Research On Power Shift Control Strategy Of Combined Transmission Of High-power Tractor

The research object of this subject is the combined transmission of high-power tractor.The automatic transmission process of the tractor can be divided into two parts: the power-on shift process in which the two clutches simultaneously participated in and the four clutches simultaneously participated in.This paper establishes reasonable shifting control strategies for the power-on shifting sequence of double clutch and four clutch respectively to control the power-on shifting and to ensure that the power of tractor is not interrupted during operation.The details are as follows:(1)In view of the power shift process in which two clutches are involved,control only one clutch has sliding state in the shift process.Considering avoiding the power cycle of the shift,a power shift control strategy based on the torque and speed transfer stages is proposed,which can effectively avoid the power flow cycle,realize the tractor power-on shift without interruption and adapt to the change of resistance.Considering the shift characteristics in different stages,the simulation model of power-on shift with dual clutch is established.(2)Considering the power-on shift process in which two clutches are involved,based on the optimal control theory of minimum principle,the optimal control of shift quality in the process of power-on shift with double clutches participated in is carried out.The optimal terminal oil pressure of the clutch is determined by solving the Rebecca differential matrix equation,which can effectively reduce the output torque fluctuation in the process of power-on shift,reduce the sliding work and improve the shift jerk.(3)Considering the power-on shift process in which four clutches are involved,different shift action schemes are analyzed by taking the power shift process from middle gear to high gear as an example.The ‘up-down' shifting scheme and the ‘down-up' shifting scheme are determined by analysis.The power-on shift models of the ‘up-down' shifting scheme and the ‘down-up' shifting scheme are established respectively.By comparing the simulation results and considering the influence two different shifting schemes made in the shift performance,the ‘down-up' power-on shift control strategy is determined,which can realize the uninterrupted power shift process with four clutches participated in.