Research On Local Path Planning And Tracking Control Methods For Tractor-Implement Systems

Intelligent tractors are essential key technologies in modern agricultural production,providing precise operation methods and efficient energy utilization,which have significantly transformed agricultural production.This paper takes tractor-implement systems as the research object and investigates the local path planning and tracking control methods of the systems.The main research contents are as follows:(1)This paper studies the local path planning problem of tractor-implement systems in complex environments and convert it into a nonlinear programming problem for solving.Considering the large number of constraint conditions involved in the nonlinear programming problem,we first simplify the problem using adaptive homotopy algorithm in MATLAB environment.Then,we use the AMPL(A Mathematical Programming Language)mathematical modeling language in MATLAB environment to solve the problem.Simulation results show that the method can effectively complete the local path planning task for the systems.(2)This paper studies the path tracking control methods of tractor-implement systems,which includes two parts:(1)The research on tractor path tracking control methods.Considering the lateral tracking accuracy of the tractor and the lateral force requirements of the towing implement,a dual-objective joint control method that takes into account both the lateral tracking accuracy of the tractor and the lateral force of the towing implement is proposed.(2)Research on the towing implement tracking control methods.By analyzing the trajectory error generated by the towing implement during curved operation,an error compensation method suitable for implement operation during curved operation is proposed.This method can obtain the tracking reference point coordinates of the tractor based on the known coordinates of the expected path trajectory points of the implement.The tractor tracks the reference point to reduce the path tracking error of the implement.Based on the Car Sim and MATLAB/Simulink joint simulation platform,the aforementioned tracking control methods are analyzed and the effectiveness of the proposed methods is verified.(3)To further verify the effectiveness of the designed path tracking control methods,an autonomous driving system for a wheeled electric tractor is designed,including hardware and software design for environment perception,decision-making control,and actuator control.The specific content includes the selection of hardware systems and the design of the underlying interface software system.(4)A vehicle test platform is established and path tracking tests are conducted.A Beidou data acquisition software based on Lab VIEW is designed for real-time recording of tractor position information.Considering the accuracy error problem of the Beidou receiver,the Lab VIEW acquisition software and the drip method are combined during the test.The tractor’s trajectory is analyzed using the data recorded by Lab VIEW,and the lateral position deviation of the tractor is directly measured using the drip method.The test results demonstrate the effectiveness of the adopted tracking control method.