Research On All Wheel Hydraulic Power Steering System Of Wheel Excavator

At present,wheeled excavators are in a major position in the world’s earthwork machinery.Because the wheeled excavator has the advantages of fast movement speed,long-distance transfer and rapid replacement of various traditional operation units,it is widely used in earth excavation and material handling.The steering system of the vehicle is an important part of the vehicle.When the driver wants to turn the vehicle,he will turn the steering wheel to change the direction of the vehicle,so as to maintain a safe and stable driving condition.Since wheeled excavators are mostly used in municipal projects with small space,it is inevitable to redesign the hydraulic system with small turning radius,fast response and high stability,so that the wheeled excavator can turn all wheels,so as to work in small space terrain and complex working conditions.The research object of this paper is the hydraulic power steering system of wheel excavator.The motion characteristics of wheel excavator and the selection and design of hydraulic system are analyzed,and a design scheme of all wheel hydraulic power steering system of wheel excavator is proposed.The specific research contents and methods are as follows:(1)According to the movement law of wheel excavator during steering,firstly,the stress of wheel excavator tire is analyzed,then the nonlinear eight degree of freedom vehicle dynamics model of wheel excavator is established,and then the kinematics of wheel excavator under three different steering modes of front wheel,rear wheel and all wheel is analyzed,and the corresponding mathematical model is established.The working principles of three key components in the hydraulic power steering system of wheeled excavator-load sensitive variable pump,load sensitive proportional multi-channel control valve and spiral rotating oil cylinder are analyzed,and the mathematical models are carried out respectively to explore the load sensitive circuit and its working mechanism under three different rotation modes of front wheel,rear wheel and all wheel of the rotary control system.(2)The model of hydraulic power steering system of wheel excavator is built in AMESim software.AMESim simulation is carried out for the steering system under various working conditions,and the dynamic response of the system is analyzed.Then,the control strategy combining master-slave control and PID control is adopted to analyze the influence of the control strategy on the characteristics of all wheel hydraulic power steering system of wheel excavator.The main research contents and conclusions of this paper are as follows:According to the model of the built all wheel hydraulic power steering control system of the wheel excavator,the simulation is carried out without the combination of master-slave control and PID control strategy and with the combination of master-slave control and PID control strategy.Without the combination of master-slave control and PID control strategy,the four spiral rotation cylinders begin to move at 0.2S during all wheel steering,The steering amplitude of the inner left front and rear spiral cylinder is greater than that of the outer right front and rear spiral cylinder,which conforms to Ackerman steering principle.With the combination of master-slave control and PID control strategy,during all wheel steering,the four spiral rotation cylinders begin to move at 0.1s,and the steering amplitude of the inner left front rear spiral rotation cylinder is greater than that of the outer right front rear spiral rotation cylinder,which conforms to Ackerman steering principle.The overall response time,steadystate error and other dynamic characteristics of the system meet the standards of construction machinery and the system design requirements.The results show that the control strategy combining master-slave control and PID control is adopted to optimize the system.The overall response time,steady-state error and other dynamic characteristics of the system not only meet the standards of construction machinery,but also improve the synchronization by 0.1 seconds compared with the original system,meeting the design requirements of the system.