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Highlights

The motion responses of fruits varied greatly in different excitation modes.

Abstract. To study the shedding frequency and motion response of Chinese Jun jujube fruits with different excitation modes, a vibration device with three excitation modes (horizontal, vertical, and rotational) was designed. The mature fruits were categorized according to their degree of dryness (fresh, half-dried, and dried). The basic physical parameters (volume, density, pedical-fruit retention force, etc.), shedding frequency, and motion response of the fruits were measured. With horizontal excitation, the response of the fruits was mainly pendulum motion, which increased as the excitation amplitude increased, while the shedding frequency of the fruits correspondingly decreased. However, with vertical excitation, the response of the fruits was mainly a compound motion comprising pendulum and beam-column motions. As the excitation amplitude increased from 5 to 10 mm, the shedding frequency of the fruits decreased dramatically, but further decrease in the shedding frequency was negligible as the excitation amplitude increased to 15 mm. With rotational excitation, the fruits exhibited centrifugal rotation in an approximately horizontal plane, and the amplitude and frequency necessary to achieve dynamic separation were small. It was concluded that the optimal excitation mode for Jun jujube is vertical excitation with an amplitude of 10 mm and frequency between 6 and 10 Hz.