Airblast sprayer electrification for real-time, continuous fan-airflow adjustment according to canopy density during pesticide application in 3D crops.

The parameters of the sprayer fan air stream, namely airflow rate and velocity, are crucial factors influencing the quality of the spray application and the amount of off-target spray losses when using an airblast sprayer in 3D crops. An integrated system enabling to vary the fan revolution speed continuously according to the canopy density was developed and mounted on a prototype vineyard airblast sprayer. The system consists of two ultrasonic sensors, able to determine the canopy density, whose output commands an electrically driven axial-fan through a Raspberry Pi based controller. The density values are received by the controller and then processed through an algorithm. The algorithm, used to define the fan setting, is based on the total air volume to be applied per ground area (m3 ha-1), a demonstrated key parameter for maximizing canopy deposition. The set fan revolution speed is then communicated by the controller to the electrically driven fan inverter. The results
confirm that the ultrasonic sensors are reliable for canopy density measurements. The field validation of the system demonstrates that the sprayer prototype providing a variable airflow rate can substantially increase canopy deposition and decrease spray drift compared to the commercial version of the same sprayer equipped with a conventional mechanical axial fan.