Almost all fresh-market sweet cherry is currently hand-picked. A decreasing labor supply and rising harvesting costs have caused producers to begin moving toward mechanical harvesting. This study focused on studying different combinations of shaking frequency and duration for a hydraulically-powered mechanical shaking end-effector for effectively harvesting fresh-market sweet cherry from "Y" trellis trees. Shaking frequencies of 14 and 18 Hz, combined with shaking durations of 2 and 5 s, were evaluated in an orchard environment. Dislodged fruit was captured on a sheet laid under the tree, collected and weighed after each shaking interval. This procedure was repeated 4 or 10 times based on two different shaking durations used in the study to reach a cumulative shaking time of 20 s. Each combination was replicated on three trees. Results indicated that the first 2-s interval of 14 Hz shaking removed 29% of total fruit on average from the test trees, and the first 5-s interval of 18 Hz shaking removed 38% on average. Multiple shaking intervals with a total of 20 s shaking duration removed 81%, 73%, 62% and 59% of total fruit on average from four 5-s 18 Hz intervals, ten 2-s 14 Hz intervals, four 5-s 14 Hz intervals and ten 2-s 18 Hz intervals respectively, indicating that both frequency and duration have effects on fruit removal efficiency of a mechanical cherry harvesting system. Based on visual observation, over 60% of remaining fruit were growing on long and slender twigs. This result suggested that a proper pruning of cherry trees to minimize the number and/or length of small and long twigs could contribute substantially to the improvement of the overall fruit removal efficiency of the shaking-based mechanical harvesting system.
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