Optimization And Control Of The AMT Without Torque Interruption For Electric Vehicle

The multi-speed transmission can help improve the power and economy of electric vehicles,which is an important research content of electric vehicle drive system.Due to factors of cost and efficiency,most of the multi-speed transmissions for electric vehicles are based on the Automatic Mechanical Transmission(AMT).The AMT can realize multi-speed drive,and also has high efficiency,simple structure,low manufacturing costs.However,the AMT uses synchronizers to switch the power route,so there is an unavoidable problem of torque interruption during the shifting process.In addition,because the motor has good speed regulation characteristics,the main clutch in the AMT is generally canceled.This simplifies the structure of the transmission system,reduces costs,and the number of actuators needed to control.However,it further increases the difficulty of controlling.The torque interruption leads to the deterioration of driving quality.Relying solely on the active speed regulation of the motor,the problem of tooth hitting of the synchronizer(or tooth sleeve)will be more frequent,which will easily cause gear shift failure.These problems limit the large-scale application of AMT for electric vehicles.Solving the problem of torque interruption during the gear shifting process of AMT mainly includes two types of technical routes,namely,the Multi-Power technical route and the Multi-Route technical route.Taking the Multi-Power technology route as an example,dual motor can be used.During the shifting process,two motors are switched to replace gears to ensure continuous output of driving torque.Taking the Multi-Route technology route as an example,during the shifting process,the frictional elements in the additional power route can be used to help drive the vehicle.In the above two solutions,in order to avoid motion interference and reduce impact during the shifting process,the control accuracy of the motor and synchronizer(tooth sleeve)is extremely high.At present,the control process of AMT mostly adopts a rule-based feedforward and feedback control method.In order to make the shift quality in each working condition meet the requirements,a large amount of calibration work is required.Model-based shifting process control has been the main research direction in recent years.Because the model contains the kinematic relationship between the transmission and the vehicle,it can respond to the system state in real time,which can reduce the calibration of redundant control parameters.But the model-based control method has high requirements on model accuracy.In addition,during the actual driving of the vehicle,its own parameters and environmental factors change in real time.These disturbances will have a great impact on the control effect.This paper relies on the National Natural Science Foundation Excellent Youth Science Fund(61522307 automotive transmission system control),and the National Natural Science Foundation of China(61374046 mechanical automatic transmission rolling optimization control)to solve the problem of torque interruption during the shift process of the electric vehicle AMT.The research work starts from the theoretical analysis of gear shifting,structural topology optimization design,proposal and demonstration of key components for gear shifting,optimal control of shifting process,and experimental verification.The research is made from three aspects: the optimization of the AMT structure,the optimization of the key components,and the establishment of the control strategy for the shift process.The main research work of this paper is as follows:First of all,the new energy vehicle transmission system is introduced,and the analysis of the demand for multi-speed transmission of electric vehicles and the improvement of vehicle performance are carried out.Aiming at the problem of torque interruption in the AMT gear shifting process,an Inverse Automatic Mechanical Transmission(I-AMT)scheme using rear clutch is optimized.The one-way clutch is used instead of the traditional synchronizer,which can effectively avoid the motion interference and simplify the gear shifting process.For the reverse gear process of the I-AMT,a Friction Selectable One-Way Clutch(FSOWC)is designed.The FSOWC system does not require a separate actuator.During the shifting process,the I-AMT only needs to control the separation and combination of the rear clutch to achieve continuous torque output.Then,the wedging characteristics of FSOWC system are studied.For the I-AMT used in light electric vehicles,the FSOWC system has been parameterized.The dynamic state model has been used to verify the relationship of various parts during the shifting process.The thermal load analysis of the friction process verified the reliability of the system during continuous reverse gear.Aiming at the wedging process,the influence of the instantaneous wedging on the self-load and the torque fluctuation of the transmission system under different angular accelerations of the master and slave of the selectable one-way clutch was analyzed.Control requirements for the shifting process of I-AMT are put forward.After that,the shifting process of the I-AMT is optimized.Based on the modeling of the I-AMT shift process,taking the friction loss of the rear clutch and the vehicle shock as the optimization goals,a time-varying disturbance rejection controller based on linear quadratic regulator for the shift process of electric vehicles is proposed.Aiming at the parameter uncertainties and external environmental disturbances,a high-order observer is designed to estimate the disturbances and disturbance derivatives.The time-varying disturbances and the derivatives of the disturbances are used as part of the final control law.Compared with the Linear Quadratic Regulation(LQR)controller,the designed controller can ensure stable shift effect when the parameters of the rear clutch of the I-AMT,the vehicle load and the road slope resistance are changed.Finally,bench tests and real vehicle tests verify the shift characteristics of the I-AMT equipped with FSOWC system.The effectiveness of the proposed shift process control strategy is also verified.The results show that under different disturbances,the I-AMT can achieve good and stable shift effect.