Modal properties of fruit-rachilla system of the macaw palm

Abstract

The macaw palm has been domesticated due to its potential use in the production of biofuel, in addition to several co-products that can be generated from its oil and pulp. One of the current challenges in this area is the harvesting, as there are no specific machines for this operation. Therefore, it is necessary to determine the appropriate information regarding the physical properties of the plant, so that it is feasible to develop the technologies necessary for the commercial scale application of macaw palm, allowing it to contribute to the sustainable production of raw material for the biofuel industry and other co-products. The principle of mechanical vibration can be used to shed fruit from trees when ripe, and it can be a method used for harvesting. Thus, as proposed in this study, it was necessary to study the dynamic behavior of the fruit-rachilla system during vibration. Hence, the modal properties of the system were determined. A study on the dynamic behaviors was carried out using a deterministic finite element model, and the natural frequencies were obtained through a frequency-scanning test to evaluate the model. The mean relative error (MRE) between the measured and simulated natural frequencies was also used to evaluate the model. The natural frequencies, determined experimentally, varied from 26.21 to 33.45 Hz on average, whereas the simulated frequencies varied from 24.81 to 39.27 Hz. The overall MRE was 9.08%. Once the model was validated, a sensibility test was carried out, which showed that the density of fruit and the elasticity modulus are the parameters that most influence the natural frequencies of the fruit-rachilla system.

Modeling and simulation of the dynamic behavior of the macaw palm fruit-rachilla system

“…Several models have been developed for the study of macaw palm, such as presented by Velloso et al 15 and Villar et al 19 However, the approaches were simple and did not allow these models to be able to recreate scenarios that match the reality. From high-fidelity models of the macaw palm fruit-rachilla system, the natural frequencies will be estimated more accurately.…”

“…This simplification has been employed in the simulation of several biological systems with similar geometric configuration. 19,20,22,[47][48][49] The combination of geometric parameters and mechanical properties is responsible for the quality the simulation and the improvements in the models used. Coelho et al, 21 when studying the fruit-branch-peduncle system of coffee, found that the model developed using simplifications of the actual physical system showed dependence on the mechanical parameters (elasticity modulus and specific mass).…”

“…11,12 Domestication, physical properties, and fruit harvesting systems have been studied to learn how to obtain quality raw material for macaw palm production. [13][14][15][16][17][18][19] The use of computational modeling through numerical simulations is a skillful way of designing, understanding, and evaluating harvesting mechanisms without the need for destructive testing and the design of prototypes. [20][21][22][23] It is believed that the principle of mechanical vibration is applicable to the harvest of macaw palm fruits, 18 so the determination and knowledge of modal properties, natural frequencies, and modal forms of the plants, or part of them, are necessary when computationally studying the behavior and the interaction of the plant with the machines that can promote the harvest of its fruits.…”