Determination of Detachment Frequencies of Ripe Coffee Fruits (Coffea Arabica Var. Colombia) by Means of a Numerical and Experimental Approach

Abstract

In this study, it is proposed an experimental and numerical approach to identify a bandwidth of harmonic frequencies where ripe fruits of Coffea arabica L. var. Colombia can be selectively stimulated. For this purpose, a geometric model was designed computationally to represent the topology of the coffee fruit-peduncle system in all ripening stages. Using analytical models and pseudo-experimental data, the mechanical properties were estimated to carry out a finite element analysis of the system. It was verified with a detachment model that fruits can be detached when a specific harmonic force (mechanical vibrations) is applied on the fruits in determined frequencies which correspond to the second vibration mode of the fruits. Results indicate that dynamic excitations between 130 to 150 Hz could detach only ripe fruits since fruits that were in other ripening stages were not stimulated until detachment in that bandwidth.