Design and experiment of vibratory harvesting mechanism for Chinese hickory nuts based on orthogonal eccentric masses

Beating is the usual way to harvest Chinese hickory (Carya cathayensis Sarg.) nuts because of large size of trees and scattered distribution of nuts. To ensure the effective transmission of vibration energy and improve the efficiency of vibratory harvest, different modes of excitation force generated by different combinations of eccentric mass were analyzed. Firstly, the finite element model of a dwarf Chinese hickory tree was established. Harmonic response analysis was applied to determine the steady-state response when a sinusoidal load was exerted to the dwarf Chinese hickory tree model, and the maximum acceleration response can be obtained under the excitation frequency of about 22 Hz. Next, the flexible model of the dwarf Chinese hickory tree was imported into ADAMS through the data exchange function. The corresponding load was imposed on the tree model in ADAMS to simulate the response of the dwarf Chinese hickory tree to the excitations of different combinations of eccentric mass. The results show that when the treetop of one branch was excited, only the response of this excited branch was strong but those of other branches were low. When the trunk bifurcation was excited, all branches had high and similar response value. While the trunk was excited, all responses were low. Three-dimensional force generated by the combination of orthogonal eccentric masses was exerted to the tree. All the acceleration responses of the branches had the lowest standard deviation and coefficient of variation for different excitation points. Therefore the orthogonal eccentric masses have the potential to make the tree branches vibrate effectively and evenly in the process of vibratory harvesting, which may improve the harvesting efficiency.