Design and test of the fruit collecting device of camellia oleifera with angular scissor mechanism

Forest fruit collecting machinery is very necessary to balance the bulky machine size, the limited applicable environment, and the high spacing requirement in practical operation. The unsolved deflections have also started to hinder the full mechanization of the forest fruit industry. The angular scissor mechanism can be expected to improve the folding/deploying performance and environment adaptability of a mechanical automation system in the field of forest fruit harvesting. In this study, a new type of forest fruit-collecting device was proposed with a series of angular scissor elements in the variant arrangement. Firstly, the comprehensive description of the device was defined by the Cartesian and polar coordinate systems. All intermediate hinge points were not set along the same straight line. Among them, the intermediate hinge points of the horizontal circular scissor mechanism were located on the same arc. The intermediate hinge points of the side scissor mechanism were connected in a Z-shaped arrangement, leading to an angle of declination from the Z-axis in the global coordinate system. Both circular and side scissor elements were deployed with the angular scissor elements. Then, the kinematics analysis was also conducted for the forest fruit collecting mechanism, according to the sines and cosines. The theoretical expression was derived subsequently for the movement trajectories of hinge points on the collecting device. Moreover, the mathematical formula was deduced for the complete deployment angle of the side scissor mechanism, according to the sines. Next, an application example was taken as the camellia oleifera tree, a unique and well-known woody oil tree in China. The dimensional parameters of the camellia fruit collecting device were calculated to measure the canopy size of camellia oleifera trees, and the static friction coefficient between camellia oleifera fruits and collecting fabric. The average value of the static friction coefficient was obtained using friction angle testing with five groups of camellia oleifera fruit samples. The obtained structural parameters were selected to calculate the theoretical motion trajectories of several hinge points for the fruit-collecting device in MATLAB software. Furthermore, a simulation model of the forest fruit-collecting mechanism was established to verify the angular scissor elements using ADAMS software. The simulated position coordinates of each key hinge point were selected to compare the complete deployment angle from the theoretical analysis. The relatively low position errors of hinge points demonstrated the feasibility and accuracy of the theoretical design for the forest fruit-collecting device with the angular scissor. Finally, the physical prototype of the angular scissor fruit-collecting device was manufactured at the scale of 1:3 and then assembled. Collecting fabric was also covered over the angular scissor mechanism. The stored/deployed movement of the forest fruit collecting device was implemented at the site via the simultaneous control of the actuation displacement using two electric cylinders. Consequently, the complete deployment angle of the side scissor mechanism was measured to be about 25.67º, which was in better agreement with the previous theoretical parameter. More importantly, the ratio of the volume in the completely deployed state to that in the stored state for the forest fruit collecting device was estimated to be about 59.7, indicating the practical benefit of realizing collecting work of camellia oleifera fruits with the high stored/deployed ratio.