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Field evaluation of turn compensation feature of pulse width modulation (PWM) – equipped agricultural sprayer

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2021 ASABE Annual International Virtual Meeting  2101190.(doi:10.13031/aim.202101190)
Authors:   Jonathan V. Fabula, Ajay Sharda
Keywords:   Agricultural sprayer, application error, pulse width modulation, sprayer speed, turn compensation.

Abstract. The turn compensation technology has the potential to reduce errors caused by the speed difference between the inner and outer boom section of the sprayers when applying in curvilinear passes. However, little research has been conducted to evaluate the extent of field area typically operated on curvilinear passes and technology's performance when applying the product at different turning radius. Field tests were conducted in three different fields using a 36.6-m sprayer with turn compensation technology. GPS coordinates and heading were used to calculate the turning radius of the sprayer. The turning radius was classified as extreme turn (<20.0 m), medium turn (20.0 m to 50.0 m), and slight turn (50.0 m to 100.0 m). Straight passes were classified when the turning radius exceeded 100.0 m. The results show that turning occurred near the grassed waterways, boundaries, and headlands. The product was applied during turning in 19.0% of field 1, 17.8% of field 2, and 22.5% of field 3. These could have been the percentage of field areas that may receive incorrect product rates if the sprayer does not have turn compensation. The speed difference between the inner and outer boom increases as the turn radius decreases. This could translate to an under-application and over-application on the outer and inner boom section, respectively. The application errors from such speed differential could vary from -48.2% to +1058.0 %. However, the PWM system implemented duty cycles based on turning speeds, resulting in more uniform product application across the field regardless of travel path.

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