Design And Experimentation Of An Electro-hydraulic Monitoring System For Hitching Tillage Depth Based On Angle Measurements

The soil in the agricultural areas in the middle and lower reaches of the Yangtze River is sticky and humid,and the surface flatness is poor due to machine rolling,and the tillage depth is unstable during farming.In view of the above problems,this paper studies a monitoring method of tillage depth based on the pitch angle of the tractor body and the rotation angle of the lifting arm of the suspension device.The system is mainly composed of a tillage depth detection system,a tillage depth control system and a tillage depth execution system,which can preset the tillage depth value and display the real-time tillage depth.The angular displacement sensor in the tillage detection system measures the rotation angle of the lifting arm of the suspension device,and the body inclination sensor measures the tractor tilt angle in real time under different surface flatness;the tillage depth control system sends electrical signals to the tillage execution system based on the detection system feedback in real time.The electromagnetic proportional reversing valve controls the angle of the lift arm to precisely adjust the tillage depth to the preset value.The main research contents are as follows:(1)In order to rationally design the tillage electro-hydraulic monitoring system,the selection of hydraulic components and the design,manufacture and assembly of tillage control devices were carried out.The detailed structure and working process of the conventional tractor hydraulic suspension system are analyzed,the overall structure and working principle of the tillage depth electro-hydraulic monitoring system are determined,the hydraulic suspension system oil circuit is designed,the electromagnetic proportional directional valve is determined,and the SP12-20 electronic proportional valve is selected.To control the direction,the reversing valve has an independent oil return port,which can directly connect the reversing valve to the fuel tank.The arrangement of the device was researched and analyzed,and the electronically controlled hydraulic suspension system was modified on the Dongfanghong LX954 tractor.(2)The working principle of the tillage depth adjustment of the mechanical control hydraulic suspension system is analyzed,and the automatic tilling depth detection system is determined to detect the lifting arm angle of the suspension device and the pitch angle of the tractor body as the target parameters,and analyze the attitude when the suspension device is connected to the rotary tiller.The geometric relationship between tillage depth and angle is established,and the tillage depth detection model is constructed.The angle displacement sensor and the tilt angle sensor are used to measure the rotation angle of the lift arm and the change of the tractor body pitch angle to determine the tillage depth indirectly.Completed the design and selection of angular displacement sensor and tilt sensor.(3)Combined with the working principle of the tillage depth electro-hydraulic monitoring system,in order to meet the closed-loop control requirements of the monitoring system,a positional PID control algorithm is used in the monitoring system to adjust the cultivation depth.The hardware structure of the controller of the tillage depth electro-hydraulic monitoring system is analyzed,and the core part is determined to be the STC89C52 RC single-chip microcomputer to realize the design of the overall circuit of the monitoring system.The principle diagram of tillage depth control is designed,the program programming of tillage depth electro-hydraulic monitoring system controller is completed,and the single-chip microcomputer and its peripheral electronic components are simulated and debugged.(4)In order to test the response time of the automatic tillage detection system and the hydraulic execution system to the PID control signal,the physical model of the tractor suspension tillage electro-hydraulic monitoring device was established through Simulink software for simulation test.The simulation results show that after setting the target tillage depth,the tillage depth electro-hydraulic monitoring system runs smoothly for 0.6s,and the poor local surface flatness causes the tractor to raise the front of the tractor by5°,and the system can quickly adjust the three-point suspension system to keep the tillage depth stable.The adjustment time is about 0.2 s.The simulation verified that the tillage depth monitoring system can quickly respond to the tillage depth setting value.When the local surface flatness is poor,it can still be adjusted in a short time to meet the basic requirements of tractor tillage depth control.(5)In the field experiment,in order to verify that the hydraulic suspension system controlled by the tractor suspension machinery was used for field rotary tillage operations,the tillage resistance fluctuates greatly,and the conventional force adjustment method is difficult to maintain its tillage depth evenly.First,the traction force measurement test of the tractor rotary tillage operation was carried out.The tractor suspension machinery was used to control the hydraulic suspension system for field rotary tillage operation.The traction load sensor was installed at the left and right suspension drop-down rods and upper rods of the three-point suspension.Real-time monitoring of changes in traction on the rear suspension of the tractor.The test results show that during the rotary tillage operation,the values of the traction load sensors on the rear suspension device vary greatly,indicating that the rotary tiller operation has large fluctuations in the tillage resistance,and the force adjustment method is difficult to maintain the stability of its tillage depth.The accuracy test of the automatic tillage depth detection system is adopted,and the system can detect the change in the height value of the three-point suspension drop-down rod suspension point caused by tilt,and the test result that the height is stabilized at the set value is obtained,which verifies the automatic tillage depth detection system performance.In order to test the field operation performance of the tillage depth electro-hydraulic monitoring device,the designed electro-hydraulic monitoring system and the original mechanical control system were selected for comparison experiments.The results show that using the electro-hydraulic monitoring system for rotary tillage operations,the variation coefficient of tillage depth stability is up to 4.28% in each working condition.After the experiment,the field parameters showed that the standard deviation of tillage depth and the coefficient of variation of tillage depth stability were lower than the mechanical control system,indicating that the electro-hydraulic monitoring system can improve the stability of tillage depth and achieve a good stable tillage effect.