Study On The Electro-Hydraulic Loading System Based On Hydraulic Steering By-Wire Test-Bed

In recent years, with the development of electronic technology used in vehicles more widely, tractors’ steering system is being transformed from traditional full hydraulic steering into the electronic, intelligent and network direction quickly. Hydraulic power steering, electronic hydraulic steering, hydraulic steering by-wire and so on appear one by one at home and abroad. Cause to the severe working environment, driving road conditions and multi-working farms, it requires more standard steering performance. As a new way to develop, hydraulic steering by-wire has to be designed efficiently and run in test bed.There are too many kinds of loading systems with different functions in markets at present. Because of agricultural machines’terrible working conditions and complicated environments, especially to tractors, test bed is immature. Besides that, there are lots of disadvantages in testing methods. Based on features of hydraulic steering by-wire, steering loading system is researched as follows:Firstly, it’s necessary to analyze loading system’s merit and demerit, bond to tractor’s actual working situations, and loading project is made sure to apply to tractor’s hydraulic steering by-wire system, namely loading system based on electronic-hydraulic proportional valve. In all kinds of hydraulic steering by-wire testing beds, single hydraulic cylinder applied to front-steering trapezium has advantages in benefit of steering structures in test bed. So loading cylinder mounted symmetrically is chosen to load resistance to steering knuckle. In addition, it includes designing hydraulic loading module and ECU module in loading system. It expounds every system’s parts and the whole loading system’s working principle at length. It needs to select the perfect types of hydraulic elements, sensors and control units.Then, it has to analyze the steering resisting torque in theory and calculate the value during tractor’s steering, also the factors which influence the steering resisting torque are analyzed in detail. Then it require to confirm the ground lateral resistance during tractor’s steering and make sure loading method of steering resistance. After that, steering must be taken placed in order to verify with the analyzed date theoretically. The result indicates that it has an error of2.5%between theory value and measured value, but the error is in a permitted range.After that, conventional control strategies applied to loading system are studied and compared. The classical PID control algorithm is used to the system, and software AMESim is used to simulate the loading system in combination with software MATLAB/Simulink. According to the result of joint simulation, it’s seen that PID control is adaptable to the system’s changes, and it can come true that controlling the tractor’s steering loading system effectively.At last, the control unit of loading system is completed on the base of loading bed. The tasks consist of designing the control system’s hardware circuit based on C8051F020and devising system’s software. When all done, some relative loading tests can be carried out on the bed.