基于果树冠层识别的植保无人机可变角度变量喷施装置设计与试验

Design and Experiment of Variable Angle and Variable Spraying Device for Plant Protection Unmanned Aerial Vehicle Based on Fruit Tree Canopy Recognition

摘要:

针对当前无人机喷药喷施不均匀、雾滴飘移、肥药有效利用率低和浪费污染严重等问题，设计了一种基于果树冠层识别的植保无人机可变角度变量喷施装置。该装置通过摄像头采集果树冠层图像并传输至Jetson Orin Nano，利用ROI选取与子区间线扫方法实现冠层边界与果树行宽度识别，识别结果传至STM32控制器，其中冠层边界信息用于调节喷头角度，像素占比信息用于调控喷头流量，流量计与磁编码器反馈信号经模糊PID算法处理，实现喷头角度与喷施量双闭环控制。经试验验证，果树冠层边界算法离线识别率为91.58%。台架试验结果表明，该方法在果树行宽度识别中平均误差为7.32%，线性拟合R2=0.91；在喷雾验证中，当喷施角度大于靶区时，调节后可使靶区外沉积数量平均降低26.61个/cm2，雾滴沉积数量降低51.94%。当喷施角度小于靶区时，调节后可使靶区内外部雾滴沉积数量平均提升25.37个/cm2，雾滴沉积数量提高54.8%。核密度估计曲线更平滑，有效改善沉积分布均匀性。田间试验结果显示：统计检验结果为t=3.29、P=0.03，达到P<0.05的统计显著水平，装置开启状态下沉积效果更优，该方法实现了基于果树行宽度可变角度变量喷施控制，可有效提高雾滴利用率，为无人机果园精准施药提供技术支持。

Abstract:

In view of the current problems such as uneven spraying, droplet drift, low effective utilization rate of fertilizers and pesticides, and serious waste and pollution caused by traditional spraying methods of unmanned aerial vehicles (UAVs), a variable angle and variable spraying device for plant protection UAVs was designed based on fruit tree canopy recognition. This device collected the canopy images of fruit trees through the camera and transmited them to Jetson Orin Nano. The recognition of the canopy boundary and the row width of fruit trees was achieved by using ROI selection and sub-interval line scanning methods. The recognition results were transmitted to the STM32 controller. Among them, the canopy boundary information was used to adjust the nozzle angle, and the pixel ratio information was used to regulate the nozzle flow rate. The feedback signals of the flowmeter and the magnetic encoder were processed by the fuzzy PID algorithm to achieve double closed-loop control of the nozzle angle and the spray volume. It was verified that the offline recognition rate of the fruit tree canopy boundary algorithm was 91.58%. The bench test results showed that the average error rate of this method in the recognition of the width of fruit tree rows was 7.32%, and the linear fitting R2=0.91. In the spray verification, when the spray angle was greater than the target area, after adjustment, the average number of deposits outside the target area could be reduced by 26.61 per cm2, and the number of droplet deposits could be reduced by 51.94%. When the spraying angle was smaller than the target area, after adjustment, the average number of external droplets deposited in the target area can be increased by 25.37 per cm2, and the number of droplets deposited can be increased by 54.8%. The kernel density estimation curve was smoother, effectively improving the uniformity of sedimentary distribution. The field test results showed that the statistical test results were t=3.29 and P=0.03,reaching a statistically significant level of P<0.05. The deposition effect was better when the device was turned on. This method realized variable angle and variable spraying control based on the width of fruit tree rows, which can effectively improve the utilization rate of droplets and provide technical support for precise pesticide application in unmanned aerial vehicle orchards.