Trajectory Tracking Control Of Four-wheel-independent Drive High Clearance Unmanned Sprayer

Autonomous navigation and collaborative operation of agricultural machinery are the inevitable trend of large-scale agricultural production in the future.As an important paddy field fertilization,pesticide application and plant protection machinery,it is of great practical significance to study the autonomous navigation control and multimachine collaborative control of high clearance sprayer to improve the operation efficiency and quality.The characteristics of high gravity center and narrow wheel of high clearance sprayer lead to sideslip inevitably when it works in muddy wet paddy field,which makes the motion characteristics of the sprayer have strong nonlinearity.Cooperative operation of agricultural machinery requires unmanned agricultural machinery not only to improve the lateral path tracking performance,but also to ensure the safe longitudinal distance between the front and rear vehicles.This paper aims to improve the trajectory tracking control performance of four-wheel independent drive high-altitude gap sprayer.The main research work is as follows :1)An autonomous navigation control system for an unmanned sprayer was developed.Taking 3WPZ-500 four-wheel independent drive high clearance sprayer as the research object,the hardware design and transformation of autonomous navigation control system of unmanned sprayer are carried out,and the software platform of autonomous navigation control system of unmanned sprayer based on ROS2 is developed.2)Kinematics model of sprayer.The steering kinematics model of the sprayer was established based on the geometric principle;referring to Ackerman steering principle,the nonlinear kinematics model of the sprayer under ideal conditions is established.Based on the kinematic velocity constraint and geometric constraint,the parameters that can represent the sideslip effect are added to the ideal kinematic model as unknown disturbances,and an improved kinematic model that can accurately describe the motion law of the sprayer under sideslip condition is established,which lays a foundation for the research of trajectory tracking control.3)The trajectory tracking control algorithm of sprayer is studied.Based on the established ideal kinematic model of the sprayer,the pose error model of the trajectory tracking error is obtained.Combined with the nonlinear control theory,the trajectory tracking control algorithm of the sprayer under ideal conditions is designed by using the backstepping method,and the system simulation and analysis under ideal conditions and sideslip conditions are carried out respectively.4)The trajectory tracking control algorithm of sprayer in the case of sideslip is studied.Based on the backstepping control strategy,a robust adaptive control algorithm is designed based on the improved kinematic model,and the above two trajectory tracking control algorithms are simulated and analyzed under ideal conditions and sideslip conditions respectively.5)Field test of sprayer autonomous navigation control system.The trajectory tracking experiments were carried out in the cement hard pavement with ideal conditions and the muddy paddy field prone to sideslip,respectively,to verify the practicability and stability of the autonomous navigation control system of the sprayer and the feasibility and effectiveness of the designed trajectory tracking control algorithm.