Structure Simulation And Optimization Of Large Straddle-row Self-propelled Orchard Sprayer Based On Multi-body Dynamics

Orchard planting industry plays a very important role in China’s agricultural production.The development of orchard planting industry is inseparable from the wide application of plant protection machinery.Large cross line self propelled sprayer,as an advanced plant protection operation machinery,has been widely used in orchard planting in advanced agricultural countries because of its large spray range,high efficiency and good pest control effect.At present,the large cross line self propelled sprayer is mainly used for advanced standardized farms.The equipment is mainly imported.At present,this type of machine is seldom applied in the field of orchard plant protection in China,and the relevant design data are few.However,with the development of CAE technology,engineers can improve the design before the physical model is manufactured,and greatly reduce the production cost.Based on the structural analysis and optimization of the large span inter row self-propelled orchard sprayer,the multi-body dynamics method based on the finite element method is used to analyze the structural mechanical properties of the large span inter row self-propelled orchard sprayer in this paper,and the analysis and improvement of the frame structure components are carried out,so as to provide technical reference for the design and development of the large-span inter row self-propelled orchard sprayer.The main results are as follows:(1)The 3D assembly model of large cross line self-propelled orchard sprayer was built by using the 3D modeling software Solid Works.The model was simplified according to the structural characteristics of the orchard sprayer frame,and the solid unit was simplified as the surface unit.According to the motion principle of the orchard sprayer mechanism,the motion relations among the parts were determined,and the boundary conditions such as constraints and loads were added.Finally,a multi-body dynamics finite element model of large-scale inter row self-propelled orchard sprayer is established.(2)The static performance analysis of the frame of large span inter row selfpropelled orchard sprayer is carried out.The mechanical properties of the orchard sprayer frame under three typical working conditions of full load bending,limit torsion and emergency automation are analyzed.The results show that the maximum stress value of the frame appears under the condition of ultimate torsion,the maximum stress value under this working condition is 309.14 Mpa,but less than that of Q345 steel.The overall structural strength basically meets the use requirements,and there is stress concentration at the ear plate of the supporting frame under three working conditions,which needs to be improved.(3)The free modal analysis and prestress modal analysis of the frame of large span inter row self-propelled orchard sprayer are carried out.The first twelve order prestressing modes of the whole structure and the six order prestressing modes of the non sprayer frame are extracted respectively,and the obtained modal analysis results are compared with the main rotational excitation frequencies of the engine.There is a big difference between the natural frequency of the frame and the exciting frequency of the engine at idle speed and rated speed,so the frame will not appear resonance phenomenon.In this study,the modal superposition method is applied to carry out random vibration analysis of the orchard sprayer frame.The road surface spectrum of the D grade road is load input.The results show that there is obvious stress concentration phenomenon at the connecting rod of the boom,which will affect the fatigue life of the orchard sprayer frame.In order to verify the above results,the vibration test of orchard sprayer frame is carried out.The test results show that the frame has no obvious resonance phenomenon,and the frame vibration is mainly caused by engine rotation excitation,which verifies the accuracy of the above analysis.(4)The transient multi-body dynamics analysis of the large span inter row selfpropelled orchard sprayer was carried out,and the tire stiffness damping model was established.Through the load displacement load on the right wheel,the unilateral obstacle surmounting condition of the orchard sprayer was analyzed.The results showed that when the front wheel of the sprayer frame began to block,the overall structure of the frame increased vibration,before the end of the front wheel crossing obstacle and the rear wheel crossing obstacle,The vibration of the frame structure is attenuated.When the rear wheel starts to cross the obstacle,the vibration of the frame structure is strengthened again,and the spray bar shows reciprocating motion in the process of crossing the obstacle,which is basically consistent with the state in the actual operation process.Based on the above mechanical analysis,the frame structure is improved to reduce the stress concentration and improve the stress distribution.