Precision Variable-rate Control System for Mini-UAV-based Pesticide Application

Abstract

Mechanized and efficient pesticide application is an effective measure to prevent crop diseases, control pests, and ensure stable yield. For crops in greenhouses, due to the complex operating environment, the traditional mechanical spraying method will lead to excessive pesticide spraying and pesticide residues. Based on the ultrasonic sensor array, a small crop canopy volume calculation model is proposed, and the Pulse Width Modulation (PWM) control model of nozzle flow is established. The compensation time of opening and closing delay of the nozzle was determined to be 0.201 s by the high-speed photography method. The optimal operating speed was determined to be 0.3 m·s−1 through the benchmark test. Then, the precision variable spraying control method was integrated to develop the precision variable plant protection UAV based on an ultrasonic sensor array. The test results showed that the droplet deposition density was greater than 20 drop s·cm−2, and the droplet coverage rate of precision variable spraying was less than 30%. In the experimental area, the pesticide dosage of conventional and precision variable spraying was 0.24 L and 0.15 L, respectively, The precision variable-rate spraying saved pesticide usage by 34.5%. The system can realize precise variable spraying according to crop location and crop canopy volume changes. This study will promote the rapid development and application of precision spraying technology for small plant protection UAVs.