Research On FEM Modeling And Vibration Control Of Spray Boom Of Plant Protection Machine

For a long time,the chemical control of crop pests and diseases in the field has become a major problem to be solved in the agricultural production process.Research at home and abroad has found that when the boom sprayer is operating in the field,the unevenness of the ground will cause horizontal and vertical vibrations of the boom,which will deviate from the normal movement posture and affect the uniformity of application.Therefore,establishing the elastic boom position model and suppressing the elastic deformation caused by the vibration of the boom are the key to the uniformity of the spray distribution and the improvement of work efficiency.For the purpose of exploring and suppressing the elastic deformation in the vertical direction of the boom,the corresponding research work has been carried out.In response to this problem,on the basis of reading a large number of Chinese and foreign literature,the research status of plant protection machinery at home and abroad was analyzed,and the shortages in the research of plant protection machine’s spray bar were summarized.In this thesis,a finite element analysis method of the boom is introduced in detail,and the dynamic finite element model of the boom is established.The boom is discretized,the displacements of each node are analyzed by dividing elements,and the displacement interpolation function is obtained.A appropriate transformation matrix is selected to establish the global generalized coordinate array,and each unit is linked.The dynamic equations of the entire boom are established..Based on the established model of boom dynamics,a more comprehensive theoretical analysis of boom vibration was performed,the theory and method for solving the multi-degree-of-freedom elastic body vibration and the natural frequency of the boom are further analyzed.Based on the theoretical analysis,the modal analysis of the boom was performed using the software ANSYS.The vibration modes of the boom were studied under free vibration conditions,and the node with larger degree of deformation of the boom under the low-frequency vibration was determined.Based on the analysis of ANSYS,under the initial disturbance,the nodes that match the experimental requirements were simulated,and the vibration of the boom was simulated by MATLAB to obtain the corresponding response graph of the vertical direction of the nodes.By comparing the displacement diagram of each node in the vertical direction,it was found that the degree of deformation of the 13 node in thevertical direction is the largest,and the vertical displacement of nodes is used as a standard for judging the effectiveness of control.Then a linear quadratic optimal control method was used to design the optimal controller to control the elastic deformation in the vertical direction of the boom,and simulate different nodes as the end deformation of the boom when the control force is applied.The contrast control effect,select node 5 as the final appropriate control force application point,and finally find the optimal control force.The simulation results show that the optimal controller designed in this thesis has a good inhibitory effect on the vertical vibration of the spray boom of the plant protection machine.At the same time,the selection of the control force application position provides a method for engineering implementation.