AgriEngineering, Vol. 7, Pages 364: Determination of the Modal Properties of the Coffee Plant (Coffea arabica L.): A Study Under Field Conditions

AgriEngineering doi: 10.3390/agriengineering7110364

Authors:
Mariana R. Pereira
Fábio L. Santos
Francisco Scinocca
Hector A. Tinoco
Geice P. Villibor

Through the principle of mechanical vibrations, coffee can be efficiently harvested. However, this process is affected by factors related to the machine and the plant. Thus, the modal properties need to be determined. The aim of this study is to characterize the dynamic behavior of coffee plants based on their modal properties under field conditions, with the fruit at different ripening stages. Fifteen randomly selected coffee plants (Coffea arabica L.), Catuaí Vermelho variety, were instrumented to collect field data and evaluate different scenarios. This study presented an innovative methodology, where coffee plants were evaluated under field conditions using experimental modal analysis at different positions along the plants and considering the immature and mature ripening stages. Based on experimental modal analysis tests, it was possible to observe that there was a higher incidence of natural frequency peaks clustered between 20 and 40 Hz. The values of the damping ratios of the plagiotropic branches of coffee plants with predominantly ripe fruits relative to the upper, middle and lower thirds were 0.145, 0.134 and 0.127, respectively. The results suggest that selectively harvesting coffee fruits solely through vibration application is not a viable option, exclusively by mechanical vibrations. This conclusion arises from the lack of significant differences observed in the pending loads of fruits at various ripening stages, coupled with the overlapping values of frequencies identified within the studied frequency bands. This work can be employed to improve existing equipment and the design of new machinery for coffee harvesting by mechanical vibrations.

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Mariana R. Pereira www.mdpi.com