Abstract
Unmanned aerial vehicle (UAV) variable-rate spraying technology, as the development direction of aviation for plant protection in the future, has been developed rapidly in recent years. In the actual agricultural production, the severity of plant diseases and insect pests varies in different locations. In order to reduce the waste of pesticides, pesticides should be applied according to the severity of pests, insects and weeds. On the basis of explaining the plant diseases and insect pests map in the target area, a pulse width modulation variable spray system is designed. Moreover, the STMicroelectronics-32 (STM32) chip is invoked as the core of the control system. The system combines with sensor technology to get the prescription value through real-time interpretation of prescription diagram in operation. Then, a pulse square wave with variable duty cycles is generated to adjust the flow rate. A closed-loop Proportional-Integral-Derivative (PID) control algorithm is used to shorten the time of system reaching steady state. The results indicate that the deviation between volume and target traffic is stable, which is within 2.16%. When the duty cycle of the square wave is within the range of 40% to 100%, the flow range of the single nozzle varies from 0.16 L/min to 0.54 L/min. Variable spray operation under different spray requirements is achieved. The outdoor tests of variable spray system show that the variable spray system can adjust the flow rapidly according to the prescription value set in the prescription map. The proportion of actual droplet deposition and deposition density in the operation unit is consistent with the prescription value, which proves the effectiveness of the designed variable spray system.
Highlights
Pests and diseases of crops are a major factor affecting the yield and quality of crops, and chemical pesticides are the main means for their prevention and control
When the Unmanned aerial vehicle (UAV) was in flight operation, the variable spray system adjusted the rotational speed micro-diaphragm pump was drive by the Pulse width modulation (PWM) square wave signal
The results show that the variable spray system designed by square the research group ensures that the atomization effect is stable under the duty cycle of different PWM square wave signals, and the coefficient of variation of the system flow rate with the duty cycle of the PWM
Summary
Pests and diseases of crops are a major factor affecting the yield and quality of crops, and chemical pesticides are the main means for their prevention and control. Perez-Ruiz et al [8] used a geospatial prescription map prepared for olive trees, along with Real-Time Kinematic-Global Positioning System (RTK-GPS)-based position information to control the spray rate. This system only implements variable spray based on tree shape, and does not combine the degree of disease and pest with tree shape. A plant protection UAV variable spray system is designed based on the interpretation of the work prescription map. The system obtains prescription information for real-time location through graphic interpretation of plant protection UAV, and PWM-Proportional–Integral–Derivative (PID) control is used to adjust the spray volume quickly and accurately. The paper is organized as follows: Section 2 introduces the working principle of the plant protection UAV variable spray system based on prescription diagram interpretation.
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