| Automatic transmission,as the key component of the vehicle,has great effects on the traction ability,ride comfort and fuel cost.The improvement and innovation of the transmission scheme promote the great progress of the automotive technology.In recent years,a novel overlapping shift method between the friction component(such as the friction clutch and brake)and the switch component(such as the one-way clutch,dog clutch,and synchronizor),has been proposed in the filed of automatic transmission.The novel overlapping shift method could achieve seamless shifts.Compared to the firction components,the switch components have great advantages on the cost,reliability and response.Furthermore,the adoption of the switch components in transmission could improve the efficiency,reduce the cost,and reduce the structure.The transmission including the overlapping shift between the friction component and the switch component is called F-S Transmission in this paper.The F-S overlapping shift is selected as the research subject of this paper,and the key technologies,such as the modeling method of the driveline,the gearshift control strategy,and the state estimation of the F-S overlapping shift is studied.The relevant conclusions in this paper are all verified through numerical,simulation and experimental methods.The main research contents of this paper could be summed up as follows.Firstly,the F-S overlapping shift mechanism of the basic 2-speed F-S transmission(FST)has been expressed.The change of the power-flow of the driveline during shifts has been analyized and then the characteristics of the seamless shift have been explained.The dynamic equations in the low gear(including the torque phase and torque resuming phase),the inertia phase and the high gear have been established to analyse the change of the speeds and transmitting torques of the power source,the shift componments,and the output shaft during shifts.The cascading integrated control structure of the 2-speed FST has been introduced,including the planning of shift trajectories,optimal feedward and feedback shift control strategy,the control strategy of the actuators,and the state estimation.Secondly,the simplified dynamic equations of the 2-speed FST have been established for the shift trajectory palnning.The main objective evaluaton indxes of the shift quality are then theoretically analyzed,and two kinds of jerks are distinguished.One kind of jerk is caused by the continuous change of the torque of the power source and the friction component,and the other is caused by the sudden change of the state of the shift conponents at the key monments during shift.Based on the theorectial analyses of the objective function,state equations,path constraints,event constraints in the torque phase,inertia phase,and torque resuming phase,and the joint constraints between the phases,the overall multi-phase shift trajectory global planning problem of the 2-speed FST with variable dynamic structures and complex constraints has been proposed in this paper to achieve the integral optimization of the complex and reciprocal objective evaluation indxes of the shift quality in above phases.Next,the advantages and disadvantages of different solving methods for the optimal control problem have been compared.Legndre pseudo-spectral method(LPM)is chozen for the muti-phase shift trajectory global planning problem of the 2-speed FST.The main solving procedures of the optimal control problem using LPM is expressed in detail.The co-state mapping theorem of LPM has been proved through the comparison of the discrete first-order necessary condition for optimality of the optimal control problem and Karush-Kuhn-Turcker(KKT)condition of the nonlinear programming(NLP)problem to provide an effective approach to test the validity of the obtained optimal solution using LPM.Meanwhile,the solving procedures and co-state mapping theorem of the multi-stage optimal control problem using multi-stage LPM are also expressed.The proposed shift trajectory global planning problem of the 2-speed FST is transferred into a NLP problem and then successfully solved using multi-stage LPM to obtain the optimal shifttrajectories.Then,the dynamic characteristics of the actuator of the friction component and elasticity of the drive shaft have been included in to the dynamic models of the 2-speed FST for the purpose of state estimation.The state variables’ observer has been proposed based on the sliding mode ovserver in order to precisely identify the key moments to engage or disengage the switch component and provide the information of the state variables for the feedback controller in realtime.The selecting method of the feedback gains in the state variables’ observers have been introduced based on the analysis of the dynamic characteristics of estiamating errors of the state variables.Finally,the deiveline system of an electric vehicle(EV)with 2-speed inverse automated transmission(I-AMT)is selected as the actual research object in this paper.The vehicle driveline dynamic system simulation model including dynamic models of the power system,driveline system and vehicle has been established on the platform of AMESim,and the simulation models of the shift controller and the state variables’ observer have been built up on Matlab/Simulink software.Furthermore,the shift test-bench of F-S overlapping shift has been constructed based on the developed prototype of the 2-speed I-AMT.The corresponding upper test and control system of the test-bench has been built using the Matlab/ RTW tool.Several shift simulations and experiments under different conditions have been carried out,and the simulation and experimental results show that: the proposed state variables’ observer could estimate the state variables precisely,decide the moments to engage and disengage the switch commpont well,and provide the estimated state variables for the feedback controller in realtime;the propose optimal harmoniously shift control strategy could reduce the fluctuate of the output shaft torque and the jerk,prelong the life-span of the shift components,and improve the shift quality.The reseach work of this paper provides theoretical foundation and technical guidance for the developments and furture applications of not only F-S overlapping shift method,but also the overlapping shift between friction components in the seamless transmissions,such as dualclucth transmission(DCT)and automatic transmission(AT). |
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