靶向灭草机器人药液喷洒空气动力学模型建立与验证

为提高除草剂的有效利用率、降低环境污染,该文研制了一种靶向灭草机器人,建立机器人的药液喷洒动力学模型是提高对靶施药精度的关键。在综合考虑多种影响因素前提下,采用空气动力学原理建立了液滴在喷洒过程中的动力学模型,并推导出液滴的落地点公式;在此基础上通过计算机数值模拟得出了液滴群的落地覆盖区域,同时分析了液滴阻力特性及各工作参数对运动过程的影响;在室内无风条件下,应用高速摄像技术进行了喷洒试验,将液滴群的实际落地覆盖区域与理论覆盖区域比对,相对误差为8%~13%,同时采用吸水纸称质量法分析了药液有效覆盖区域的沉积量分布特性。研究结果表明:借由药液喷洒动力学模型得出的理论药液覆盖区域与试验结果具有一定的吻合性,验证了模型的适用性。该研究可为搭建相关靶向喷洒系统提供参考。

Aerodynamics modeling and validation on liquid medicine spraying of target weeding robot

Abstract: Field weeds have a great effect on the yield of normal economic crops. The commonly used methods of weeding include artificial weeding, mechanical weeding, weed quarantine, biological control, chemical control, and so on. Among those methods, chemical weeding is the best when it comes to sudden grass damage (the weeds of disaster break out suddenly), because it works well and takes less time. However, when we use chemical weeding, there are many problems such as low utilization rate of liquid medicine and serious pollution to the environment with overplus liquid. Therefore, toward-target pesticide application is proposed to solve these problems above all. As we all know, toward-target pesticide application machineries often use machine vision technology to obtain spatial location information of weeds, which makes the nozzle rigidly fixed on the machine and at the same time, the control system adjusts the valve to open and close to achieve the purpose of spraying. On this basis, we use spraying nozzle to change the direction of application, resulting in precision spraying in this paper. In order to study the law of motion for spray droplet, we established dynamic model based on application methods with the principle of aerodynamics, and then the formula of the droplet flying and the analytic formula of the falling point were deduced. Next, the numerical simulation analysis of the covering area was carried out. Especially, in the process of analysis, we discussed the resistance characteristics of spray droplets, the nozzle angle, nozzle speed, machine speed and injection pressure, which affect the movement process we discussed. What''s more, the model established above can also be used to control the location and shape of the droplet cover area by adjusting the working parameters, to improve the accuracy of toward-target pesticide application. Furthermore, in order to verify the correctness of the model, we set up the toward-target pesticide application platform and selected the special test site. Under no wind conditions, we conducted a simple target spraying test indoor, and then measured the geometric characteristics of actual liquid dripping place carefully. At the same time, the relevant parameters were obtained by high-speed camera technology. Next, we took the data into the dynamic model mentioned above to get the theoretical coverage of the liquid medicine, which was then compared with the actual coverage of the liquid medicine. Finally, it can be found that there is an error between the calculated and experimental results, and the error range is 8%-13%. In addition, to study the sedimentary characteristics of liquid medicine with this application method, we analysed the distribution law of the deposition amount of liquid medicine in the effective coverage area by water absorption paper weighing method. According to the analysis, it can be seen that the peak value of sediment changes regularly with the parameters such as the change of the nozzle angle, which suggests that the physical background of the model is clear, and the correlation between the parameters of the model and the sprinkler type is small, so the model transplant is strong. In other words, it can be used as a theoretical basis for the relevant spraying machinery.