| In agricultural production machinery equipment,paddy field grader is an important mechanical equipment for leveling paddy field.The flat paddy field can meet the operation requirements of high flatness of paddy field,such as rice direct seeding machine and rice transplanter.In the operation of paddy grader,the height and levelness of the flat shovel can be adjusted.The three-point suspended beam and two-link structure play an important supporting and guiding role in the process of the flat shovel movement of paddy grader.Due to the flexibility of the beam material and the large span of the design,it is easy to produce vibration deformation.The coupling between the bending vibration deformation of the important flexible components and their overall rigid movement makes the paddy field grader exhibit strong rigid and flexible coupling characteristics.The systematic analysis of the vibration of the rigid-flexible coupled paddy grader is an important premise to further optimize the flexible structure and improve the stability and control response of the paddy grader.This research group is committed to the research and optimization of paddy field laser grader,but in the previous vibration analysis research,the beam and two connecting rods are regarded as rigid bodies,and the vibration deformation of flexible components is not considered systematically.In the paddy field grader beam,two connecting rod structure as a rigid body can’t systematically reflect the problem of the coupled vibration characteristics of the in paddy field grader actual project as the background,based on ANSYS and ADAMS,the coupled simulation analysis,put forward a kind of the beam,two connecting rod as a flexible body and systematically on the coupled vibration analysis method of rice grader,the main research content is as follows:(1)To solve the problem that the boundary condition of beam in paddy field grader is complex and the natural frequency is not easy to be solved,a natural frequency calculation method is proposed after reasonable simplification based on euler Bernoulli beam theory and assumed mode method.Firstly,according to the structural characteristics of the beam,it can be regarded as eulaboulli beam,and the method of expressing the form of load beyond the constraint of the beam by using eulaboulli beam theory and assumed mode method is adopted to analyze the boundary conditions of the beam and construct the vertical mode equation,so as to obtain the first two natural frequencies conforming to the boundary conditions of the beam.(2)In order to obtain the structural characteristics and modal parameters of the beam in the paddy field grader,the finite element simulation of the beam was carried out.According to the simplified boundary conditions of the beam in theoretical modeling,the static simulation of the beam is carried out first to obtain the strain and stress.Based on this,the stiffness and strength of the beam are analyzed.Then the first six natural frequencies and mode shapes of the beam are obtained by modal simulation.By comparing the natural frequency obtained by simulation with the first order natural frequency obtained by theoretical calculation,the relative error of the lowest natural vibration frequency is 0.33,which verifies that the theoretical analysis modeling can well meet the requirements of calculating the lowest natural frequency.In addition,the calculation of the natural frequency of the beam can be used as an important contrast parameter to judge whether the beam will resonate.(3)In order to obtain the vibration response of the beam in the process of leveling shovel elevation and horizontal movement and the main frequency band of external excitation force,ADAMS,a dynamic simulation software,was used as a platform to conduct rigid-flexible coupling modeling and simulation for the vibration response of the beam in the process of leveling shovel height and horizontal adjustment.SolidWorks is used to carry out accurate3 d modeling of paddy field grader and introduce it into the software.ANSYS is used to replace the original rigid body with the beam and two connecting rods after the flexible treatment.Finally,the rigid and flexible coupling paddy field grader simulation model is obtained.The vibration response of the beam in the process of flat shovel motion was obtained by simulation,and the maximum amplitude of the beam along the X-axis and the maximum amplitude of the mark point at the end was 2.57 mm when the beam was adjusted horizontally.Fourier transform the external excitation force,the main frequency bands of the external excitation force of the beam are all 0～ 1.5Hz.By comparing the natural frequencies in the modal parameters,it is concluded that the beam will not resonate.In addition,the stress curve of the hinge point between the beam and the flat shovel is obtained through the dynamic analysis.When the flat shovel is lifted,the hinge point is subjected to the maximum force along the z axis,with the size of 2100 N.This force can be used as the maximum load force on the hinge point between the beam and the mounting frame,providing reference for the later structural optimization.(4)In order to verify the accuracy of the model simulation results of paddy field grader,the model simulation results were verified experimentally based on the measurement method of binocular high-speed camera.The same global coordinate system as that in the simulation software is established,and the motion state of the beam and the shovel-mark points is measured experimentally with binocular high-speed camera and compared with the simulation results.During horizontal adjustment of flat shovel,the maximum absolute error of displacement along the axis of the marked point on the flat shovel is about 3.5cm and the relative error is 2.92%,which verifies that the simulation can better reflect the true movement trajectory of the flat shovel during horizontal adjustment.When the leveling shovel elevation is adjusted,the maximum displacement error of the mark points on the beam moving along the axis is about 2.4cm and the relative error is 5.10%,which verifies that the simulation can better reflect the real movement trajectory of the beam when the leveling shovel elevation is adjusted.Comparing the vibration response of the mark points along the axis of the beam with the horizontal adjustment can better reflect the real vibration frequency of the flexible beam.The simulation results of rigid-flexible coupled paddy field grader are verified by experiments.Based on ADAMS and ANSYS the coupled vibration analysis studies rice grader,reasonable division and comprehensive consideration of mechanical equipment and soft component in stiffness and strength of the flexible components,modal parameters and vibration response,systematically analyze and compare the vibration of the main factors,the accuracy of the simulation results is verified by the experiments,can better reflect the coupled vibration characteristics of rice grader.This reliable vibration analysis and research method is not only applicable to the vibration analysis and research of paddy field grader,but also can be used in the research of industrial automation production equipment,robots and other precision equipment. |
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