Research On Automatic Shift Control Strategy For Digital Hydraulic Driving System Of Engineering Vehicles

As a kind of self-propelled power machinery,engineering vehicles are widely used in various fields.However,the working efficiency of the hydromechanical transmission system used in the current construction vehicles is low,resulting in poor economic performance of the vehicle.The high cost of hydrostatic transmission system and the high requirements of key parts for oil cleanliness limit its application.Therefore,this paper gives a new solution combined with digital hydraulic technology,and studies the configuration of engineering vehicle drive system and automatic shift control strategy,which is of great significance to improve fuel economy and realize automatic control.Firstly,on the basis of comparing and discussing the characteristics of different schemes of hydrostatic transmission system,combined with the unique advantages of digital hydraulic technology,the configuration of digital hydraulic transmission system is determined as a high-speed configuration scheme of split open digital hydraulic transmission system.Explain how digital pumps,motors,and digital hydraulics work.On the basis of fully discussing the engine performance,according to the flow continuity equation and the energy conservation equation,the dynamic matching of the transmission system is completed with the minimum fuel consumption of the engine as the goal.According to the calculation results of vehicle dynamics parameters,the models and parameters of key components in the walking system are determined.Secondly,the shifting mechanism of the digital hydraulic travel drive system is discussed and analyzed,and the control variables of the hydraulic system are determined.Different working modes are divided according to the number of gears and the range of transmission ratios.The selection of specific shift parameters suitable for the digital hydraulic system is discussed,and the automatic shift control law is drawn up accordingly.Taking the current gear,motor speed and motor torque as the input parameters of the network,and the output as the execution action,namely upshifting,downshifting and maintaining the current gear,a BP neural network prediction model is constructed.By calculating the average deviation between the network output results and the actual results,the shifting effect obtained is ideal.Then,according to the matching parameters and calculation results,based on the AMESim-Simulink co-simulation platform,the numerical simulation method is used to analyze and evaluate the shifting process of the digital hydraulic traveling system,and the physical model and control model of the system are constructed.Qualitative and quantitative simulation analysis and discussion of the constructed model.The simulation analyzes the shift results of the control system according to the motor torque and motor speed under three different modes of heavy load,light load and transportation.And discuss the effect of gear changes on the transmission system in different modes.The results show that the physical configuration proposed in this paper can be applied to the field of engineering vehicles.The formulated control strategy can realize automatic gear shifting according to parameter changes.Finally,this paper designs the overall structure and experimental ideas based on the existing conditions of the experimental bench.Completed the variable pump displacement control experiment,the hydraulic system gear and motor speed calibration experiment,and the constant torque variable speed automatic shifting verification experiment.The experimental results show that the control system can automatically shift gears according to the change of the target speed of the motor,and the obtained error is within an acceptable range,and the theoretical and simulation analysis process has been verified.At the physical level,the rationality of the walking system structure and the correctness of the control strategy are proved.For the research of the hydraulic walking system,this paper adopts the method of formula derivation and numerical simulation to carry out theoretical analysis,and then combines the bench experiment to verify from the physical level,and the results meet the expectations.An effective method is provided for the research on the configuration of the running system of the engineering vehicle and the control law of automatic shifting.