| Bulldozer, one of the most important machines in mechanical engineering, is widely used in construction, railway building, open mining, national defense and so on. Because of its atrocious working condition and high-strength operation, manual operation with bar linkage is used from mechanical transmission to dynamic transmission. The operation way has problems like high operation force, installation space, inconvenient adjustment and maintain, which badly influence the stability, maintainnance, security and duration. The paper aims at electro-hydraulic steering control system for the PD220Y bulldozer by Shanghai Pengpu Machine Corporation. Not only all the problems are solved by the system, but also the performance is greatly improved. At the same time, integration of shifting and veering is worked on.Transmission system of PD220Y bulldozer is detailedly analyzed, including the output characteristic of engine and hydrodynamic torque converter, gear-box, clutch, and entire car. Function requirement and evaluating indicator are raised, according the mechanical, electronic and hydraulic integration method. Immunity and reliability are also discussed.The electro-hydraulic steering operation system for bulldozer is made up of four parts: signal input, ECU, signal output and hydraulic actuators. Signals from machine handle and whole car is put into ECU, and, indicators and electromagnetic valves are controlled by ECU.Ideal oil pressure curve of transmission process is analyzed, and design specification of hydraulic system is raised. 6WG180F valve is selected as the basic, and its performance parameters are adjusted. With the help of 3D software, mechanical structure of the valve is redesigned. The veering hydraulic system is also designed.Design of hardware and software of ECU is done, and basic function and performance of the control system is tested with the designed data acquisition system on the bedstead.
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