Research On Modeling And Control Of Intelligent Electro-hydraulic Steering System For New Energy Bus

New energy vehicles and smart cars are the development direction of automotive technology,and the development of new energy smart buses is of great significance.The new energy smart bus can realize human-machine interaction,unmanned driving,and intelligent control of steering.At present,the electro-hydraulic power steering system widely used in new energy buses cannot realize intelligent steering and has high energy consumption,which has become the bottleneck of its intelligence and energy saving.Therefore,it needs to be upgraded and modified.The subject takes the intelligent electro-hydraulic steering system of new energy buses as the research object.On the basis of the existing steering system,a motor-assisted power assist system and an accumulator hydraulic device are added to realize the intelligent and energy-saving steering system.Through the intelligent electro-hydraulic steering system Simulation model establishment,test bench construction and hardware-in-the-loop test verify the feasibility of the design scheme.The subject is based on the National Key Research and Development Program(2017YFB0103903)sub-program project and the National Natural Science Foundation of China(51675257)for research.The main research content and methods are as follows:(1)Establishment of simulation model of intelligent electro-hydraulic steering system and new energy busAccording to the existing electro-hydraulic power steering system,the design scheme and working principle of the intelligent electro-hydraulic steering system for new energy buses are given.According to the force and working conditions of the intelligent electro-hydraulic steering system,the mechanical structure,hydraulic part,hydraulic circuit and rotary valve structure are analyzed and the model is built using AMEsim software.After that,Trucksim software and Matlab/Simulink software were used to build a new energy bus intelligent electro-hydraulic steering system simulation model,and to control and process the accumulator,solenoid valve and resistance torque.(2)Selection and simulation analysis of key components of the intelligent electro-hydraulic steering system for new energy busesBased on the demand of 8098 recirculating ball hydraulic power steering,the key components:gear pump,gear pump drive motor,accumulator,etc.parameters are calculated and selected,and the double torsion bar of the intelligent electro-hydraulic steering system is analyzed through simulation analysis.The stiffness is matched and selected.By comparing and analyzing multiple groups of different torsion bar stiffnesses,a group of more appropriate upper and lower torsion bar stiffnesses is selected.Import their respective parameters into the new energy bus simulation model,and verify the feasibility and energy saving of the smart electro-hydraulic steering system through simulation.(3)Control strategy of auxiliary motor and gear pump drive motorAccording to the different forms of assistance provided by the auxiliary motor and the gear pump drive motor,the control strategy between the two is designed.Among them,through mathematical modeling of permanent magnet synchronous motor,it is analyzed that the auxiliary motor adopts vector frequency conversion—I_d=0 control can make the motor output a relatively stable torque,so as to directly provide assistance for the steering system;while the gear pump drive motor uses weak Magnetic control-negative i＿d compensation method to increase the maximum speed of the motor.(4)Intelligent electro-hydraulic steering system bench construction and hardware-in-the-loop testBuild a new energy bus intelligent electro-hydraulic steering system bench and introduce its composition and working principle.In order to verify the intelligence and energy saving of the intelligent electro-hydraulic steering system of new energy buses,the automatic steering test and auxiliary steering test of the vehicle are designed to carry out hardware-in-the-loop tests.Finally,the test results show that the intelligent electro-hydraulic steering system of new energy buses is at a certain level.To a certain extent,it has better intelligence and good energy-saving characteristics.