Parameter optimization and experiment of pneumatic holding part for banana crown cutting

Banana is one of the most important crops in the world, and ranks the fourth after rice, wheat and maize with annual production of more than 106.71 million tons in about 136 countries and regions in 2013. Banana postharvest treatments consist of collection, transportation, crown cutting, cleaning and sterilizing, packing and storage. Banana crown cutting is one of the central tasks for banana postharvest treatments. In this treatment, banana stalk is fixed and cutting tool is used to separate bananas from banana bunch. The mechanization application level of banana postharvest treatments is relatively high abroad and the well-found lossless harvest system has been established. But there is no research result of banana crown cutting machine. Rapidly developing banana industry in China in recent years made banana production reach a record of 12.37 million tons in 2013 which contributed to about 11.6% of the world's banana production. The construction of banana postharvest treatments' infrastructure facilities and the mechanization application level are relatively backward in China. Excessively low level of mechanization causes more than the banana loss of 1 million tons every year in China. So the research of banana crown cutting machine is particularly significant to banana industry both in China and abroad. The existing banana stalk clamping devices hold banana stalk by inserting sharp edge part into fruit axis of banana in banana postharvest treatments. In this way, banana stalk must be removed by manual operation, in which banana stalks can't be loaded and unloaded one after another automatically. So those devices cannot be applied to banana crown cutting machine. This paper designed pneumatic clamping device, traction tray device and curved holding part to solve the above problems. The pneumatic clamping device is mainly composed of pneumatic system, straight-line moving mechanism and installing module of holding part. The clamping force is perpendicular to the axis of banana stalk and it can be regulated by adjusting the pressure of air compressor. The traction tray device is mainly composed of metal pole and tray. It is used to fix banana stalk tightly to tensile strength sensor and prevented it from axially slipping in tests. Tension tests of banana stalk samples clamped by pneumatic clamping device were done on the personal computer controlled electronic universal material testing machine. The relations of interaction between the holding part and the banana stalk were discussed in this paper. The results of single factor experiments showed that material of holding part, inner arc surface area of holding part, diameter of banana stalk and cylinder gas pressure had significant effect on the equivalent friction (P<0.05) between the holding part and the banana stalk. Results of multifactor orthogonal experiments showed that the influence sequence of experimental factors from high to low was material of holding part, inner arc surface area of holding part, cylinder gas pressure and diameter of banana stalk. Linear regression analysis of orthogonal experiments results showed that the equivalent friction increased significantly to a peak value of 359.494 N when using rubber holding part with inner arc surface area of 1885 mm2, banana stalk diameter of 69 mm and cylinder gas pressure of 0.5 MPa. There was no significant difference in equivalent friction between linear regression analysis result and actual value that was 375.975 N (P<0.05). These researches are helpful for the design of banana stalk clamping device in banana crown cutting machine and are also beneficial to the improvement and application of clamping methods and clamping devices for stemmed plants. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.