Simulation study on the effects of tine-shaking frequency and penetrating depth on fruit detachment for citrus canopy-shaker harvesting

The overall low detachment percentage in citrus mechanical harvesting is a concerning problem. Studies of the effects of tine-shaking frequency and penetrating depth on fruit detachment for citrus canopy-shaker harvesting have not been reported to date. The objective of this study was to examine how tine-shaking frequency and penetrating depth affect fruit detachment based on simulation and pertinent field experiments for a citrus canopy shaker that inserts a row of shaking tines into the tree canopy. According to evaluation of the branch/stem elasticity, density, and fruit detachment force, a cantilevered limb model, including a periodic shaking force, was constructed to simulate the shaking process in citrus canopy shaking. Simulation results demonstrated a positive correlation between the shaking frequency and maximum stress at the fruit end of the stem, and a 5 Hz shaking frequency found to be sufficient for fruit removal. It was also observed that the penetrating depth ensured that, when shaking spot was close to the junction of the limb and stem, the maximum stress increased at the fruit end of the stem. Field trial results agreed with the simulation results, with both simulation and experiments indicating highly significant effects (p < 0.01) from both the tine-shaking frequency and penetrating depth on fruit removal. The simulation method used here can be utilized for improvements in canopy-shaker applications.