Research On Path Tracking Control Of Agricultural Tractor Based On Second-Order Sliding Mode Control Theory

Agriculture has always been the foundation industry for China’s economic construction and development.With the continuous progress of technology,unmanned agricultural machinery’s autonomous driving system has gradually become an important technology for China to achieve agricultural modernization.The path tracking control algorithm is the core of the agricultural machinery’s autonomous driving system,with advantages such as improving operational efficiency,alleviating labor shortages,and improving the accuracy and stability of the agricultural machinery’s autonomous driving system,thus better serving agricultural production.In order to study the path tracking control system for unmanned agricultural machinery’s autonomous driving,this paper uses an intelligent small car simulated as a tractor as the experimental platform for in-depth research.The research content mainly includes:Firstly,the overall architecture of the path tracking control system is studied.Based on vehicle dynamics theory and involving vehicle state information and front wheel steering control modules,the path tracking system of agricultural tractors is mathematically modeled.On this basis,the system can be simplified in design by combining it with the analysis of agricultural machinery path tracking control requirements.By using the simplified linear model and deviation model of agricultural machinery dynamics,the motion laws of agricultural machinery during the driving process can be better understood,thus providing better support for agricultural machinery path tracking control and improving the practicality and feasibility of the system.Secondly,based on the agricultural machinery dynamic model,this study combines the sliding mode control system with the path tracking dynamic model of agricultural tractors and designs a second-order sliding mode control algorithm for agricultural machinery path tracking control,which improves the system’s dynamic response and stability.However,in practical applications,the upper bound of the disturbance derivative in traditional second-order sliding mode control is unknown,making it difficult to adjust the gain.Therefore,in order to cope with the nonlinear uncertain factors that may arise in agricultural vehicles under complex working conditions,such as wheel slip and vehicle tilt,this paper introduces adaptive control based on the second-order sliding mode to automatically adjust the gain and solve the possible chattering problem and internal model uncertainty of traditional sliding mode controllers.This improves the practical value and provides reliable technical support for automatic driving of agricultural vehicles under complex working conditions.Simulation results show that the proposed controller is feasible and effective.Finally,in order to verify the performance of the designed controller,this paper used the Carsim/Simulink joint simulation platform to build a path tracking system based on sliding mode control,and conducted simulation verification under disturbance conditions.The simulation results show that the designed second-order sliding mode controller can provide stable and accurate control inputs to the system,verifying the feasibility of its theoretical application.Based on this,the path tracking system algorithm was applied to a simulated tractor unmanned intelligent vehicle system and vehicle modification was performed.Further verification of the controller’s practical application value was conducted through a complete on-road experimental platform under disturbance conditions(such as crosswinds,road bumps,and sandy road conditions).The experimental results show that the control strategy of the sliding mode control path tracking system studied in this project can meet the precision requirements of agricultural machinery for field operation route tracking,and conforms to the standard of unmanned agricultural machinery automatic driving system in precision agriculture.In summary,the method proposed in this paper provides an effective reference for the design and engineering application of agricultural machinery path tracking systems,and can improve the performance and stability of the system,providing strong support for agricultural production.