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Article

Vibrations Analysis of the Fruit-Pedicel System of Coffea arabica var. Castillo Using Time–Frequency and Wavelets Techniques

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Experimental and Computational Mechanics Laboratory, Universidad Autónoma de Manizales, Antigua Estación del Ferrocarril, Manizales 170001, Colombia
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Institute of Physics of Materials, Czech Academy of Sciences, Žižkova 22, 616 00 Brno, Czech Republic
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Central European Institute of Technology, Brno University of Technology, Purkyňova 656/123, 612 00 Brno, Czech Republic
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Department of Automatics (DAT), Federal University of Lavras (UFLA), P.O. Box 3037, Lavras 37200-000, MG, Brazil
*
Author to whom correspondence should be addressed.
Academic Editors: Wojciech Kolanowski and Anna Gramza-Michałowska
Appl. Sci. 2021, 11(19), 9346; https://doi.org/10.3390/app11199346
Received: 1 August 2021 / Revised: 17 September 2021 / Accepted: 23 September 2021 / Published: 8 October 2021
(This article belongs to the Topic Applied Sciences in Functional Foods)
Colombian coffee production is well-known, and selective manual harvesting plays a vital task in guaranteeing high ripe coffee fruit rates in this process, leading to its known worldwide aroma and flavor. To maintain this quality approach, selective harvesting methods based on mechanical vibrations are a promising alternative for developing technologies that could accomplish the challenging Colombian coffee production context. In this study, a vibrations analysis in coffee fruits at three ripening stages was carried out to evaluate the dynamic behavior at two frequency windows: 10 to 100 Hz and 100 to 1000 Hz. Two groups of fruits previously classified in the CIELab color space were chosen for the vibration test study samples. Time and frequency signals were characterized via FFT (fast Fourier transform), and bump wavelets were determined to obtain the frequency–time magnitude scalograms. The measurements were obtained in three degrees of freedom over the fruits: one for measuring the input force (computed in voltage way) and the other two measured by the velocity. The results revealed frequency ranges with specific resonant peaks between 24 and 45 Hz, and close to 700 Hz, where the ripe fruits presented higher magnitudes in the calculated parameters. FFT of the velocity and scaled mechanical impedance were used to estimate these frequency ranges. This work is an important step to identify a “vibrational fingerprint” of each Coffea arabica var. Castillo fruit-ripening stage. However, we consider that more experiments should be performed to reconstruct the modal shape in each resonance. In future studies, fatigue analysis could show which are the most effective frequency ranges to detach the ripe fruits from the perspective of a real selective coffee-harvesting scenario. View Full-Text
Keywords: vibration analysis; coffee; Coffea arabica; wavelet; time–frequency analysis vibration analysis; coffee; Coffea arabica; wavelet; time–frequency analysis
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MDPI and ACS Style

Cardona, C.I.; Tinoco, H.A.; Perdomo-Hurtado, L.; López-Guzmán, J.; Pereira, D.A. Vibrations Analysis of the Fruit-Pedicel System of Coffea arabica var. Castillo Using Time–Frequency and Wavelets Techniques. Appl. Sci. 2021, 11, 9346. https://doi.org/10.3390/app11199346

AMA Style

Cardona CI, Tinoco HA, Perdomo-Hurtado L, López-Guzmán J, Pereira DA. Vibrations Analysis of the Fruit-Pedicel System of Coffea arabica var. Castillo Using Time–Frequency and Wavelets Techniques. Applied Sciences. 2021; 11(19):9346. https://doi.org/10.3390/app11199346

Chicago/Turabian Style

Cardona, Carlos I., Hector A. Tinoco, Luis Perdomo-Hurtado, Juliana López-Guzmán, and Daniel A. Pereira. 2021. "Vibrations Analysis of the Fruit-Pedicel System of Coffea arabica var. Castillo Using Time–Frequency and Wavelets Techniques" Applied Sciences 11, no. 19: 9346. https://doi.org/10.3390/app11199346

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