy of clutch slip and driving torque recovery phase are designed.A development process including explicit anti-disturbance control law design,virtual calibration tool development,rapid prototype road test verification,etc.is proposed.The comprehensive performance of slipping work/jerk under any shifting conditions and the calibration work at the engineering application level are optimized.And the engineering application of advanced control theory in the development of automotive control system is realized.The main research contents of this paper are as follows:(1)Control system development process based on explicit control law designThrough the analyses of the clutch engagement law(rule-based "fast-slow-fast" engagement law),control method(based on feedforward map+feedback PI controller)and traditional development processes traditionally used by OEMs,the common defects are refined while the forward development process of the AMT control system which follows the model-based concept is proposed.By adding an explicit control law that can optimize the shift quality in the controller design link,the development process is compared with the traditional development process.And the result shows that,the development process is superior to the traditional development process in terms of design ideas,verification links,control effects and technical maintenance.(2)Anti-disturbance optimal explicit control law and design of parallel control strategy for shifting processOn the one hand,through the analysis of performance evaluation indicators and control objectives during the AMT shifting process,a plant model of the control-oriented transmission is simplified into a "two-mass" model and organized into the form of state space equations.Based on the objective function and the principle of maximum value,a new form of Lagrangian multiplier function is introduced,which helps the derivation of optimal explicit control law for disturbance rejection.Also,the disturbance observer that can use the pole configuration for convergence adjustment is designed.On the other hand,by analyzing the dynamic phase of the AMT upshift and downshift process,a parallel control shift strategy of "clutch slip phase" and "drive torque recovery phase" is proposed,which can take into account the driving quality and shift time of upshift or downshift.(3)Development of virtual calibration tools for engineering applicationsTaking into account the huge cost of time,workload and material resources involved in the traditional calibration process,based on the idea of "tooling" the control algorithm,a visual virtual calibration tool is designed using software-in-the-loop technology.The initial interface distribution of the MATLAB/GUI modules,the tools used in software and the function realization process of the tools are introduced in detail.It can realize the transfer of the calibration work of the vehicle/test platform to the virtual end in the computer,which greatly reduces the calibration workload at the vehicle level and makes up for the gap between researchers and developers.(4)Co-simulation and real-vehicle test verification and analysisFor the anti-disturbance control law and shift control strategy proposed above,this paper adopts multi-directional verification methods: software-in-the-loop co-simulation based on MATLAB/Simulink+AMESim,rapid controller prototype testing based on d SPACE Micro Auto Box,and road test of system integration based on the vehicle-level control unit Rapid ECU-U2 M.In order to highlight the anti-disturbance performance of the proposed method,nominal conditions,disturbance conditions and road driving conditions are selected for co-simulations and experiments.The experiment results show that,the proposed development method has advantages in many aspects,such as real-time test,control effect,and calibration cost.