Design And Study On Electro-Hydraulic Loading System Of Tractor's Hitch Test-Bed

With the rapid development of elctronics, computer, artificial intelligence and other advanced technologies in recent years, the hydromechatronics technologies are applied to the tractors, pushing tractors'development to intelligence. At present, the Electro-hydraulic hitch is replacing the traditional hydraulic hitch, however, its research is still in the primary stage. In order to research and develop the hitch's control strategy, shorten the development cycle and reduce the development cost, it's inevitable to design a loading test-bed to simulate the soil resistance exerting to the plough body systematacially.Kinds of loading systems appear at home and abroad presently, they have different functions and they are focused on transmission, chassis and steering of vehicles and tractors' and haulage motors'steering. Their aims are to meet key mechanism's research and design requirements, and to test relative characters. In the test system area of tractor's hitch test-bed, majority are for testing the lifting capacity of tractor's hitch, and minority are devoted to design and research the test-bed for loading system. Because of the current situation, hitch's loading system is researched in this article, based on the electro-hydraulic hitch test-bed. The main research content reads as follows:Firstly, it has to compare the common loading methods and applicable places, and analyze their merit and demerit. According to tractor's real working conditions, it's decided to use electro-magnetic proportional relief valve to load. Design parts include machinery, hydraumatic and electronic control. Besides that, an electro-hydraulic hitch loading test-bed is needed to build, and select the suitable hydraulic elements and sensors to install.Then, it's necessary to analyze theoretically and calculate the soil resistance when the tractor is ploughing. The test method for spatial three-component soil resistance is to paste strain gages to the hanging beam as bridge circuits. The field test result can be used to verify the theoretical analysis, and conclude soil resistance's change along with different speeds and tilling depth.After that, AMESim-Simulink joint simulation is used to analyze the hitch loading system. On one hand, it can check whether the loading system is reasonable or not. On the other hand, the control strategy can be made sure by the means of simulation test. As the result shows, the classical PID control strategy can not only keep the loading system accurate and stable, but also make the system quick response, adaptive and high precision. The method meets the requirements of electro-hydraulic hitch's research and performance test.At last, mixed signal ISP FLASH micro controller of singlechip C8051F040 is made as ECU controller, and design the hardware circuits and software procedure. Based on the loading test-bed, some bench tests are carried out. Calibration of sensors and electro-magnetic proportional relief valve should be done ahead. Some signals, such as constant, step and ramp, are inputted to simulate the soil resistance bearing on the working plough body under tractor's different working conditions.