Optimization of Vibration Parameters for Red Jujube Trees with Different Diameters

Abstract

Vibratory harvesting is the primary method used to harvest red jujubes. This study aimed to improve the efficiency of vibratory harvesting for red jujubes and identify the optimal parameters for harvesting at different jujube tree diameters. A model for the forced vibration dynamics of jujube trees was established, and a three-dimensional model was constructed for different diameter variations. A kinematic simulation analysis was then conducted to determine the inherent frequency and modal vibration patterns of jujube trees. Harmonic response analysis was performed to study the displacement and acceleration responses of jujube trees with different diameters to different vibration factors. Subsequently, vibration tests were carried out on the jujube trees. The results showed that the vibration characteristics of trees with different diameters were distinct at each vibration order, and the maximum number of vibrating branches differed at different orders of vibration. The vibration frequency ranges for vibration harvesting of jujube trees with 30 mm, 50 mm, and 70 mm diameters were determined as 4–30 Hz, 6–25 Hz, and 17–29 Hz, respectively. Furthermore, the study obtained the optimal vibration parameters for jujube trees by establishing the regression equations of harvest rate and each vibration factor. For jujube trees with a diameter of 30 mm, the optimal parameters included a vibration frequency of 30 Hz and a vibration amplitude of 15 mm. For jujube trees with a diameter of 50 mm, the optimal parameters included a vibration frequency of 18.55 Hz and a vibration amplitude of 12.52 mm. Lastly, for jujube trees with a diameter of 70 mm, the optimal parameters included a vibration frequency of 6 Hz and a vibration amplitude of 15 mm. This study provides a theoretical foundation and technical support for improving the efficiency of vibratory harvesting and identifying the optimal vibration harvesting parameters for jujube trees with different diameters.