Mechanism analysis and simulation of blueberry harvest by vibration mode

Abstract: Recently, the blueberry was served as the king of fruits, and people have been paying more attention to the health care effect, economic and medicinal value of the blueberry. Planting the blueberry is a new economic growth point in agriculture and forestry. The demand for blueberry exceeds the supply in the international market with high-speed growth demand. However, the blueberries are harvested depending entirely on hand picking in China with serious losses, and the picking cost accounts for 50%?70% of the total blueberry production cost. The old harvesting method restricts the widespread popularization and planting of blueberries. Research on blueberry picking machines and blueberry picking mechanisms is in its infancy in China. The price of blueberry picking machines is high. An experiment was conducted to change the artificial harvesting status of the blueberry, realize the mechanization of a high-bush blueberry-picking tool, and establish the theoretical guidance and design basis for the blueberry-picking machine for Chinese national conditions. We studied the vibration mechanism of the high-bush blueberry in picking and identified the picking frequency by simulation analysis and the experimental verification. First, we analyzed the working principle of the picking machine to get the vibration picking mechanism. The blueberry plants' geometry model was simplified and analyzed to get the blueberry plants physical model and the mathematical model, which was solved by a partial differential equation solution. We then obtained the forced vibration response of the blueberry plants and the forced vibration picking inertia force at steady state of the blueberry fruit. Second, ten strains of blueberry trees were selected as the test samples. We measured the binding force and mechanical parameters of the blueberry plants, such as the diameter, length, density, elastic modulus, fruit, and tree growth parameters. The vibration shape of the fruit branches and the inertia force of the fruit were simulated by using MATLAB software simulation, and the blueberry picking frequency at vibration condition was 14-16 rad/s. Finally, using an experimental self-developed blueberry picking machine at Xinkang blueberry planting area, in Wulongbei, Zhen'an District, Dandong City, Liaoning Province, the vibration shape of the fruit branches was observed and the fruit distribution before and after picking was compared. The results show that: there are fewer errors between the actual vibration response and the simulation results, but the overall vibration shape of blueberry branches, the vibration response, and picking effects are consistent with the simulation results. In addition, the effect of frequency on blueberry picking was analyzed by the experiment. The number of the mature fruit, ripe fruit, damaged fruit and the fruit left on the branch under different picking frequency were recorded. Then, the picking fruit rate, the fruit damage rate and the left fruit rate were calculated. The reasonable picking frequency is 15 rad/s, and the quality evaluation indexes at this frequency are as follows: the picking efficiency is 913 pieces/min, the picking ripe fruit rate is 2.99%, the damage fruit rate was 2.86%, the leaving rate is 3.17%, and the ratio of machine to worker is 10.14.