Computational Model for the Dynamic Characterisation of a Trunk Shaker

Abstract

The development of trunk shaker machines over the years has been based on test-error methods in field. Mathematical or computational models have been studied with great simplifications. This paper presents a method for modelling the dynamic behaviour of a trunk shaker with a test bench. Two mass configurations were used on the test bench as well as two different vibration frequencies on the trunk shaker. Acceleration values were recorded at different points of the system. The binomial shaker-post was computationally modelled, and its dynamic response was analysed based on a modal and transient study with a series of proposed simplifications. The results of the simulations were compared with experimentally recorded acceleration values. In both cases, a linear response to mass and frequency variation was observed in the acceleration that the shaker performed. There was a high correlation in the effective accelerations (error < 4%) between experimental and computational studies measured in the trunk shaker. However, there were higher errors when the post was used in the test in the post structure points. The greatest uncertainty in the model may lie in the assumption of contact between the attachment pad and the post, but if this is not carried out, it makes convergence in the computational calculations very difficult. The method has proved its worth in determining the dynamic behaviour of these machines.

Configurable trunk shaker for the mechanical harvesting of different fruit branches

“…The unbalance of the rotor of the machines produces forces (Shrivastava and Mohanty, 2020) that are transmitted to the tree trunks, generating accelerations in the branches where the fruits are located to be detached. The operation of trunk shakers has been characterised with mathematical models for decades (Eshc & Ee, 1989; Lang, 2006) and computational models exist (Hoshyarmanesh et al, 2017; Sanchez-Cachinero et al, 2022). The vibratory force generated is directly related to the mass, eccentricity of the rotating mass and to the square of the angular velocity at which it rotates (Jablon et al, 2021).…”

Simultaneous Trunk and Canopy Shaking Improves Table Olive Harvester Efficiency versus Trunk Shaking Alone

“…Maximum fruit removal with a shaker is achieved when the shaking frequencies approach the tree's natural frequency. However, the proper shaking frequency varies for each individual tree, as the tree's natural frequency is a function of its size, age, morphology, wood properties, moisture content, and leaf density [11,12]. The tree's natural frequency can even shift during the harvest season due to mass changes during harvesting [13].…”

“…Olive trees significantly damp trunk vibrational energy due to their wood properties and branch orientation (Figure 2). the tree's natural frequency is a function of its size, age, morphology, wood properties moisture content, and leaf density [11,12]. The tree's natural frequency can even shift dur ing the harvest season due to mass changes during harvesting [13].…”