Mechanism simulation analysis and prototype experiment of Lycium barbarum harvest by vibration mode.

Recently, as scientific research has been further explored, the health care functions of the Lycium barbarum (L. barbarum) in anti-oxidation, anti-aging, anti-fatigue, protecting liver, improving body immunity, eye protection and other aspects have been further confirmed. Its unique and nutrient-rich health function is recognized gradually in western countries, and the market demand of the L. barbarum is expanding each year. The L. barbarum blooms and bears fruit continuously during the growing season which begins in mid-May. Depending on the picking time around the year, the L. barbarum fruit can be divided into spring, summer and autumn fruit. In order to make dried L. barbarum keep good commodity characters, the L. barbarum is harvested at 80 percent maturity. The full bearing period of L. barbarum is from May to September every year, which is the picking peak of L. barbarum. It must be picked once about every 7 days. For centuries, the mechanized harvesting of L. barbarum has been a tough problem. Its harvesting has been artificial, which brings about low picking efficiency and high harvesting costs. With the continuous expansion of L. barbarum acreage, fruit picker has been increasingly scarce, which will be followed by rising picking costs. It's no doubt that the picking has become the bottleneck restricting the development of L. barbarum industry. Aiming at realizing the harvesting mechanization of L. barbarum and establishing the theoretical guidance and design basis for the L. barbarum picking machine, the vibration picking mechanism of L. barbarum plant's fruiting branches in picking was studied, the parameter optimization and simulation analysis was done to determine exciting force vector and rotational speed of driving wheel, and an experiment was conducted to prove the obtained rotational speed of driving wheel in this paper. First, we analyzed the working principle of the picking machine to get the vibration picking mechanism. The fruiting branches' model was simplified and the L. barbarum plant's fruiting branches' physical model and mathematical model were got, which were solved by equation solutions. We then obtained the forced vibration response of the fruiting branch and the forced vibration picking inertia force exerted on ripe and unripe fruits and flowers on each node. Second, 10 L. barbarum trees were selected as the test samples. We measured the binding force and mechanical parameters of the L. barbarum and fruiting branches, such as the number of ripe and unripe fruits and flowers, diameter, length, elastic modulus, damping ratio of fruiting branches, and node number. Based on the principle of successful picking which is the ripe can be picked and the other parts wouldn't be picked, the parameters were optimized, and the inertia force changes of the fruits and flowers with rotational speed were simulated with the MATLAB software. Simulation results showed the reasonable rotational speed was 2 868.84-2 871.21 r/min. Finally, rotational speeds of 7 levels which came from the interval and beyond the interval were selected in the experiment. Using a self-developed experimental L. barbarum picking machine, the test was conducted at planting base of L. barbarum of Ningxia Academy of Agriculture and Forestry Sciences, and the fruit distribution before and after picking was compared. Experiment result showed that reasonable rotational speed was 2 870 r/min, which is within the reasonable simulation interval of rotational speed. Under this rotational speed, picking efficiency of ripe L. barbarum was 815 grains per minute, the picking rate of ripe fruit was 86.70%, the picking rate of unripe fruit was 7.36%, and the picking rate of flower was 7.43%. The damage rate of fruit was 8.62%. The efficiency ratio of machine to worker was 5.43. Due to the actual picking environment, this result differs from simulation conclusion that the ripe is picked totally and none of the unripe and flowers is picked. The results can provide a reference for the development of L. barbarum vibration picking machines. [ABSTRACT FROM AUTHOR]