基于优化人工势场法的插秧机绕障策略研究

Obstacle Winding Strategy of Rice Transplanter Based on Optimized Artificial Potential Field Method

针对水田中存在的壕沟、田埂、石块、电线杆等障碍物使得插秧机无法保证作业连续性和插秧直线性等问题,设计了基于优化人工势场法的插秧机绕障路径规划策略。通过增加插秧机实时位置与目标作业点的相对距离作为判断条件来动态改变势场大小,同时设立了虚拟局部目标点来弥补传统人工势场法目标点不可达和局部最小点的算法缺陷;将插秧机简化为二轮车模型,建立插秧机转向系统数学模型,得出插秧机速度、行驶航向角和前轮转角表达式,以横向偏差与航向偏差作为评判路径优化效果的因素。转向控制器以复合模糊PID算法控制插秧机的转角,不断减小理想前轮转角与实际转角的偏差,实现转角最优化;采用超声波传感器实时检测道路障碍物并结合RTK-GPS实时更新位置坐标,设计出插秧机绕障转向控制策略。通过Matlab对优化的人工势场法的避障路径控制策略进行仿真,仿真结果表明,当障碍物不在影响范围内,插秧机直线追踪的最大横向位置偏差为5 cm,平均偏差约为2 cm,最大避障横向偏差小于0.5 m,优化后的算法具有较好的控制精度,可避免目标点不可达的问题。基于洋马VP6E插秧机作为实验平台进行了实车实验,实验结果表明,当插秧机以速度0.5、1.0、1.5 m/s行驶时,左侧绕障的最大横向偏差均不大于1.2218 m,航向偏差最大值为30.1491°,绕障前后直线追踪的平均横向偏差为0.025 m,平均航向偏差为3.12°;右侧绕障的最大横向偏差均不大于1.2459 m,航向偏差最大值为25.2294°,绕障前后直线追踪的平均横向偏差为0.023 m,平均航向偏差为3.36°,所设计的避障方法可满足插秧机在农艺作业过程中的避障要求,具有很好的可行性与鲁棒性。

Aiming at the problems that the obstacles such as ditches,ridges,stones and electric poles in paddy fields make the rice transplanter unable to ensure the continuity of operation and the straightness of rice transplanting,a path planning strategy for rice transplanter around obstacles based on optimized artificial potential field method was designed.The relative distance between the real-time position of the transplanter and the target operation point was added as the judgment condition to dynamically change the size of the potential field.At the same time,a virtual local target point was set up to make up for the algorithm defects of the target point unreachable and local minimum point of the traditional artificial potential field method.The transplanter was simplified into a two wheeled vehicle model,the mathematical model of the steering system of the transplanter was established,and the expressions of the speed,heading angle and front wheel angle of the transplanter were obtained.The lateral deviation and heading deviation were used as the factors to judge the effect of path optimization.The steering controller used the compound fuzzy PID algorithm to control the rotation angle of the transplanter,continuously reduce the deviation between the ideal front wheel rotation angle and the actual rotation angle,and realize the optimization of the rotation angle.Using ultrasonic sensor to detect road obstacles in real time and RTK-GPS to update the position coordinates in real time,the steering control strategy of rice transplanter around obstacles was designed.The obstacle avoidance path control strategy of the optimized artificial potential field method was simulated by Matlab.The results showed that when the obstacles were not within the influence range,the maximum transverse position deviation of the straight-line tracking of the rice transplanter was 5 cm,the average deviation was about 2 cm,and the maximum obstacle avoidance transverse deviation was less than 0.5 m.The optimized algorithm had good control accuracy and can avoid the problem of unreachable target points.Based on Yangma Vp6 E rice transplanter as the experimental platform,the real vehicle experiment was carried out.The experimental results showed that when the rice transplanter ran at the speed of 0.5 m/s,1.0 m/s and 1.5 m/s,the maximum lateral deviation of the left side obstacle was no more than 1.2218 m,the maximum heading deviation was 30.1491°,the average lateral deviation of the straight line tracking before and after the obstacle was 0.025 m,and the average heading deviation was 3.12°.The maximum lateral deviation of the right side obstacle was not more than 1.2459 m,the maximum heading deviation was 25.2294°,the average lateral deviation of straight-line tracking before and after the obstacle was 0.023 m,and the average heading deviation was 3.36°.The designed obstacle avoidance method can meet the obstacle avoidance requirements of the transplanter during driving,and had good feasibility and robustness.