Shaking energy delivery on sweet cherry trees in different excitation modes

To evaluate energy consumption and delivery patterns on fruit tree of a newly designed limb shaker for sweet cherry harvest, a set of dynamic tests were conducted on Y-trellis sweet cherry trees in orchard environment under different excitation modes. The energy consumption of the shaker was calculated based on the input power of the hydraulic motor. To understand the energy delivery patterns, a group of accelerometers were fixed on tested trees to obtain response information under different excitation modes. Each branch was divided into three 'response zones' according to its locations. Maximum kinetic energy of each 'response zone' of branches was calculated to study the tree energy response. Filed tests were conducted at excitation frequencies of 6, 10, 14 and 18 Hz with three excitation modes of Clamp, Impact[1] (with 1.3 cm clearance between branch and shaker), and Impact[2] (with 2.5 cm clearance between branch and shaker), respectively. Meanwhile, three locations (Low, Middle and High) in the excitation branch were chosen as the excitation points in these tests. Test results indicated that the excitation branch could obtain majority of the delivered kinetic energy in high excitation frequency. The excitation of Clamp could deliver largest amount of maximum kinetic energy to the tested trees in most conditions, while the percentage of that delivered to the excitation branch was the lowest and energy consumption of the shaker was the highest. At the excitation frequency of 14 Hz, the tested tree could obtain the total maximum kinetic energy of 2.14, 2.07 and 1.50 J, with 84.27%, 93.55%, and 93.93% of energy delivered to the excitation branch, and energy consumption of the shaker was 0.83, 0.79 or 0.74 kW, in excitation modes of Clamp, Impact[1], and Impact[2] respectively. Test results also indicated that the tested trees could obtain the highest maximum kinetic energy at Low point excitation, while the percentage of that delivered to the excitation branch was lower than that at the Middle point excitation, and the energy consumption of the shaker was the highest.