植物根系特征与根区土壤水分高通量监测管道机器人研制

Development of a pipeline robot for high-throughput monitoring plant root characteristics and soil moisture in root zone

研究水分胁迫下的根系特征对于节水农业的发展具有重大意义。针对现有根系观测与土壤水分监测方法难以满足野外条件下根系和根区水分的同步、原位、高通量监测的不足,该研究研制了一种基于STM32芯片的管道机器人系统。系统由管道机器人、数据基站与PVC透明管道组成,通过在土壤中埋设管道机器人系统,控制机器人搭载的微距相机与土壤水分传感器在巡航时拍摄根系图像,并获取土壤水分数据。由根系图像识别分割与提取程序对图像进行畸变校正与根系识别,获取管道方向上植株的根系面积、长度与密度等特征参数。实验室条件下进行相机拍摄效果、图像畸变校正、识别与分割误差及里程轮测距误差测试,以及土壤水分传感器标定试验。测试结果表明:1)管道机器人能够清晰地拍摄到根系图像,图像畸变校正效果较好,单个像素点长度和面积分别为44μm和0.002 mm^(2),单张根系图像的拍摄范围为14.17 mm×10.60 mm;2)土壤水分传感器输出电压与土壤体积含水率之间呈现良好线性关系,决定系数R^(2)为0.990;3)自主巡航定位准确度较高,平均相对误差为1.47%。在田间条件下进行的根系生长动态监测、根系信息提取、土壤水分监测与电池续航试验表明:1)管道机器人系统能够在田间环境下高通量地拍摄根系图像,监测根系的生长动态,并进一步提取出根系长度、面积、根面积密度等特征参数;2)根区土壤水分监测较为准确,测量结果与烘干法结果平均相对误差为2.23%;3)在系统初始满电量状态下,管道机器人系统独立运行时长不少于7 d,最大巡航监测距离约为48 m。本文研制的管道机器人系统可在田间条件下实现根系特征以及根区土壤水分的原位、高通量测量,为节水灌溉与根系生长研究提供技术支持。

A root is one of the most important vegetative organs of plants.It is of great significance to explore the growth status of root under different water stress in modern agriculture.However,the existing observation of plant root are cumbersome,laborious and time-consuming.It is the high demand to meet the requirements of precision irrigation and water-saving under field conditions.In this study,a pipeline robot system was developed for the synchronous,in-situ and the high-throughput monitoring of plant root and root soil water using STM32.The system consisted of pipeline robot,data base station and PVC transparent pipeline.The pipeline robot system was embedded in the soil,where the macro camera and soil moisture sensor were carried by the robot.The root images were captured to obtain the soil moisture data while the robot cruising.Meanwhile,the robot shared the functions of autonomous timing cruise,wireless communication using command data and active return after encountering obstacles.The distorted correction,registered on plane,identified and segmented images were obtained for the parameters of the root area,length and density of the plants in the direction of the pipeline.The results of laboratory test show that:1)The pipeline robot was clearly captured the root images,indicating the excellent performance on distortion correction and plane registration.The true length and area corresponding to a single pixel were 44μm and 0.002 mm^(2),respectively,whereas,the shooting range of a single root image was 14.17×10.60 mm.The characteristic information of root was obtained using MATLAB,where the images taken by the automatic cruise of pipeline robot.The image processing operations included the image distortion correction,image preprocessing,root region recognition and segmentation,and root feature extraction.Compared with the root characteristic parameters measured by the excavation,the relative errors of the root image processing program were 12.29%,3.40%and 12.50%,respectively;2)There was an excellent linear relationship between the output voltage of the soil moisture sensor that carried by the pipeline robot and the soil volumetric moisture content,where the coefficient of determination was 0.990;3)The pipeline robot presented a high accuracy of autonomous cruise positioning,with a mean relative error of 1.47%.The field experiment show that:1)The pipeline robot system was captured the plant root images with high-throughput in the field environment.Root growth dynamics was obtained to further extract the parameters of root length,area,average diameter and density from the images;2)The pipeline robot was accurately monitor the soil moisture in the root zone,where the mean relative error of the measured was 2.23%,compared with the drying measurement;3)Once the system was initially fully charged,the pipeline robot system operated independently for no less than 7 days,where the maximum cruise monitoring distance was about 48m.The pipeline robot system can be expected to realize insitu and high-throughput measurement of plant root and soil moisture in the root zone under field environment.The growth of root can be extracted after image recognition and segmentation.The finding can also provide the technical support to monitor the growth status of root in water-saving irrigation.