Research Of Electronic Hydraulic Steering System Based On The Dong Fang-Hong SG-250Tractor

Wheeled tractor is the absolutely necessary part of achieving agricultural modernization and agricultural mechanization. Because there is much dust working in the field, a steering control system used for aided driving and automatic driving on tractor was developed in this study. Meanwhile vehicle driving concerned with steering wheel, throttle, clutch, braking, shifting, etc, and each mechanism must operate coordinately. As a result, long-time driving could easily cause the drivers be tired. And for reasons like bump in driving, it could lead to occupational diseases. Especially certain circumstances which agricultural vehicles like tractors, bulldozers, mine transporters, fire trucks running on. With adverse environment, great labor intensity and large harm on drivers, it was necessary to realize automatic driving.Firstly, characteristics of the automatic steering control system on tractor were studied, system structure and function of the original tractor steering control system were analyzed. And refer to the transformation of automatic tractor steering system at home and aboard, the transformation principle and scheme of automatic steering control system was determined. Based on the structure characteristics of the DFH SG-250tractor hydraulic power steering system and requirements for automatic walking tractor, a systematically modification scheme of hydraulic system was proposed. Meanwhile, the installing space of tractor was considered, in consequence this research chose the principle of overlapped valve.Secondly, the control system hardware was designed, which included the circuits such as minimum system circuit, angular displacement sensor circuit, control circuit of proportional direction valve and solenoid directional control valve, and CAN communication circuit. Control software of steering control system based on system hardware was developed, which included the program of angular displacement sensor, control program of proportional direction valve, program of PD control algorithm and soon.Finally, to test the performance of the developed electric hydraulic power steering system, the part of the transformation system was simulated with SIMILINK co-simulation, and it took the indoor and outdoor experiments. The result showed that the electric hydraulic power steering system had the advantages of large torque, fast response speed and high steering precision.