几何路径跟踪组合算法及其农业机械自动导航应用

Integration of geometric-based path tracking controller and its application in agricultural machinery automatic navigation

农业机械自动导航是实现精准农业的有效途径,高精度路径跟踪控制是智能农机自主作业可靠性的重要保证。为提高不同路径曲率和初始误差条件下路径跟踪算法适应性,基于两种几何路径跟踪方法自适应切换提出一种几何路径跟踪组合算法。分析纯追踪和Stanley模型在U型路径跟踪中的稳态误差和收敛特性,在恒定速度下分别设置其最优几何路径跟踪参数,以跟踪误差和路径曲率为输入量设计路径跟踪方法切换逻辑,并采用往复式梭行路径对几何路径跟踪组合算法进行测试。搭建移动小车平台对所提算法有效性进行验证,跟踪结果表明当初始误差为2.5 m时,Stanley模型较纯追踪算法有更快的收敛速度,当直线和曲线路径作业速度为1.0 m/s和0.7 m/s时,纯追踪与Stanley具有相似直线段跟踪误差,但曲率突变时纯追踪和Stanley模型最大跟踪误差分别为12.0 cm及11.0 cm。路径跟踪组合算法有效减小曲率突变时路径跟踪误差,相同速度配置下梭行路径最大跟踪误差为9.0 cm,较纯追踪和Stanley分别减小25.0%和18.2%。几何路径跟踪组合算法减少前视距离和增益系数在线优化运算量与算法复杂度,可为复杂作业场景下农机自适应路径跟踪算法设计提供工程实现参考。

Agricultural machinery autonomous navigation is an effective approach to achieve precision agriculture,and highprecision path tracking control is a critical assurance for the reliability of intelligent agricultural machinery autonomous operations.To improve the adaptability of path tracking algorithms under different path curvatures and initial error conditions,a geometric path tracking combined algorithm based on adaptive switching of two geometric path tracking methods was proposed.The steady-state errors and convergence characteristics of the pure pursuit(PP)and Stanley model in U-shaped path tracking were analyzed,and their optimal geometric path tracking parameters were respectively set at a constant velocity.A path tracking method switching logic was designed based on tracking errors and path curvature as input,and a boustrophedon path was used to test the geometric path tracking combined algorithm.A mobile cart platform was built to verify the effectiveness of the proposed algorithm.The tracking results showed that when the initial error is 2.5 meters,the Stanley model had a faster convergence rate than the PP algorithm.When operating at speeds of 1.0 m/s for straight paths and 0.7 m/s for curved paths,the PP and Stanley model exhibited similar tracking errors for straight segments,but when the curvature changed abruptly,the maximum tracking errors for the PP and Stanley model were 12.0 cm and 11.0 cm respectively.The path tracking combined algorithm effectively reduced the tracking error during curvature changes,with a maximum tracking error of 9.0 cm under the same speed configuration for the reciprocating shuttle path,representing a reduction of 25.0%and 18.2%compared to the PP and Stanley model respectively.The integration of geometric-based path tracking algorithm reduced the computational load and complexity of online optimization for forward distance and gain coefficient,and thus effectively improved the adaptability of path tracking algorithms for agricultural machinery under complex soil condition.