Simulation of vibration harvesting mechanism for sea buckthorn

Sea buckthorn (SBT) is an ideal plant for ecological management and thus planted widely in western China. Its fruit is of high nutritional and medicinal values. However, its economic value is far from development because of high cost for harvesting SBT fruits. Mechanical vibration is one of feasible way to make fruit separation. To design proper vibratory harvesters for tree crops, the vibration harvesting mechanism of SBT was simulated and analyzed by the finite element method. First, a three-dimensional solid model of SBT tree was built by Pro/E and imported into ANSYS. Next, modal analysis was performed to determine the natural vibration properties of SBT tree such as the natural frequency and vibration mode. Finally, harmonic response analysis was applied to determine the steady-state response when a sine load was added to the SBT tree. The modal analysis results indicated that the first twenty order natural frequencies of SBT tree varied from 6.6 Hz (the first order frequency) to 31.8 Hz (the twentieth order frequency). Results of harmonic response analysis showed that the application of vibration force to the side branches is effective than to the trunk, with a slight damage to the tree. Moreover, the vibration force applied to the side branches was 58-78 N with a frequencies range of from 20 to 30 Hz, which ensured that the majority of SBT fruits were harvested from the tree. The simulation analysis results obtained in this study could provide a basis for the design and development of SBT vibration harvesters.