Design And Research Of Independent Steering System For Four Wheel High Clearance Operation Vehicle

The high-stalk crops are corn and tobacco in Henan mainly,spraying and topping in the middle and late stages are important for its quality and yield.The stalk diameters of corn and tobacco are relatively high,and tobacco is mostly grown by hand and have varies ridge distance,the traditional vehicles are difficult to enter the block because it has a fixed track,so resulted in labor intensity and low efficiency in the middle and late management period.In addition the traditional management vehicle' steering model is single and steering is not flexible.Aiming at the above problems,this paper designs a four-wheel independent steering system for high-gap operation vehicle that can adjust the wheelbase,the actuator design of the independent steering system,the design of the steering hydraulic system,the determination of the control scheme of the steering hydraulic system and the bench scale test of the steering are discussed in turn and the main tasks are as follows:Firstly,the overall structure of the operating vehicle was designed according corn and tobacco planting mode.The operating vehicle is mainly composed of a frame,an independent steering system,a walking system and so on,and can enter the corresponding block for operation smoothly.The design of the four-wheel independent steering structure is mainly discussed which adopts a four-bar linkage structure,and can match the variable pitch of the vehicle between 1.7~2.1m.The front wheel steering,four-wheel steering,oblique deflection steering and other steering modes all can be achieved.The mechanical and dynamic analysis of the designed steering mechanism was carried out by establishing a mechanical model,and obtained the thrust mathematical expression of the steering cylinder.With the aim of minimizing the output thrust of the steering cylinder,steering hydraulic cylinder' position was optimally analyzed with Adams software,and the better position of the mounting position of the hydraulic cylinder end were determined.Secondly,the steering hydraulic working system of the vehicle was designed.The working principle of the steering hydraulic system was mainly drawn and analyzed;the core elements in the hydraulic system were calculated and selected.At the same time,combining the steering function to be achieved,the basic idea of controlling the rotation angle of the vehicle by controlling the displacement of the hydraulic cylinder is determined,and the relationship among the steering wheel angle,the displacement of the hydraulic cylinder and the rotation angle of the wheel is analyzed,and a proportional steering hydraulic control scheme is designed.The results of the AMESim software simulation model showed the availability of the control system,which steering hydraulic cylinder can respond quickly to the input signal and achieve the controllability of the steering system.Thirdly,the electronic steering system of the vehicle was designed and selected the hardware of the electronic control system such as the controller,encoder and so on.According to the steering function of the operation vehicle,the steering circuit and the variable distance electrical circuit are designed.The logic sequence of the steering control was analyzed in conjunction with the designed electrical circuit,and given part of the steering system program and control flow chart.Finally,the front wheel steering test bench of the steering system was built.The front steering was verified through the built-up steering bench.Given a fixed steering angle in the test,the hydraulic cylinder can reach the desired position well and the maximum error can be maintained within ±1.2mm,the number of oscillations of the hydraulic cylinder at the ideal position is less at the same time.When a continuous steering signal is given,the hydraulic cylinder has relatively good response and following accuracy,although the control accuracy is slightly lower than the fixed signal,it basically meets the expected turning requirement.