| In recent years,the rapid growth of China's wine industry is promoting the increase of vineyards.However,the wine grapes are harvested entirely depending on hand picking in China with high cost.Research on picking machine and picking mechanism of wine grapes is in its infancy in China.This paper studied the grape threshing process in order to optimize the structure of the picking machine,improve the threshing rate and decrease breakage rate.Based on the analysis of the dynamics characteristics of grape,a finite element model was established,which was used to provide reference for the design and analysis of threshing device.The structural parameters and working parameters of the threshing unit were studied by the bench test.Through the high-speed photography and comparation experiments of the threshing mechanism,the optimal scheme of flexible stripping is obtained.The main conclusions of this paper are as follows:1.The dynamic parameters of the grape fruit,such as static friction coefficient,friction coefficient and restitution coefficient,grape fresh viscoelastic parameters,fracture characteristics between grape fruit and fruit stalk,were tested,and provided the basic physical parameters for the establishment of grape finite model model.2.Based on ABAQUS,the viscoelastic collision model of the grape was established.Through the comparation between the simulation test and the actual test,it was shown that the reliability of the simulation model is quite good.The FBM(Fibers Bushing Model)fracture model between the grape fruit and the fruit stalk was established,and the simulated fracture test was in good agreement with the actual fracture test.Based on Python,the grape string model was developed.Python was useful to increase the speed of modeling.3.Firstly,a harvesting test bench was designed.The rotational speed,the bending stiffness and the distance between rotary shafts were taken as the orthogonal test factors.The rotational speed of combing roller selected three levels,including 120,160 and 200 r/min.The bending stiffness selected three levels,including 0.029,0.067 and 0.09 N m2.The distance between rotary shafts selected three levels,including 280,300 and 320 mm.The threshing time and the broken rate were selected as indices in the orthogonal test.The flexible pole tooth's bending stiffness was the only significant factor for the indices of breakage and threshing time.In addition,the effect of the bending stiffness on wine grape picking was analyzed by the experiment.When the rotational speed of combing roller was 160 r/min,the bending stiffness of flexible pole tooth was 0.067 N·m2 and the distance of combing rollers was 280 mm,the results showed that the threshing time was 1.73 s and the broken rate was 3.51%,which was the best.In order to study more deeply,the walking ability of indoor harvesting test bench was designed.Dynamic analysis of the harvesting process was carried out to study further on threshing mechanism and there are three factors,which are rotational speed,helix angle and travel speed,proved to be important to the harvesting.Then the orthogonal experiment was conducted.The evaluating indicator of this test were threshing rate and breakage rate,the factors of this test were rotational speed,helix angle and travel speed and the samples of this test were the Cabernet Sauvignon.This test showed that only rotational speed and travel speed can influence the threshing rate to a certain extent.With the increase of rotational speed from 200 r/min to 300 r/min,the threshing rate increased from 75%to 92.3%.With the increase of travel speed,the threshing rate decreased from 93%to 78%.Moreover,for the breakage rate,the three factors were not significant and the breakage rate maintains were about 20%.In order to improve the work efficiency and quality furturely,the experiment equipment of plate and saw teeth were designed and made.The comparison experiment of bow teeth,plate teeth and saw teeth was designed and executed.The threshing rate of the three kinds of devices were required to be the same threshing rate at different speeds.It was found that with the increase of speed from 0.4 to 0.5 m/s,the rotational speed of bow teeth,plate teeth and saw teeth decreased.At the speed of 0.6 m/s,the rotational speed of bow teeth and plate teeth were 260 r/min,and that of the saw teeth was 230 r/min.The breakage rate of the bow teeth and plate teeth increased with the increase of the travel speed,and the plate teeth was lower than that of the bow teeth.The breakage rate of the saw teeth was the lowest,which was stable at about 7.5%.Therefore,the saw teeth had high threshing efficiency and low damage rate.4.The obstacle avoidance control system based on PLC was developed for the automatic obstacle avoidance system.The touch control integrated host computer based on MCGS not only can realize the monitoring of the various parameters of the threshing process,but also can realize the manual operation system.The test proved that the obstacle avoidance can be carried out steadily and reliably... |
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