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Development of variable-rate sprayer with laser scanning sensor to synchronize spray outputs to tree structures

Chen, Y., Zhu, H., Ozkan, H. E.
Transactions of the ASABE 2012 v.55 no.3 pp. 773
air-assisted sprayers, algorithms, application rate, canopy, crop production, environmental impact, lasers, leaves, nozzles, ornamental trees, pesticide application, plant architecture, spray coverage, spray deposition, spray drift, spraying, video cameras
Efficient and effective precision spray equipment and strategies have been constantly demanded to reduce pesticide use in tree crop productions. 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 mainly 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 the occurrence, height, 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 the measurements of the canopy surfaces. To determine the system delay time, a high-speed video camera was used to record the time period between the sensor detection of the canopy and the nozzle activation. Spray deposition uniformity inside canopies were verified by quantifying spray coverage inside four ornamental nursery trees with different sizes and canopy densities at 3.2 and 6.4 km/h travel speeds. Test results demonstrated that the differences in spray coverage inside 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 had little variations with the two travel speeds. The design criteria for the sensor controlled system in the experimental sprayer were acceptable for variable-rate applications with a great potential in spray volume and drift reduction thus reducing environmental impact.