The Design Of Tractor Automatic Steering System And Research Of Positioning And Navigation

Precision agriculture is the development direction of modern agriculture,can greatly improve the efficiency of agricultural production.Tractor automatic navigation technology is one of the key technologies for implementing precision agriculture,widely used in farming,sowing,fertilizing,spraying,harvesting and other agricultural production processes.Tractor automatic steering system transformation,position measurement method,navigation path tracking control algorithm and so on are the key technologies to realize the automatic navigation of the tractor,and it is of great significance to carry out the research on the related technologies.Based on the introduction of the related technologies of automatic agricultural machinery navigation,this paper mainly focuses on the automatic steering system of the tractor,the method of agricultural machinery positioning and the navigation path tracking control algorithm.Firstly,propose the steering system automatic steering reconstruction scheme for the characteristics of the tractor steering system,and design the automatic steering control core unit-the automatic steering control valve group.Analyze the static and dynamic characteristics of steering control system by establishing the mathematical model of hydraulic steering system.Build AMESim simulation model of the steering system to analyse the characteristics of the system.Design PID steering control method to improve the accuracy and response speed of the automatic steering system,to meet the requirements of automatic steering system for tractor automatic navigation.And then,considering a various of positioning methods,apply differential enhanced satellite positioning method to tractor automatic navigation.Research pure pursuit path tracking,especially pure pursuit path tracking of straight line in cartesian coordinate system and pure pursuit path tracking of constant curvature curve in polar coordinate system,and set up the path tracking model.Set up simplified two wheel vehicle motion models under the cartesian coordinate system and the polar coordinate system respectively for path tracking simulation.Build Simulink model,and carry out simulation analysis and optimization of straight pursuit model and curve pursuit model.Finally,reform the real tractor steering system based on automatic steering reconstruction scheme,and perform steering tests and field navigation tests.The results showed that the steering order perform quickly and accurately and the path tracking error is less than 5cm,which can meet the requirements of agricultural production for automatic navigation of tractors.Automatic steering control valve group designed for tractor steering system automatic steering reconstruction is of important reference significance for the automatic steering reconstruction of agricultural machinery and other machinery which steering system drived by hydraulic power.In addition,the research of pure pursuit path tracking of constant curvature curve in polar coordinate system is of a certain reference value for curve line tracking.