Development of a Laser-Guided, Embedded-Computer-Controlled, Air-Assisted Precision Sprayer

Abstract

Abstract. An embedded computer-controlled, laser-guided, air-assisted, variable-rate precision sprayer was developed to automatically adjust spray outputs on both sides of the sprayer to match the presence, size, shape, and foliage density of tree crops in real time. The sprayer was the integration of an embedded computer, a touch screen, a 270° radial-range laser sensor, a travel speed sensor, a unique algorithm, a custom-designed automatic flow rate control unit, and 40 pulse-width-modulated (PWM) nozzles. The accuracy of the sprayer to detect different-sized trees and control the spray outputs of individual nozzles based on tree structures was tested in a commercial nursery. Spray deposition qualities between variable-rate and constant-rate operational modes of the sprayer were also compared. Test results demonstrated the capability of the sprayer to measure different trees accurately and then control the spray outputs of nozzles independently to match tree structure. The outline profile similarity of paired images taken with a digital camera and with the laser sensor for three trees ranged from 0.81 to 0.89. To spray trees of different sizes and shapes, the sprayer in variable-rate mode (VRM) consumed 12.1% to 43.3% of the spray volume that was used in constant-rate mode (CRM) with an application rate of 468 L ha-1. Moreover, the sprayer had 30% and 55% greater coverage areas per amount of spray deposits in VRM than in CRM. This innovative sprayer should have significant potential to reduce pesticide waste, provide sustainable crop protection to growers, and safeguard the environment. Keywords: Automation, Nursery, Orchard, Precision agriculture, Variable-rate sprayer.