Design Method And Experimental Research On Self-propelled Corn Harvester For Hilly And Mountainous Region

Hilly regions are the main planting areas of com in China. However, the mechanized corn harvesting level in these areas is far lower than that in plain area in the respects of scale and rate. Considering this situation, this paper focuses on self-propelled corn harvester suitable for hilly regions. According to the results of adaptability tests and indoor test-bed experiments, the design principles of corn harvester machine were determined. Furthermore, the design method of self-propelled corn harvester was discussed based on the physical and mechanical properties of corn plant. Provided virtual prototyping technology, the vehicle and its snapping components were simulated. Finally, a self-propelled corn harvester for hilly regions was developed with field tests conducted.(1) The development trend, key technology and research methods of corn harvester were investigated basing on literature review and in-depth survey. The model parameters of major domestic corn harvesting machine manufacturers were then summarized. From the above, the objectives and the technical route of this paper were determined.(2) Through the classification and features of the existing domestic corn harvesters, we proposed the screening principle of corn harvester for hilly regions. Two small-scale corn harvesters were screened for adaptability test. From the results, the existing problems and key technologies of domestic corn harvesters in current situation were presented.(3) The multifunction test-bed for corn harvester was developed for feed-in as well as snapping tests of corn plant. The test-bed consists of the plant-feed-in mechanism, the multi-condition snapping and peeling units, measurement system for power consumption, and high-speed camera system. The plant-feed-in mechanism can simulate the feed-in state during harvesting with adjustable feeding speed, row-spacing, and plant-spacing. Similarly, the rotating speeds of picking rolling and husking roller are adjustable by adopting a frequency conversion motor. Meanwhile, the snapping angle and the gaps of the stretching rollers, husking rollers and the snapping plate can be adjusted quickly and conveniently. The power consumption test was carried out and the motion characteristic parameters of corn stalk and ear were analyzed with the high-speed camera. The experimental data provides support for designing the snapping mechanism.(4) Provided the measured physical dimensions of a certain type of hilly corn plant, a mathematical model of the corn plant associated with the key geometric parameters was formulated. On account of the experimental data and references, the bending, tensile, shear and compression properties of com stalk were studied. Consequently, we obtained the maximum values of the bending angle of corn stem, the tensile, shear, and extrusion failure forces of corn stalk. The mechanical properties of the grain bract and kernel were taken into consideration, and the friction characteristics between the plant and various materials were gained. The data describing the physical and mechanical properties of corn plant provides support for designing the snapping mechanism.(5) The design method of harvester chassis was proposed considering the walking mechanism of wheeled agricultural machinery and hilly terrain features. Correspondingly we determined the design schemes of the whole logistics module, the walking and transmission mechanisms. The design method of the key components of corn harvester were then studied based on the mechanical properties of corn plants. Given the bending, tensile, shear and compression properties of corn stalk, the design approaches of the divider, snapping and straw chopper units were proposed.(6) The simulation approach of key components for corn harvester was proposed in consideration of the analyses on force and kinematics during snapping process with application of virtual prototyping technology. The rigid-flexible model of corn stalk and ear were built on the mechanical properties of corn plant, which provides the key parameters used as simulation input. Then the interaction between the corn stalk and the machine key components, and the dynamic behaviors of the harvester traveling on various sloping grounds were simulated.(7) A type of4YZP-2self-propelled corn harvester was developed in collaboration with an agricultural machinery manufacturer. It has a length of3980mm (27%less than the average length of domestic two-line harvesters) weighing1680kg (34%less than the average weight of domestic two-line harvesters) with a22.98kW engine power. Its adaptability and reliability were verified through field trials and it is proved to be applicable to hilly regions according to the results.