| Fresh corn is an essential component of China’s corn industry,and it is widely planted nationwide.The southern and southwestern regions are significant fresh corn-producing areas.Due to the limitations of hilly terrain and planting agronomy,cob picking in this production area is still manual,and mechanization is far lower than the national average machine harvest level of corn.Current fresh corn harvesters can only harvest corn cobs and are not equipped with stalk processing devices,significantly reducing the value of fresh corn stalks.In order to solve the challenges of a lack of fresh corn-specific harvesting machinery,significant damage from header picking,and difficulty in crushing and recycling straw,research on the critical technologies for fresh corn header harvesting stalks and cobs are presented in this study.The study’s details and conclusions are as follows.(1)Design on fresh corn header for harvesting stalks and cobs.The research object was Lu Cainuo No.8 fresh corn,which is widely planted in Ya’an City,and its agronomic,physiological characteristic parameters,and machine harvesting requirements were examined.The general structural solution of a fresh corn header for harvesting stalks and cobs and a theoretical study of the rack,transmission system,and auxiliary working component is proposed.The ANSYS software is used to analyze the header rack’s constraint modal.According to the analysis results,the number of modal frequencies of the rack frame’s first six orders is 10.143～23.921 Hz,and the vibration source frequency explicitly avoids each order’s frequency.(2)Research on the mechanism of low-damage bionic picking.The mechanical properties of fresh corn kernels were tested,and the results showed that the maximum breaking forces of the cob’s bottom,middle,and top kernels are 31.55 N,34.45 N,and 23.40 N,respectively.Based on the manual picking principle,a bionic picking device with dislocated picking roller was designed.When a 10 mm dislocation picking roller is compared to a non-dislocated picking roller,the deformation of the cob stem position is 28.8% greater,the strain of the cob is 38.9% lower,and the stress is 48.7% lower.It can be seen that the dislocation picking roller has apparent advantages for low-damage picking.(3)Bionic picking simulation optimization test based on ADAMS.The maximum contact force of the picking cob was used as the test index,while the picking roller gap,the picking roller tilt angle,and the stalk speed were used as the test factors.The test showed that the impact of the factors on maximum contact force is in the following order: stalk speed>picking roller gap>picking roller tilt angle.The optimal operation parameter combination is: 40.6° picking roller tilt angle,25.0 mm picking roller gap,and 338.1 mm/s stalk speed.The maximum contact force under these conditions is 525.4 N.Based on the theoretical analysis results,a bionic picking device test bench was created,and the parameter combination was rounded and tested on the bench.The test revealed that the bionic picking device has a damage rate of 0.32%,which meets the requirements of a low-damage picking operation for fresh corn.(4)Research on stalk differential-speed crushing device.The geometric features of the leaf-cutter ant’s mandible were analyzed using reverse engineering technologies,and the bionic blade edge curve was designed based on the mandible slip-cutting curve.The simulation and bench comparison tests revealed that the bionic blade has clear advantages in increasing the flatness of the stalk cutting surface and lowering the maximum cutting force.Based on the bionic blade,the stalk differential-speed crushing device was designed,and essential components such as the stalk kneading device,stalk collecting stirrer,and throwing device were theoretically studied.The wind field of the throwing device simulation study showed that the airflow velocity at the top outlet of the throwing device is greater than the suspension velocity of the stalk,and the stalk can be blown out of the sprinkling device.(5)Stalk differential-speed crushing device bench optimization test.The qualified rate of stalk length was used as the test index,while the kneading roller speed,collecting stirrer speed,and crushing shaft speed was used as the test variables.According to the test results,the impact of the factors on the stalk length qualifying rate is as follows: crushing roller speed > collecting stirrer speed > kneading roller speed.The best settings for the stalk crushing device are 780 r/min for the kneading roller,380 r/min for the collecting stirrer,and1060 r/min for the crushing shaft.The qualifying rate of stalk length under this circumstance is 87.0%,which fulfills the design criterion. |
