| Potato is an important food crop,which is of great significance to increasing farmers’ income,helping poor areas win the battle against poverty,and ensuring national food security.In recent years,the planting area of potatoes in my country has gradually increased,but the degree of mechanization of potato harvesting is not high.Therefore,based on the agronomic requirements of potato harvesting and grading,this research proposes the technical idea of “translational conveying of the rod group,separation of the potato soil at the front end,and achieve grading by changing spacing at the backend end”,and designs a small potato conveying and grading device,which can realize potato conveying,potato soil separation,grading and collections.The main research contents and conclusions are as follows:(1)Design a potato conveying and grading device by using the scheme of conveying and grading combined working.Through the analysis the working objectives,the design requirements of the conveying and grading device are determined,and then the overall structure and working principle of the conveying and grading device are determined by comparing the differences between various conveying devices and grading devices.On the basis of investigation and experiment,the design of the conveyor chain,potato guide plate and collection box were completed,and the frequency analysis of the frame was also performed to determine that the frame would not resonate.(2)Carried out the mechanism research of conveying and grading.Analyze the movement trajectory of the potato on the conveying and grading device,and determine the value range of the inclination angle in stage I of upward to be 12°～32°.By analyzing the force of potato in the conveying and grading device,the factors affecting the potato upward movement were determined as the supporting force of the turning board to the potato,the distance between the turning board and the potato contact point to the potato centroid,and the angle between the turning board and the potato contact point and the potato.By analyzing the movement of potato in the grading stage,it is found that the larger the moment of inertia of the turning board,the smaller the radius of the turning board and the larger the position angle between the two turning board,the greater the extrusion force and friction between the potato and the turning board,and the greater the damage probability of the potato.(3)Determined the optimal structural parameters of the conveying and grading device.A discrete element simulation model of the interaction between the conveying and grading device and the potato was established.With the potato grading accuracy rate as the evaluation index,the simulation experiment was carried out by the combination of single factor and quadratic orthogonal rotation regression.The simulation results show that the primary and secondary factors that affect grading accuracy rate are conveyor chain speed,potato feed rate,conveyor chain elevation angle.The structural parameters of the conveying and grading device are optimized.When conveyor chain elevation angle is 13.74°,conveyor chain speed is 1.24 m/s and the potato feeding rate is 3.93 kg/s,the grading performance of the conveying and grading device is the best,and the grading accuracy rate is 93.5%.(4)Verified the field working performance of the conveying and grading device.The field test results showed that the working performance of the prototype was stable,the average grading accuracy rate was 88.06%,and the average potato injury rate was 1.97%.All test evaluation indicators can meet the agronomic requirements of potato harvesters. |
