The contribution of fruit and leaves to the dynamic response of secondary branches of orange trees

The current commercial technologies for mass harvesting fruit are based on the application of forced vibration to the tree, which is transmitted to the fruits causing their detachment. The dynamic behaviour of the plant under forced vibration is of special interest to improve the design and use of the machinery. The objective of this work is to determine the effect of fruit and leaves on the dynamic response of the citrus branch. In this study, 22 secondary branches of 'Valencia' sweet orange trees were tested by applying forced vibration and measuring the response of the branches with triaxial accelerometers. The branches were tested in three stages: in-fruit branch, out-of-fruit branch and out-ofleaf branch. Three natural frequency values were identified in the branches, and were established as 2, 7 and 11 Hz. Acceleration transmissibility along the branch decreased as vibration frequency increased. The acceleration transmission values were highest for the first natural frequency, and were up to 1.3-fold greater in the out-of-fruit branch and up to 4.6-fold greater in the out-of-leaf branch. The presence of fruits on the branch did not modify the branch natural frequency values but did slightly reduce the values of acceleration transmissibility. However, the presence of leaves on the branches had a double effect, reducing the first natural frequency and drastically damping acceleration transmissibility. (C) 2020 IAgrE. Published by Elsevier Ltd. All rights reserved.