Optimization of operating parameter and structure for corn ear picking device by bionic breaking ear hand

Abstract: In China, the planting area of corn was expanded to 3676 million hm2, which accounted for about 32.5% of the national planting area of corn by 2016. And its output reached 21955 million tons in the same year. Corn has become the first crop in place of wheat and rice for many years. Mechanical grain harvesting has been the developing direction of corn harvesting technology. In addition, the production and processing of fresh maize are rapidly developing and gradually walking up to the industrialization. Now the fresh maize harvesting mechanization is still backward in China. Grain harvesting and fresh maize harvesting both require low damage to corn ears. In recent years, corn harvesters have been developed rapidly with the improvement of the subsidies on agriculture. However its low level of mechanical harvesting is unable to meet the requirement of low damage and therefore has restricted the development of corn mechanical harvesting compared to other crops. The high loss rate, high impurity content and high damage rate of the traditional snapping type harvester, including snapping rollers type, snapping plate type and their combined type, have been the choke points of combine harvester development because of extrusion or nibbling on the corn ear for a long time. According to investigation, the study of bionic corn ear picking is rare abroad, and the research institutes mainly study the principle of snapping corn ear at home, which is only the theoretical study. So a new way to pick up corn ear is needed urgently. In order to solve these problems, our research team has designed the bionic device of breaking corn ears, studied the speed of bionic hand of breaking corn ear and carried out the experiment on power consumption. To verify the feasibility of low damage harvesting, the test device was built, which included bionic device of breaking ear corn, pulling stem device and clamping feeding device, and the whole structural working mechanism of the machine was introduced in detail in this research. The structure parameters of main operation components were determined at last. The theoretical design and mechanical analysis of the mechanism were carried out. In order to confirm the operation parameters of the bionic hand device of breaking corn ear, the Box-Benhnken central composite experimental design principle was adopted with 3 levels and 3 factors. Three test parameters, i.e. number of breaking-ear hands, speed of breaking-ear hand and clamping guideway speed, were chosen as the influence factors of test experiment. And corn grain loss rate was selected as the response index of test experiment. In the experiment, quadratic orthogonal rotation combination trial design was applied to build the quadratic polynomial regressive model, which interpreted the relationship between the experimental influence factors and evaluation index. According to theoretical analysis, the breaking-ear hand number was selected from 1 to 3, the breaking-ear hand speed from 0.95 to 2.85 m/s, and the clamping guideway speed from 0.83 to 1.67 m/s. Using the data analysis software Design-Expert 8.0.6, the matching mathematical regression pattern was developed, the relation of salient factors with the evaluation index was analyzed, and the parameters of the test were optimized. The results showed that the significant effects of breaking-ear hand speed, breaking-ear hand number and clamping guideway speed on grain loss rate were in a decreasing order. The best work parameters were as below: When the breaking-ear hand number was 2, the breaking-ear hand speed was 2.15 m/s and the clamping guideway speed was 1.14 m/s, the corn grain loss rate was 0.031%. Bench experiments were carried out with the above optimized parameters, and the corn grain loss rate was 0.04%. The relative error of evaluation index and theoretical optimization value was only 0.009%. It was found that bionic device of breaking-ear hand had good performance, and the corn grain loss rate was less than the national industry standard (2%) and also less than the traditional snapping roller. The research results can provide the references for low damage corn harvesting technology.