Desenvolvimento de uma derriçadora semimecanizada para a colheita seletiva do café

Abstract

In Brazil, geographical factors are of paramount importance for producing quality coffee. Crop and, especially, harvest management requires the use of portable machines to gain efficiency due to the impossibility of mechanization. This work seeks the development of equipment to validate a methodology that proposes selective semi-mechanized harvesting. To this end, we used commercial equipment with a few adaptations and an electronic set for frequency control. For the tests, we used coffee crops in the south of Minas Gerais, Brazil, and Colombia. We measured the strength of the fruit's detachment at different stages of ripeness and the minimum acceptable for a 90% interval of confidence, adopting a difference of 1.5 N to validate these crops for the possibility of selective harvesting. The final tests were conducted in a crop with a proportion of 54% green fruits to 46% cherry fruits. The results demonstrate that the harvesting is not effective for the amplitude of 9.4 mm, even at the highest frequency of 33Hz. For the amplitudes of 16.5 mm and 23.7 mm, the selectivity efficiency occurred in the frequencies 22.5 Hz, 25.57 Hz, and 27.93 Hz, becoming full in the 33.4 Hz frequency. The best result obtained was 10.31% of green fruits at the frequency of 27.45 Hz and 16.5 mm amplitude, followed by 10.81% frequency 22.5Hz and 16.5 mm amplitude. The set of replicates with the lowest standard deviation, that is, the most accurate, was with an average of 11.76% in amplitude 16.5 mm and frequency 22.5 Hz. The data prove the possibility of selective semi-mechanized harvesting with a percentage of green fruits below 20%, as proposed. The amplitude/frequency ratio is relevant for selective harvesting and its harvesting efficiency. The data shows that there is no ideal frequency. The important thing is to adjust the amplitude/frequency ratio. We have proved that the greater the amplitude, the lower the frequency of the beginning of the selection. However, the ideal transmission of kinematic energy approaches the frequency of 25 Hz, considering that the frequency is the main factor for harvesting efficiency.