The mechanization of field activities has been the response of coffee producers to the labor shortage, especially for fruit harvesting. The use of mechanical harvesters allows greater harvesting efficiency and ensures the economic viability of coffee plantations, which currently depend mainly on the reduction in production costs. The principle used for mechanized coffee harvesting is based on the principle of mechanical vibration. The objective of this study was to analyze the dynamic behavior of the coffee fruit-peduncle-branch system under mechanical vibration and the impact of the vibrating rods on the fruit detachment process in association with this behavior. Fragments of coffee branches containing fruits in the unripe and ripe stages were used in this experiment. These samples were subjected to different frequencies (20, 30, 40, and 50 Hz) and amplitudes (0.002, 0.003, and 0.004 m). Another variable analyzed was the form of vibration transmission to the fruits, with the vibrations being transmitted to the samples with or without the impact of the fiberglass rods. The fruit detachment efficiency increased as the ripening stage progressed from unripe to ripe. A higher detachment efficiency occurred with the increase in vibration frequency and amplitude because of the higher vibrational energy imposed on the fruit. The detachment efficiency was low when the vibration was transmitted without the impact of the rods. Conversely, the vibration in combination with impact achieved a mean detachment efficiency of approximately 90%

The development of efficient machines for coffee harvesting requires solid knowledge about the dynamic behavior of the plant. Vibration transmissibility is a parameter on dynamic behavior that may help understand this process. The aim of this study was to evaluate the average vibration transmissibility in coffee fruit-peduncle-branch samples containing unripe and ripe fruits. The experiments were performed using Arabica coffee plants of the cultivar Catuaí Vermelho. The samples were submitted to three vibration frequency levels, 20, 30 and 40 Hz, induced to the branch with impact of rigid fiberglass rods moving at a constant amplitude 2 mm. Data on acceleration were collected using an accelerometer fixed to the branch. The frequency of 20 Hz presented the highest transmissibility. Samples containing ripe fruits also presented high transmissibility when compared to those containing unripe fruits.