Development Of Portable Mower In Orchard Based On Computer Simulation

At present,the advantages of the orchard grass cutting technology are becoming more and more prominent with the increase of fruit production and the improvement of planting area of orchard,the traditional "Qing tillage system" has gradually withdrawn from the stage.Mechanized equipment is needed for orchard management to improve work efficiency and emancipate the labor force,and most mowers are only suitable for orchards in plain area or lawn mowing.In order to reduce the loss of mowing in orchard effectively and improve the efficiency of mowing,an orchard lawn mower with two disk was developed,which is suitable for small orchard in mountainous areas of China,and based on the physical and mechanical properties of Medicago sativa and the research status of the cutting machine at home and abroad.The contents and conclusions are as follows:(1)According to the situation of orchard and the requirement of cutting performance,the design principle of the portable lawn mowing machine for orchard is defined.According to the design principle,the overall structure of the cutting machine is determined,including the gasoline engine power system,the belt and gear transmission system and the front double disc cutting system.By analyzing the cutting mode and principle of the cutter,it is determined that the number of cutter head is 2 pieces,the diameter of cutter head is 400 mm,the length of blade is 50 mm,and the blade is 4 pieces on each cutter head.The modal analysis of the cutting device is carried out by workbench,and the critical speed of the resonance is 7170 r/min,which provides the basis of avoiding the bending vibration in the actual work.(2)Medicago sativa,one of the perennial legume grasses,was selected as the research object.The tensile,shear,compression and bending mechanical properties of the Medicago sativa stem were analyzed,and the mechanical parameters of the Medicago sativa stem were summarized.The elastic modulus of Medicago sativa stems was about 37.79 MPa,the compression modulus was about 101.3 MPa,the flexural modulus was about 9.6 MPa,and the maximum shear strength was about 9.21 MPa.(3)The finite element analysis of the cutting process of single Medicago sativa straw was carried out on ANSYS/LS-DYNA.The influence of the different working parameters of the cutting machine on the stress and the cutting resistance during the cutting process was studied.The result is that the increase of the cutting speed will cause the increase of the root stress of the Medicago sativa stalk,which may break the root and be unfavorable to regrowth;when the speed of rotation is too fast or too slow,it will be unfavorable to cutting the blade,which will easily cause radial vibration of the blade.(4)The influence of cutter motion parameters on the rate of cut and leakage was studied.On the basis of analyzing the structure of double disc rotary cutter,the motion simulation of virtual prototype was carried out by using ADAMS software,and the movement track and cutting area diagram of cutter were studied.The optimum combination of cutting speed,blade rotation speed and number of blades was obtained by orthogonal test,with recut rate and the leakage rate as the evaluation index.The forward speed is 2.74 km/h,the rotation speed is 2000 r/min,and the number of blade is 3 slices.(5)After the prototype test in the field,it is found that the recut rate and the leakage rate of the blades are reduced by 5.83% and 1.1% respectively after optimization of the motion parameters,compared with those before the optimization.Therefore,the test results are agree well with the simulation ones.