Design Of Navigation Control And Task System For High Clearance Sprayer In Paddy Field Based On GNSS And AHRS

Navigation and automatic operation of agricultural machinery is an inevitable trend of large-scale farmland production.High Clearance Sprayer machine,as an important plant protection machine,the research of its automatic navigation operation system is of great practical significance to improve the efficiency and quality of spraying operations Due to High Clearance Sprayer machine has high center of gravity,narrow tyre,and widely spraying swath,the accurate movement state information is very difficult to obtain.The wheel angle control delay causes a significant disturbance to stability of the navigation control system,and the wheel sideslip make the spray machine movement characteristics with strong nonlinear.These poses a challenge to realize high precision navigation path tracking control.To solve the above problems,obtaining methodes of vehicle motion parameters based on integrated navigation positioning system are presented,the low latency wheel angle tracking control technology is designed based on decoupled the nonlinear electro-hydraulic steering system,and the path tracking control method based on nonlinear kinematic model is developed.In the end,the High Clearance Sprayer automatic navigation operation system was developed and the test in paddy field was carried out.The main research work is as follows:1)Study on vehicle motion parameter acquisition method based on GNSS and AHRS combined navigation and positioning system.Through the study of vehicle dynamics,kinematics model and vehicle side characteristics,the nonlinear kinematics model of the sprayer with parameters such as the previous wheel position,vehicle heading Angle,front and rear wheel track angle,running speed and wheel angle was determined.By analyzing the parameter composition of the model,the integrated navigation positioning system with global differential navigation satellite system(RTK-GNSS)and attitude reference system(AHRS)as the main sensors were determined,and the parameter acquisition scheme with coordinate projection and transformation and kalman filtering as the main data fusion methods were designed.The stability and accuracy of the integrated navigation positioning system were verified by evaluating the coincidence degree between the simulation trajectory and the real trajectory in the field.2)Research on wheel angle tracking controller based the decoupled of electro-hydraulic steering nonlinear system.In order to realize the electrification control of sprayer steering,the electric-hydraulic steering control system is designed on the basis of the original hydraulic system.Based on Newton's second law and fluid continuity theory,the dynamic characteristics of the electro-hydraulic steering system are studied and the nonlinear system model is established.Decoupling the nonlinear system model into three parts: dead zone and saturation,nonlinear gain and gap characteristics.A dead zone compensator,a PD steering controller and the dynamic attenuation gap compensator are designed.Through the test under paddy field verified that the method can obtain the low-delay wheel angle tracking control between 200-300 ms.3)Research on the path tracking controller of sprayer in paddy field.Based on the nonlinear kinematics model of the sprayer,the linear model of path tracking deviation is obtained by adopting the Frenet frame relative coordinate system,the linear chain system construction method and the state variable transformation method,and the path tracking controller is designed based on LQR method.In order to reduce the delay of track tracking error correction caused by wheel angle control lag,a dead reckoning method and a decision wheel angle prediction method are proposed based on the combination of kalman filter and path tracking control law.During a straight path tracking test in paddy field,the prediction data showed that error of 200 ms forecast decision wheel angle is less than 1 °.In order to eliminate the static error of the system and restrain the disturbance of path tracking control in paddy field,an integrator with variable-speed integral and integral maintenance and anti-saturation characteristic is designed.So,a path tracking control method is designed by the composed of path tracking control law,vehicle motion state estimator and integrator is designed.4)Development of sprayer automatic navigation operating system and experimental verification in paddy field.The information acquisition and data fusion unit,the wheel Angle tracking control system and the path tracking controller are integrated through the machine-electric-hydraulic transformation and the software and hardware system design.The integrated operation control system and wireless monitoring terminal equipment are designed to realize automatic navigation of spray machine.In order to verify the stability and control accuracy of the system,the automatic navigation control operation test was carried out at the operating speed of 1.35m/s in paddy field.Druing automatic navigation control and operation,the path tracking control process is stable and turning at row-turn is smoohthly,no overshoot in the initial stage of path tracking and stop operation timely after completed the work.The accuracy of path tracking is satisfactory,the maximum path tracking error is 12.8 cm,while the maximum deviation standard deviation is 3.2 cm,the minimum standard deviation is 2.4 cm.Data show that the navigation operation system designed in this research can meet the spray application requirements in paddy field.