| The development of agricultural mechanization is a critical component of modern agricultural development,and it refers to the process of using agricultural mechanization technology and equipment to complete agricultural production activities.With the continuous development of agricultural mechanization,agricultural production efficiency has been significantly improved,production costs have been controlled,labor mobility has been eased,and rural economic development has been promoted.Improving the efficiency and quality of tractor cultivation in diverse levels of flatness fields is of great significance to the development of modern agriculture.In this thesis,an adaptive depth control system based on radar prediction is proposed,which solves the problem that the tractor cannot adaptively adjust the depth according to the height changes of the cultivated farmland on slopes.The thesis takes a 1304-wheeled tractor as a prototype,retains the double-acting hydraulic cylinder on the original prototype,and based on this,designs a hydraulic circuit suitable for the adaptive depth control system.Based on the double-acting hydraulic cylinder on the prototype,the specifications of other key hydraulic components and the design of the integrated valve block are determined.In terms of control strategy,the attitude of the tractorimplement unit is analyzed,the relationship between the swing arm angle of the suspension and the cultivation depth of the implement is determined,and a mathematical model of depth control is established.An angle sensor is used to indirectly obtain the cultivation depth by detecting the swing arm angle,and a radar sensor is used to scan the height of the slope in front of the vehicle.According to the measurement results,the suspension is pre-adjusted for cultivation depth,so that the implement can make corresponding adjustments before passing through the slope,and the change in cultivation depth caused by the change in the pitch angle of the vehicle body is adjusted by detecting the pitch angle of the tractor body with an attitude angle sensor.According to the working principle of the adaptive depth control system,a fuzzy PID control algorithm is used for depth adjustment of the adaptive control system.To improve the measurement accuracy of the sensor,a Kalman filtering algorithm is used to eliminate the measurement error of the sensor.The hardware structure of the adaptive depth control system is designed,and STM32F407 is used as the control core to complete circuit design and welding.The software writing and debugging of the adaptive depth control system are completed according to the control strategy and hardware circuit.A simulation model of the tractor suspension adaptive depth control system is established using Simulink software to verify the accuracy of the adaptive depth control system adjustment.The simulation results show that when the pitch angle of the tractor changes by10°,the system can cquickly control the depth to reach the set value ithin 1.1s.The simulation verifies that the adaptive depth system can still adjust quickly and keep the depth stable at the set value when working on uneven terrain,which meets the basic requirements of tractor depth control.A field test was conducted on a prototype for the depth-adaptive control system.The prototype was driven at a constant speed on a sloping test field,and the height changes of the field were scanned using a radar sensor.The depth of cultivation was indirectly obtained through an angle sensor.Four different working conditions were set with different vehicle speeds and cultivation depths.It was found through the analysis of experimental data that the maximum coefficient of variation of cultivation depth stability was 7.48%,which was observed in the working condition with a vehicle speed of 0.97 m/s and a target cultivation depth of 100 mm.It was observed that the coefficient of variation of all four working conditions was over 10%,which met the agronomic requirements.It was concluded that the depth-adaptive system can improve the stability of tractor cultivation depth and has a good cultivation depth stability effect. |
