Development of a Variable-Rate Sprayer with Laser Scanning Sensor to Synchronize Spray Outputs to Tree Structures

Abstract

Efficient and effective precision spray equipment and strategies are in high demand to reduce pesticide use in tree crop production. An experimental variable-rate air-assisted sprayer implemented with a high-speed laser scanning sensor was developed to control the spray output of individual nozzles in real time. The sprayer consisted of a laser scanning sensor control system and an air and liquid delivery system. Each nozzle in the delivery system, coupled with a pulse width modulated (PWM) solenoid valve, achieved variable-rate delivery based on occurrence, height, and width of the target tree and its foliage density. Other components of the sensor control system included a unique algorithm for variable-rate control that instantaneously processed measurements of the canopy surfaces. To determine system delay time, a high-speed video camera was used to record the time period between sensor detection of the canopy and nozzle activation. Spray deposition uniformity inside canopies was verified by quantifying spray coverage inside four ornamental nursery trees of different sizes and canopy densities at 3.2 and 6.4 km h-1 travel speeds. Test results demonstrated that differences in spray coverage inside the canopies of these four trees in the spraying direction were not statistically significant, even though these trees had different structures, canopy volumes, and foliage densities. The canopy volume and foliage density measured with the algorithm developed for the laser sensor-controlled detection system exhibited little variation between the two travel speeds. Design criteria for the sensor-controlled system in the experimental sprayer were acceptable for variable-rate application, having great potential for spray volume and drift reduction, and thus reducing environmental impact.

A Method to Obtain Orange Crop Geometry Information Using a Mobile Terrestrial Laser Scanner and 3D Modeling

“…2017, 9,763tree row and as the vehicle moved along the alleys of the grove, the third dimension of the data was added (Figure 1b). To acquire data from the LiDAR sensor and the RTK-GNSS receiver synchronously, a piece of software was developed using Processing (Processing v2, 2014) [22].…”

“…By estimating the distance between its centre and the nearest obstacle in several directions (if a 2D or 3D sensor is used), a LiDAR sensor can be used to create 3D models of its surroundings. An advantage of terrestrial acquisition systems in the context of agricultural and horticultural applications is that the sensors can be attached to spreaders and spraying machines enabling variable-rate applications on a real-time basis [8,9], thereby not requiring an extra operation to acquire data from orchards or groves; these are often referred to as "mobile terrestrial laser scanners" (MTLS) [7,[10][11][12][13].…”

Evaluation of Object Surface Edge Profiles Detected with a 2-D Laser Scanning Sensor

“…The program was very similar to the program reported by Liu and Zhu [32]. The contours of the images for the detected objects were also constructed by the morphological operator and edge detection method [31,32]. …”

“…Ultimately, a laser scanning sensor is integrated to the variable-rate spray control system of an air-assisted sprayer [31]. Another 270° radial range laser sensor is verified in the detection of complex-shaped objects, and is successfully installed in an air-assisted sprayer [32,33].…”

Application of light detection and ranging and ultrasonic sensors to high-throughput phenotyping and precision horticulture: current status and challenges

“…The proposed set up of the laser sensor, facing the side of the tree vertically and moving along the grove alleys to measure transversal sections of the row, was similar to the ultrasonic systems proposed by McConnell et al 12 and by Giles et al 13–15 and was later used by most of the studies in the application of LiDAR to tree crops 23,24 . Unlike the ultrasonic sensors, the 2D LiDAR scanner can measure distances in several directions within a plane (Fig.…”