拖拉机自动驾驶系统上线轨迹规划方法

为解决现有拖拉机自动驾驶系统上线距离较长,且在上线目标点附近跟踪误差较大的问题,提出了一种基于量子遗传算法优化的B样条理论局部上线轨迹规划方法。综合考虑最大曲率约束、起止点航向约束和最大转向角约束,把最优轨迹规划问题转化为B样条控制点参数优化问题,采用量子遗传算法对目标函数进行寻优,从而求得距离最短的可行驶上线轨迹。设计了4种典型作业工况,仿真结果表明,对于不同作业工况,算法均可通过优化配置B样条控制点得到满足约束的上线轨迹,曲率和等效前轮转角变化平缓,有利于路径跟踪控制器进行曲线跟踪控制。田间试验结果表明,针对设计的复杂作业工况,单独采用纯追踪算法的上线距离为78.6 m,基于上线轨迹规划方法的上线距离为23.7 m,且后者在上线点附近的横向跟踪误差更小。

Guided Trajectory Planning Method for Tractor Autopilot System

The existing tractor autopilot system relies on the built-in path tracking algorithm to approach a target point on the global path when the driver starts the navigation mode at any position in the field. The tracking path will produce a shock phenomenon near the target point, it will affect the path tracking accuracy, and the entire approach process is uncontrollable. In order to solve this problem, a guided trajectory planning method based on third-order B-spline theory was proposed. The trajectory with the minimum length was taken as the desired path, the maximum curvature constraint, the maximum steering angle constraint and the heading of starting goal point constraint were taken into account. Quantum genetic algorithm (QGA) was used to optimize the control points, and finally the B-spline theory was used to generate a smooth desired trajectory. Four kinds of operating conditions were tested in Matlab environment. The simulation results showed that the B-spline theory based on the QGA could be used to obtain a trajectory satisfying the multiple nonlinear constraints, and the trajectory curvature change was continuous, which was beneficial to the path tracking controller. A field test was carried out, and the results showed that the pure pursuit algorithm alone had a travel distance of 78.6m, and the travel distance based on the guided trajectory planning method was 23.7m. Compared with the existing autopilot system, the trajectory planning method based on B-spline theory was helpful to control the shape of tracking path and improve the controllability of approach process.