| With the increasing depletion of global oil resources and the growing pollution of the environment,the emission regulations of all countries in the world continue to improve,so that the new energy vehicles have been developed rapidly.However,due to the problems of short driving range,long charging time and technical obstacles in electric vehicles,and the cost of fuel cell vehicle is high,so that their developments have been limited.Therefore,hybrid electric vehicle has become the most promising new energy vehicle.In the driving process,the hybrid power system will change the working mode according to the driving intention and the component status,in order to improve the power or energy consumption of the whole vehicle.However,during the mode switch of hybrid power system,it is necessary to coordinate the relevant components,if the control is not proper,the hybrid drivetrain will produce a large torque ripple,which will affect the rid comfort of vehicle.Therefore,it is necessary to develop a reasonable dynamic coordinated control strategy for the mode switch of hybrid system.Aiming at the ride comfort of driving mode switch of CVT plug-in hybrid system,the main work research results are as follows:(1)The structural characteristics of the CVT plug-in hybrid system are analyzed,and the parameters of whole vehicle and main components are determined.Meanwhile,the torque characteristics of the main components are analyzed,and the simulation model of the related components is established,which lays a foundation for simulation analysis of the dynamic coordinated control process.(2)The working conditions of main components are analyzed under different drive modes,and the dynamic equations of system are established,which lays a foundation for the analysis of mode switch process.The causes of torque ripple of hybrid drivetrain are analyzed in the mode switch process,and the mode switch process is defined as two phases to control.The evaluation index of impact is given,and the two phase impact of mode switch is analyzed respectively.The dynamic analysis of the CVT fast response to target speed ratio during mode switch is carried out,and it is concluded that the additional torque caused by change of CVT speed ratio is the main cause of torque ripple.The dynamic analysis of power source and clutch working status change during mode switch is carried out,and it is concluded that the change of torque between power source and clutch is the main cause of torque ripple.(3)The torque management strategy is studied briefly in the driving mode,which lays the foundation for the analysis of mode switch.Aiming at the problem of torque ripple of hybrid drivetrain caused by CVT fast response to target speed ratio during mode switch,a dynamic coordination control strategy of ‘motor torque compensation control and CVT speed ratio change rate control' with impact degree as control target is put forward.Aiming at the problem of torque ripple of hybrid drivetrain caused by change of power source and clutch working status,a dynamic coordination control strategy of ‘motor torque compensation control and engine throttle change rate control' with impact degree as control degree is put forward.On this basis,the implementation of dynamic coordination control of mode switch process is analyzed.(4)A forward simulation model of CVT plug-in hybrid vehicle and a simulation model of vehicle control strategy are established on MATLAB/Simulink/Stateflow and Simscape platform.The comparison analysis of CVT fast response to target speed ratio mutation phase is carried out through the simulation,and the comparison analysis of power source and clutch working status change of second and third types mode switch is carried out through the simulation.The simulation results show that the mode switch with dynamic coordination control strategy can effectively reduce the torque ripple of drivetrain and improve the ride comfort of vehicle. |
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