香蕉落梳机气动夹持部件参数优化与试验

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

目前香蕉采收处理对蕉穗的夹持一般采用尖锐部件插入果轴的方式,导致卸荷后果轴不能自动脱离夹持器,不利于实现香蕉落梳机械化和自动化。针对上述问题,设计出气动夹持装置和弧形夹持部件,分析了夹持部件与果轴间的相互作用关系,确定了影响夹持部件与果轴间当量摩擦力的关键因素。试验结果表明夹持部件材料、夹持部件内弧面面积、果轴直径和气缸气压4个因素对当量摩擦力具有显著性影响(P<0.05);对当量摩擦力影响的主次顺序依次为夹持部件材料、夹持部件内弧面面积、气缸气压、果轴直径。正交试验回归分析表明采用橡胶夹持部件,内弧面面积为1 885 mm^2,气缸气压为0.5 MPa,果轴直径为69 mm时当量摩擦力最大,为359.494 N,实测值为375.975 N,与回归分析结果无显著性差异。该研究可为茎杆类植物体夹持方法和夹持部件的改进与应用提供参考。

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＆lt;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 1 885 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.