Research On Electro-hydraulic Servo Loading System For Steering Testing Of Heavy Vehicle

Heavy wheeled vehicle is widely used in the fields of transportation,agriculture,mining and military equipment because of its heavy load and high transportation benefit.Because of its large number of axle,long body and large tonnage,the low speed driving flexibility and high speed running stability are poor.Therefore,the performance of the steering system determines the driving characteristics of heavy wheeled vehicle.The key to the development of high performance steering system is to understand the different driving conditions of the vehicle.The steering test bench for heavy vehicle is required to realize a variety of working conditions for steering.The electro-hydraulic servo loading system is an important part of the test bench.Aiming at various steering conditions of heavy vehicle,this paper designs an electro-hydraulic servo loading system for heavy vehicle steering test platform,and carries out accurate control research on the loading system.First,based on the actual steering conditions,the design requirements of the loading system are put forward,and the hydraulic system and the mechanical structure part are designed accordingly.According to the actual driving condition of the vehicle,design requirements of the loading system to satisfy simulation static load,alternating load and partial load test are put forward,and the hydraulic schematic diagram is designed The loading structure of different pavement analog plates that can be changed is designed.And an integrated valve block and corresponding connecting pipe are designed.According to the principle diagram,the main components are calculated,analyzed and selected.Secondly,the mathematical model of the loading system is established,and the load characteristics of the system are obtained through experimental analysis.The influence rules of the key parameters of the system are obtained by simulation analyses.According to the actual working conditions of the system,the model is simplified properly,the forward and reverse model of the system are established and the model is normalized to form the system mathematical model.The relationship between the tire stiffness and the deformation quantity and the relationship with the excitation frequency are obtained through the experimental study.The mathematical model of tire stiffness is obtained through experimental fitting,and then the Simulink simulation model is established to analyze the accuracy of the model and the influence rules of parameters.Then,aiming at the precise control of the loading system,the control precision of the loading system is improved by the particle swarm optimization(PSO)algorithm tuning PID,common sliding mode control and integral sliding mode control.Based on particle swarm optimization(PSO)and ITAE performance index(PSO),the PID parameters are adjusted.The frequency response of PID control is slow under high frequency input signals.Therefore,a ordinary sliding mode control is designed based on the model.However,the ordinary sliding mode control has a certain system vibration.In order to further improve the control precision,the integral sliding mode controller is designed.Finally,a steering loading system is built,and the feasibility and effectiveness of the control strategy are verified by experiments.According to the designed loading system,the mechanical parts,hydraulic parts and electrical parts of the system are built,and the results of the three different loading conditions are verified by experiments.The effectiveness of the particle swarm optimization(PSO),ordinary sliding mode control and integral sliding mode control is verified by experiments and comparison with the simulation.The innovation of this paper lies in the design and construction of a steering loading system including mechanical structure,hydraulic system and electronic control part,which is helpful to the research and test of the steering performance of heavy vehicle.On this basis,a system model is established and the key parameter of the model,the tire stiffness,is studied.Based on the established mathematical model,a sliding mode controller is designed to achieve an effective control of the system.