Design And Test Of Double-roller Sweet Potato Vine Harvester

Sweet potato vines have large yield and rich nutrition,so they are ideal feed materials.However,the sweet potato vines are intertwined and creeping.If manual harvesting is adopted,the labor intensity is very large.Therefore,it is of great significance to develop a device that can realize the mechanized harvesting of sweet potato vines to promote the sustainable development of the sweet potato industry.In this paper,through the measurement and analysis of the biological characteristics and material characteristics of sweet potato vines and the theoretical analysis of the key devices of the sweet potato vine harvester,a discrete element bonding model of sweet potato vines has been established and the simulation analysis of key devices has been carried out.Using the Box-Behnken experimental design method,a quadratic regression orthogonal experiment has been carried out,the influence of various factors on the evaluation index has been analyzed,and the experimental factors have been optimized and verified.Combined with the planting mode of sweet potato in Shandong Province,a double-roller sweet potato vine harvester was finally developed based on the front roller picking and rear roller cutting and rod-rod lifting structure,which can complete the harvesting operations of picking,cutting,sending and collecting vines at one time.The main research content and results are as follows:（1）The geometric dimensions of the sweet potato vines were measured by the tool ruler measurement method;the density of the sweet potato vines was measured by the drainage method;the moisture content of the potato vines was measured by a DHS-20A electric moisture meter;using the EZ-SX texture analyzer to measure the maximum shear force and tensile force of sweet potato vines,and the shear modulus,elastic modulus and Poisson ratio were 3.35 MPa,8.6 MPa and 0.28 respectively;The calibration test of the bonding parameters of the discrete element model of the sweet potato vines was carried out,and the reference values of the four bonding parameters of normal stiffness per unit area,tangent stiffness per unit area,critical normal stress and critical tangent stress were 7.50×10⁹ N/m^-3,5.59×10⁸ N/m^-3,60 MPa and 7MPa respectively.It provided a theoretical basis and data reference for subsequent discrete element modeling of sweet potato vines,simulation analysis of various system components,and determination of key structures and parameters of the prototype.（2）Based on the sweet potato planting mode in Shandong Province,a double-roller sweet potato vine harvester in the form of front roller picking vines,rear roller cutting vines,and pole lifting structure was designed.The machine is mainly composed of vine picking device,vine cutting device,vine sending and vine collecting device,and can complete vine picking,vine cutting,vine sending and vine collecting and harvesting at one time.The theoretical calculation and mechanical analysis of the structural parameters and working parameters of the key devices determined that the rotation speed range of the vine picking roller was 550-800 r/min;the vine cutting knife adopted an improved L-shaped knife,and the rotational speed range of the vine cutting roller was 1600-2200 r/min;the pole-type elevator width was 900 mm,length was 1150mm,pole spacing was 30 mm.（3）Based on EDEM,the simulation analysis of vine picking,vine cutting,and vine sending devices was carried out to determine the influence of structural parameters on the working efficiency of each device in the working process.Firstly,two kinds of sweet potato vine and tendril models with different attributes were established,and then the simulation analysis of each device was carried out.The results showed that the vine picking rate was the highest when the picker bar was inserted into the vines at a depth of 25 mm and the inclination angle of the end was 160°.It was determined that the length of the picker bar from the outside to the inside is 175 mm,150 mm,and 105 mm respectively,and the inclination angle of the end of the picker bar was 160°.With the increase in the number of vine cutting knives and the number of vine cutting discs,the qualified rate of sweet potato vines cutting has increased significantly.Therefore,the cutting device has been determined to be 13 discs and 6 knives.The harvest rate of sweet potato vines increased with the increase of the conveying speed.When the conveying speed was greater than 1.5 m/s,the harvest rate increased rapidly.When the conveying speed was greater than 3 m/s,the harvest rate increased slowly;when the conveying speed was constant,the harvest rate of sweet potato vines decreased with the increase of conveying inclination angle.When the conveying inclination angle was greater than 50°,the harvest rate of sweet potato vines was lower than 90%.Therefore,it was determined that the conveying inclination angle was 50°and the conveying speed was 3 m/s.（4）Field experiments were conducted to determine the optimal working parameters of the double-roller sweet potato vine harvester.The rotational speed of the vine picking roller,the rotational speed of the vine cutting roller and the ground clearance were selected as the experimental factors,the harvest rate of sweet potato vines,the stubble height,and the rate of damaged potatoes were selected as evaluation indicators,and the quadratic regression orthogonal test scheme was designed by using the Box-Behnken test principle.The results showed that the contribution rate of the three factors to the harvest rate of sweet potato vines was the speed of cutting roller>the speed of picking roller>the ground clearance;the contribution rate of the three factors to the height of stubble was ground clearance>the speed of cutting roller>picking Vine roller speed;the contribution rate of the three factors to the potato injury rate was ground clearance>vine cutting roller speed>vine picking roller speed;the speed of picking roller was 716 r/min,the speed of vine cutting roller was 1960 r/min,and the ground clearance was 16mm.It was the optimal parameter combination.After experiments,the average value of the experiment was basically consistent with the optimal value.The sweet potato vine harvest rate was 93.1%,the stubble height was 29.5 mm,and the sweet potato injury rate was 0.174%.