Fig.1 Arrangement of measuring points

Fig.2 Z-direction acceleration response curve of chestnut treeⅡB2 point under vibration of 26 Hz frequency

Fig.3 Dynamic model of vibration harvester-chestnut tree M1, The mass of eccentric motor (except eccentric block); M2, The equivalent mass of chestnut tree at the clamping point; m, The mass of eccentric block, kg; ω, The rotation frequency of eccentric block, r·s-1; r, The eccentricity of the eccentric block, m; k, The equivalent elastic coefficient, N·m-1; c, The equivalent damping coefficient, Ns·m-1; L, The distance between the rotating shaft of the excitation device and the center of chestnut tree, m.

Fig.4 Stress analysis of fruit induced by excitation P, The center of mass of fruit; f(t), The excitation force; N, The separation force between the fruit and the stalk; F, The inertia force; Fn, The normal inertia force; Ft, The tangential inertia force; G, The gravity of the fruit itself, N; φ, The angle between the fruit branch and the vertical direction; α, The angle between the normal inertia force and the vertical direction, °; ap, The fruit acceleration; an, The fruit normal acceleration; at, The fruit tangential acceleration, m·s-2.

Fig.5 Acceleration amplitude variation curves of three-direction acceleration at measuring point A1 and A3 on treeⅠ a,Sample tree Ⅰ point A1; b, Sample tree Ⅰ point A3.

Fig.6 Acceleration amplitude variation curves at measuring point A2 on tree Ⅰ and point A1 on tree Ⅲ a,Sample tree Ⅰ point A2; b, Sample tree Ⅲ point A1.

Fig.7 Physical picture of chestnut fruit 1, Empty chestnut bud; 2, Mature fruit; 3, Immature fruit.

Fig.8 Shaking down the chestnut fruit separated from the chestnut bud

Fig.9 Statistical figure of dropped fruit at different frequencies A, Sample tree Ⅰ; B, Sample tree Ⅱ; C, Sample tree Ⅲ.

Fig.10 Curve fitting of Chinese chestnut fruit dropping rate with frequency change a, Tree Ⅰ mature fruit; b, Tree Ⅰ immature ripe fruit; c, Tree Ⅱ mature fruit; d, Tree Ⅱ immature fruit; e, Tree Ⅲ mature fruit; f, Tree Ⅲ immature fruit.