Development of LIDAR-guided sprayer to synchronize spray outputs with canopy structures

Abstract

Variable-rate application is an effective way for nursery and orchard growers to reduce pesticide use and potential contaminations to the environment. To realize this goal, an intelligent air-assisted sprayer implementing a high speed laser scanning sensor (LIDAR) was developed to vary spray output of each individual nozzle to match target tree needs in real time. Each nozzle was coupled with a pulse width modulation (PWM) solenoid valve to achieve variable rates based on the occurrence and canopy characteristics of the target, such as height, width and foliage density as determined by LIDAR. A unique density algorithm was developed to calculate foliage density by mapping the surface roughness of the canopy during the spray application. A back pressure control unit was integrated into the system to minimize the pressure fluctuation due to frequent changes in nozzle flow rates. Delay time between the sensor detection of the canopy and the nozzle activation was determined with a high-speed video camera. Laboratory tests demonstrated that the design criteria of the experimental sprayer were acceptable for performing variable rate functions.