Research On Key Technologies Of Time Overlap Gear-shifting For AMTs

Automatic transmissions adopt the actuators to realize automatic switch of gears.It eliminates frequent manual operations in the manual transmissions(MTs),reduces the labor intensity of drivers,and improves the dynamic,economic,comfort and safety performance of vehicles.Therefore,it has been widely used and developed in the automotive field.Automated mechanical transmissions(AMTs)are derived from MTs with robotic devices for transmission,clutch and engine,so lots of operations from the driver are canceled.Compared with other types of automatic transmissions,AMTs have the advantages of high efficiency,compact structure,low cost and good inheritance.However,AMTs have torque interruption during the gear-shift process,which limits their extensive application and development.In order to overcome this problem,a time overlap gear-shift system based on direct-drive was developed by theoretical analysis,simulation and experiment.The modeling of gear-shift process,time overlap gear-shift control,motion control and sensorless control of the actuators were investigated in this thesis.The main works and fruits of the thesis are as follows:(1)The requirements of shift quality and actuator design were proposed for AMT gear-shift system.The differences in structure and working process between the sequential gear-shift and the time overlap gear-shift were compared,which revealed that the time overlap gear-shift can effectively reduce the shift time.Through the comprehensive comparison of different types of shift actuators,the time overlap gear-shift system which applied the moving coil linear DC motor as the direct-drive actuator was developed.The actuator prototype and the functional test bench were designed.The electromagnetic linear actuator(EMLA)was modelled by theoretical analysis,and the coupling relationship between electric circuit,magnetic circuit and mechanical subsystem was discussed.The static and dynamic performances of the EMLA were researched by simulation and bench testing.(2)According to the combination state of the gears,the relative position of shift elements and the distribution characteristics of gear-shift resistance,the kinematics modeling of the gear-shift process were carried out in stages.The working principle of lock-ring inertial synchronizer was described,the reason of unsynchronous gear-shift impact was analyzed theoretically,and the shifting force condition to avoid this phenomenon was deduced.(3)The control targets of different stages in gear disengagement process and gear engagement process were proposed on the basis of kinematics analysis of the gear-shift process.According to the requirement of time coordination in the gear-shift process,the time overlap control strategy was introduced.The constraint condition of the shift force in synchronizing phase was analyzed,and the feedback control strategy was designed.The gear-shift process based on PID control was simulated and tesed.Then,the problems faced by PID control in time overlap gear-shift system were explained.This chapter lays a foundation for further study on the motion controller of EMLA.(4)The reasons for the contradiction between set-point tracking and disturbance rejection in the traditional feedback control system were discussed.The independent design principle of the two-degree-of-freedom(2DOF)control system for these two performances was explained.Since the existing 2DOF control methods were partial coupling between these two performances,the controller design and parameter adjustment processes were inconvenient.To resolve this problem,designing a complete decoupling control system was the key.The improved controller was designed based on linear active disturbance rejection control method.The unit inverse system was introduced as the input feedforward controller.And the reference model was designed to arrange the transition process and to provide input signal for the feedforward controller.The controller design process applied the bandwidth method,so the reference model design and the control parameter adjustment were simplified.Finally,the proposed 2DOF cascade position control method was validated by simulation and experiment.(5)In order to solve the problem of decreased reliability of systems,which caused by over-reliance on the position sensor,a sensorless control method based on self-sensing capability of EMLA was designed for the time overlap gear-shift system.Using Lyapunov stability theory,an improved speed estimation algorithm based on the back electromotive force was proposed.In order to improve the estimation precision,the current differentiation was eliminated via designing an auxiliary,the actuator coefficient was identified and corrected,and the phase advance algorithm of the current signal was employed.Combining the characteristics of velocity and position estimator,the piecewise control method was proposed for the position control system,and the model assisted reduced order extended state observer was used to observe the disturbances in the mechanical subsystem.Finally,experimental results showed that the sensorless control system could satisfy the requirements of the gear-shift system.The control performance of the system in the case of position sensor failure was improved,and the reliability of the system was enhanced.