Vibration Response of Walnuts under Vibration Harvesting

Abstract

Vibration harvesting is a promising method for walnut production owing to its low cost and high efficiency. However, current research focuses on simulation analysis and lacks a theoretical model explaining the walnuts’ specific vibration response. This affects the design of the input vibration parameters during harvesting and thus reduces the harvesting efficiency. In this paper, a novel theoretical model of walnuts during vibration harvesting was established to analyze the vibration response, including the motion morphology (motion trajectory and dropping position) and detachment force. A field test was then carried out to verify the theoretical model. The theoretical and experimental results showed that the motion trajectory of the walnuts during vibration harvesting is similar to an ellipse, and the dropping position is at either of the two end points of the trajectory. The detachment force was found to be proportional to the vibration amplitude and the square of the vibration frequency theoretically. This paper provides a theoretical reference for designing the optimal input vibration parameters of a harvesting device to improve the harvesting rate of walnuts.

Optimization of Vibration Parameters for Red Jujube Trees with Different Diameters

“…In related studies, Fu et al [22], Yang et al [25], Zhuo et al [26] and Li et al [27] conducted earlier research on the vibration mechanisms of jujube trees and their branches, which provided a valuable theoretical foundation for the vibration harvesting of jujube trees. Fu et al [22] carried out experiments involving constant-frequency vibrations on samples of jujube tree branches, utilizing different amplitudes (3 mm, 5 mm, and 7 mm) and frequencies (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). The test results revealed a correlation between vibration frequency and instantaneous acceleration, while the effect of amplitude on instantaneous acceleration was found to be insignificant.…”

“…The structural response of the olive tree was also analyzed in relation to the type, position, and excitation frequency of the shaker. Liu et al [17] developed a theoretical model of walnut vibration during harvesting, analyzed vibration response in terms of motion morphology and separation force, and verified the model through field tests. Theoretical and experimental results showed that the response amplitude and frequency of walnuts are proportional to the vibration amplitude and frequency of the equipment, respectively, while the separation force is proportional to the square of both parameters.…”

“…Fu et al [22] simplified the jujube "branch-stalk-fruit" system as a double pendulum vibration model to analyze natural frequencies and obtain the natural vibration frequencies of the system (14.69 Hz and 17.26 Hz). Constant-frequency vibration tests were conducted on jujube tree samples at various amplitudes (3 mm, 5 mm, and 7 mm) and frequencies (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) to investigate the effects of vibration frequency and amplitude on the instantaneous acceleration of each branch. DHDAS analysis showed a correlation between vibration frequency and instantaneous acceleration, while amplitude did not have a significant effect.…”