Experiment and analysis on walnut (Juglans regia L.) shedding force based on low-frequency vibration response

Abstract

Walnut (Juglans regia L.) is a highly valuable crop and is widely used as a food, medicine, and industrial product. Studying walnut detachment force is an important prerequisite for bed harvesting through low-frequency shaking. In this study, the stalk–branch and stalk–fruit kinetic models were analyzed under different vibration modes by establishing a local vibration model. A platform was built to conduct tests of static separation force separately for different modes. The inertial force and static separation force of the vibration response were analyzed by combining each vibration parameter with the local fruit–stalk–branch vibration model, and the separation ratios were derived under different vibration parameters. In the vibration response with a frequency of 10 Hz and amplitude of 80 mm, the maximum separation ratios of inertial tensions at connection points between the branch and stalk, stalk and tail fruit, and stalk and side fruit were 0, 25.5%, and 26.3%, respectively; the maximum separation ratios of the inertial bending moment were 86.4%, 96%, and 83%, respectively; and the detachment difficulty coefficient of the motion mode generating inertial bending moments was much lower than that of the mode generating inertial tensions. The relationship between the separation force and biological characteristics was analyzed, and field vibration tests were conducted to verify the separation force tests. The results of the study can guide development and adjustment of vibration parameters of a vibrating device for harvesting and help further study of the effect of excitation mode on fruit shedding.