Research On Gearshift Control For A Direct-drive Automated Mechanical Transmission

Transmission is the core component of the automotive driveline system, and it affects the dynamic property, fuel economy and riding comfort of the vehicle. Automated mechanical transmission (AMT) is derived from manual transmission (MT) with the integration of servo-actuators into existing system and combines the advantages of automatic transmission (AT) and MT. AMT keeps the high mechanical efficiency, simple constructure, and low manufacture cost of MT, but it must open clutch to change gears. Therefore torque interruption is unavoidable which usually results in power loss and poor shift quality, In order to improve the shift quality and competitive power of the AMT, a kind of direct-drive based AMT which employs a2-DOF electromagnetic actuator is developed and investigated by theoretical analysis, simulation and experiment. The designing of direct-drive based system scheme, building of simulation model and control system are investigated in this thesis to reveal the factors which affect the shift quality, and sectional control, optimal control and robustness control during gearshift process are proposed to improve the shift quality. This thesis lays a foundation for the development of direct-drive based AMT. The main works and fruits of the thesis are as follows:(1) The design requirements of gearshift system and control system for electrically controlled AMT is analyzed, and a kind of novel direct-drive technology based electrically controlled AMT which employs a2-DOF electromagnetic actuator as gearshift actuator is proposed. Since the realization of direct-drive technology results in higher requirements for the control system, the key issues of the control system is investigated and the control scheme is built up. The control platform which includes software and hardware is developed for further research.(2) The gearshift model which comprises engine, clutch, transmission, vehicle and the2-DOF electromagnetic actuator is built for the verification of the control strategy. The combined model of the2-DOF electromagnetic including electric, magnetic circuit and mechanical subsystems are established and the coupling relationship among them is discussed with theoretical analysis method. The parameters are indentified and the influences to the performance of the actuator are analyzed when the static and dynamic characteristics are explored by experiments. Besides, smooth-based Fuzzy-PID control method is proposed to improve the motion control performance, and the method is verified through simulations and experiments. (3) In order to improve the shift quality, sectional control method is proposed according to the different working condition of each phase during the gearshift process. The sectional control method combined with the model of the gearshift system and control system is investigated through simulations and experiments. The closed-loop control of shift off and gear selection process is carried out. Since the actuator can output linear and rotate motion simultaneously and without interference, shift sequence coordinated control is introduced. The simulation and experiment results show that the integrated control method can improve the shift quality distinctly.(4) The indexes of shift quality and the interacting relationship among them are described. In order to achieve the best shift quality, the shock intensity and friction work are adopted as the optimization objective. The objective function is built and the Minimum value principle is used to optimize the function, and the optimal shift force trajectory of the synchronization process is obtained. The relationship between synchronization time and shift force is investigated through simulation, and self-adaption method of shift force during variable working condition is designed. Experiments are carried out to verify the effects of the proposed methods.(5) A kind of compound robustness control method is designed since the direct-drive based gearshift system is nonlinear and easily disturbed by parameter variation and external disturbances. The gearshift process is divided into synchronization process and non-synchronization process. Active disturbance rejection controller (ADRC) is employed to improve the tracking precision and robustness of the optimal shift force trajectory during the synchronization process, and extended state observer (ESO) based inverse system method (ISM) is applied to improve the dynamic characteristics and robustness of the non-synchronization process. Simulation and experiment results shows that the compound robustness control method do enhance the reliability and robustness of the gearshift system. The novel direct-drive based AMT gearshift system has a good application prospect.The results show that the direct-drive AMT can achieve less than170ms of gearshift time when the speed difference is600r/min and the moment of inertia is0.03kg-m2. The shift off time is27.5ms and the shift in time is139.5ms. The maximum shock intensity is188.3rad/s3and the friction work per unit is0.078J/mm2during the gearshift process. The gear selection time is17.8ms. The results verified the superiority of the direct-drive AMT gearshift system and the effectiveness of the proposed control method.