密植果园作业机器人行间定位方法

Inter-row Localization Method for Agricultural Robot Working in Close Planting Orchard

在密植果园的果树行间,由于浓密树冠对卫星信号的遮挡,目前在开阔环境中成功应用的农业机械卫星导航定位方式存在失效问题。而单纯利用里程计在果园进行定位,又存在误差累积的难题。为此,以农业机器人驶入果树行前的初始位置点为原点,建立世界坐标系。利用激光雷达扫描作业空间中果树行两边的树干,根据圆弧聚类方法计算树干中心点,并记录在世界坐标系中。而后,在机器人运动过程中再实时检测果树树干中心点,并与先前时刻记录在世界坐标系中的树干中心点进行匹配,利用匹配结果校正里程计数据计算出的机器人位置和航向,以实现在密植果树行间对农业机器人进行准确定位。10次重复实验表明,农业机器人在世界坐标系的x和y方向上定位误差的标准差都约为0.08 m,精度能够满足密植果园作业机器人的应用需求。

Global navigation satellite system for localization of agricultural machineries has been successfully used for many years in a broad-acre environment. However, it will fail to work in a close planting orchard because navigation satellite signals are often interfered by dense tree canopies. Moreover, localization by only odometers can lead to a large accumulated error. Therefore, firstly the position of an agricultural robot before entering inter-row of the close planting orchard was taken as an original point and a world coordinate system was established. A laser radar was applied to scan trunks on the both sides of the robot and the center points of trunks were extracted through circular clustering. The position values of these center points were saved in the world coordinate system. Then during the moving of the robot, the center points of trunks detected by the laser radar in real time were matched with those which had been saved previously in the world coordinate system. Matching results were applied to correct the robot position and heading angle which had been measured with only odometers. In this way the agriculture robot was able to locate itself accurately in the inter-row of the close planting orchard. Repeated experimental results showed that the robot localization standard errors in both x and y directions in the world coordinate system were about 0. 08 m. The localization accuracy can meet requirements when the agricultural robot is applied in the close planting orchard. Moreover, the successful inter-row localization is the premise of global positioning and navigation of the robot working in the orchard.