Design and experiment of wine grape threshing mechanism with flexible combing striping monomer

Abstract: 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. The old harvesting method restricts the widespread popularization and planting of wine grapes. Research on picking machine and picking mechanism of wine grapes is in its infancy in China. A study was conducted to change the artificial harvesting status of the wine grapes, promote the mechanization of the wine grapes thread mechanism, and establish the theoretical guidance and design basis for the picking machine of wine grapes for Chinese national conditions. First, a new-type wine grape thread mechanism by flexible combing striping mode was designed. The mechanism mainly consists of the multiple flexible pole teeth, a pair of combing rollers and a supporting power control system. The flexible pole teeth are the core component. It is U-structure and consists of the steel wire rope and silicone tube. The steel wire rope can change the bending stiffness of the flexible pole tooth by change its diameter. The silicone tube sleeves the steel wire rope, which can reduce the harm on grapes, and increase the friction between grape berries and the pole teeth. At the same time, the flexible pole teeth are fixed on a pair of counter-rotating combing rollers in a certain way. When the mechanism works, it threads the grapes by the flexible pole teeth. The main threshing form of grapes is that the grape brush pulls out from the grape berry. Second, for an in-depth analysis of the stripping mechanism, the parameterized model was established, and the flexible simulation model of the flexible pole teeth and stalks, which are discrete rigid bodies through a flexible BUSH connection, was built. By using the generalized force to establish the connection force between grape berry and stalk, and the sensor to monitor fracture condition, the grape threshing process was realized under the action of external force control, which solved the key problems of threshing simulation process control of multiple objects. The influences of three factors, i.e. the rotational speed, the bending stiffness and the distance of rotary shafts were analyzed through the simulation during the wine grape threading process. And it was found that they all could influence the threading process in certain degree. Last but the most important, based on the above simulation and analysis, the rotational speed, the bending stiffness and the distance of rotary shafts were taken as the orthogonal test factors. The rotating 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 of 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 results showed that there were some errors between the actual and the simulated experiment results, which needed the further research. The flexible pole tooth's bending stiffness was the only significant factor for the index of breakage and threshing time. In addition, the effect of the bending stiffness on wine grape picking was analyzed by the experiment. When the rotating 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.