Development and experiment of automatic target spray control system used in orchard sprayer

Abstract: In order to improve the utilization rate of pesticides and reduce the pesticide pollution to the environment, the control system of the automatic target spray was designed to focus on a Chinese low level of mechanization about the orchard sprayer and the invalid spray existed in the gap of fruit trees when the orchard sprayer sprayed with a continuous spray method. Whether the automatic target spray system sprayed to the fruit trees, depended on the detection distance between the orchard sprayer and the fruit trees by the application of distance measuring sensors and control program, which was installed on the GY8 caterpillar self-propelled orchard sprayer manufactured by Nantong Guangyi Mechanical & Electrical Co, Ltd. This paper compared the properties of three kinds of sensors which were MB7060 ultrasonic sensor, GP2Y0A710K0F infrared sensor and DT35-B15251 laser sensor, and tested the discernible spacing for the ultrasonic sensor and the laser sensor. The laser sensor was chosen as a detection device of the orchard sprayer for its high stability, fast response and good direction, while the other two sensors were abandoned for the following reasons that the infrared sensor was seriously affected by the sunshine, and the discernible spacing of ultrasonic sensor was too wide to satisfy the working conditions of the orchard sprayer. The parameters of the target range for spray trees could be adjusted in the system of the automatic target spray, based on different planted size (spacing in the rows and spacing between rows) of an orchard and the different travel speed of the orchard sprayer. The automatic target spray system could distinguish whether the fruit tree, or the gap between fruit trees and the gap in the canopies, so as to effectively control pests with the minimum dose of pesticide and the least environmental pollution. To ensure that the droplet could cover the whole canopy, the orchard sprayer must start to spray before the nozzle assembly reached the fruit trees and stopped spraying after the nozzle assembly leaves the fruit trees, so the laser sensor was installed in front of nozzle assembly 220 mm and delayed a period of time on the basis of the travel speed to stop spraying after the nozzle assembly left the fruit trees by calculation. The experiment of the discernible spacing of the automatic target spray system and field experiment was tested in the Jiamu forest farm in Aksu of Xinjiang. The results showed that the value of the minimum discernible spacing was lower at higher travel speed to lower travel speed. The discernible spacing of the automatic target spray system was 100-150 mm under the travel speed 0.5 m/s and 200-250 mm under the travel speed was 1.0 m/s. The saving rate of pesticides increased with the increase of the gap rate. Compared with continuous spray, the automatic target spray could save pesticides 27.9%, 53.7%, 76.9 % at the travel speed of 0.5 m/s and 27.3%, 54.5%, 81.0% at the travel speed 1.0m/s, respectively for the gap rate 20.0%, 35.2%, 52.9%. The saving rate of pesticides was higher than the gap rate of the fruit trees, because the pressure of the spray unit was low as the pesticide valve on initially. It is a favorable condition to save pesticide corresponding to thin canopy. Thus, the automatic target spray system of the orchard sprayer could effectively improve the utilization rate of pesticides.