Design And Research On Hydraulic Steering-by-Wire System Of Tractor

The operated frequency of steering system is one of the highest for tractor,and the steering system performance plays a vital role in drivers operated feeling and riding stability.For traditional tractor,the fully hydraulic steering system can't change its steering sensitivity and provide the road feeling for drivers.The Hydraulic Steering by Wire System was designed by applying the X-by-wire to tractor steering system for dealing the problem.The Hydraulic Steering by Wire System abandons the mechanical structure between hand-wheel and steering wheels uses the signal to take its place,the replacement simplify the steering system structure and make it impossible to design the steering system angle ratio and force-ratio freely without decreasing the steering force.The hydraulic system makes the Hydraulic Steering by Wire System different from other Steering by Wire System with motor as power.The paper has finished the following work;Firstly,the total design of tractor Hydraulic Steering by Wire System was done.The paper designed the new steering system with the help of X-by-wire based on analyzing the shortcoming of the fully hydraulic steering system,which replaced the fully hydraulic transducer with the electro-hydraulic servo valve.The importance was the working principle and the connection between the steering cylinder and steering wheels,in addition,the main parameters and component model was determined.Secondly,the modeling and simulation work was finished for the designed steering system.The control law of the Steering by Wire System was analyzed detailedly,concluded that the system is sensitive to load and needs loop control,which was the bases for following research.The steering system was modified by making the main oil circuit pressure change from the load,at last,the system which is sensitive to load was done.The system model was built based on AMESim and Simulink software,the simulation results proves that the designed system is satisfactory.Thirdly,the control algorithm for hydraulic steering by wire System was studied.A method of variable universe two-stage fuzzy PID was studied and designed in the application of tractor hydraulic steering by wire system?Through analysis and comparison on variable universe two-stage fuzzy PID algorithm is more suitable for hydraulic steering by wire system,The detailed design of variable universe two-stage fuzzy PID controller,and the fuzzy PID and variable universe fuzzy PID control based on functional together to join the united simulation model simulation comparison test and verify,The results show that the variable universe two-stage fuzzy PID control algorithm and variable region higher control accuracy and response speed faster,so this control algorithm is chosen as the final line of hydraulic steering system is presented in this paper.Fourth,the study on the prefect steering way of hydraulic steering by wire system for tractor was done.The prefect steering angle ratio was concluded based on analyzing the tractor prefect steering way.The simulation with Two degrees of freedom vehicle model was used to prove that the designed prefect steering angle ratio can improve tractor operated easiness and stability performance.Finally,the bench test was done.bench test for Hydraulic Steering by Wire System was to examined the loop control system and control algorithm.Results show that the designed Hydraulic Steering by Wire System can meet the requirements.