| Lycium barbarum,as a common Chinese herbal medicine,has a variety of functions such as health-care and medical benefit which has been widely used in the field of health-care products,food production,medicine and so on.With the expansion of planting area,harvesting has become a bottleneck problem that restricts the sustainable and healthy development of wolfberry industry.Manual harvesting,which has the disadvantages of low efficiency and high labor intensity,is the main method for Lycium barbarum harvesting.The disadvantages of manual harvesting induce the pretty high production cost of Lycium barbarum.Thus,mechanization of harvesting is necessary to reduce the dependence on manual labor and improve the efficiency and quality for Lycium barbarum harvesting.Vibration harvesting devices is one of the most mature one among all kinds of Lycium barbarum harvesting devices at the present stage.However,there are still some problems to be solved in the vibration harvesting of Lycium barbarum,such as low harvesting ratio and high fruit damage rate.In this study,we take the Ningqi No.7 wolfberry as the research object.The numerical simulations and experiments were performed to study the vibration harvesting of Lycium barbarum.This study could help to improve the harvesting ratio and reduce the fruit damage in the process of Lycium barbarum harvesting.The main contents and results of this study are listed as follows:(1)Research on the dynamic characteristic of vibration detachment for Lycium barbarum fruit.The FEM model of branch-stem-fruit system was established.Numerical modal analysis was carried out to study the movement forms of branch-stem-fruit system in the process of vibration harvesting.The movement forms mainly include reciprocating swing,up and down swing,rotation movement and compound movement.The dynamic explicit analysis was performed to investigate the forced vibration characteristic of branch-stem-fruit system.The effects of excitation amplitude,excitation frequency and excitation form on the detachment force of Lycium barbarum fruit were studied.The optimal excitation parameters were also determined by comparing with the experiment results.It can be concluded that the optimal excitation amplitude and frequency should be 20 mm and 7 Hz,respectively.(2)Research on the vibration transmission characteristic of branches.The curved shape of fruiting branches caused by the natural growth and fruit ripening was simulated by applying sequential loadings on the different nodes of fruiting branch.The fitted curve of bended branch was then obtained.The effects of excitation position and damping ratio on the vibration transmission characteristics of fruiting branches were investigated with the transient dynamics analysis.The results indicated that the reasonable excitation position should be within the range of 100 mm around the Lycium barbarum fruit aimed to be picked.(3)Research on the falling bruise of mature Lycium barbarum fruit.The quasi-static compression simulation and corresponding experiment were performed to determine the mechanical properties of mature Lycium barbarum fruit.The FEM explicit dynamics analysis was applied to simulate the falling bruise of mature Lycium barbarum under different conditions.The relationships between the falling height,material of supporting board,falling angle and volume ratio of falling bruise were then analyzed.A mathematical regression model was established to evaluate the falling bruise of mature Lycium barbarum fruit by using response surface analysis.It can be concluded that the falling height has the most significant influence on the falling bruise of mature Lycium barbarum fruit.The effect of material of supporting board on the falling bruise is weaker than the falling height.The falling angle has the little effect on the falling bruise.In this study,the optimal excitation parameters of vibration harvesting and mathematical regession model of falling bruise were obtained numerically and experimentally for the Lycium barbarum.The results of this study provide the reference and theoretical basis on the design of vibration harvesting device for Lycium barbarum. |
