| In order to improve and optimize the header of the crawler type wide foldable rape windrower under field conditions,which affects the operation performance,cutting and tanning performance and service life of the machine,the research takes the header of this model as the research object,analyses the influence of various excitation sources on its vibration,searches for the main structural vibration transmission path.The aim is to improve and optimize the structure of the header in order to improve its rigidity and strength and reduce its working amplitude.The main research components and conclusions are as follows:(1)An improvement of the traditional OTPA method based on the singular value threshold selection principle.(1)A five-excitation single-response vibration analysis model of"excitation-transfer path-response"was designed using ADAMS software,and a comparative test analysis showed that the improved OTPA before and after could reproduce the simulated signals well.(2)The results show that the predicted MAPE value of the contribution of the improved OTPA method to the dominant path in this numerical example model is reduced from 0.97 to 0.37,indicating that the improved OTPA method can improve the accuracy of predicting the contribution of the dominant path at the characteristic frequency point while ensuring the overall prediction accuracy.The results are closer to the actual simulation values.(2)An analysis of the excitation characteristics of each excitation source under the operating conditions of the crawler type wide foldable rape windrower was carried out.(1)The excitation frequencies of each excitation source were 6.56Hz,0.71Hz,4.46Hz and 36.67Hz respectively.(2)The results showed that the cutting device was the main vibration excitation source of the header system.(3)The vibration contribution of each excitation source on the oilseed rape header was analyzed,and the results showed that the order of influence of each excitation source on the header frame vibration during operating conditions was:cutting unit,paddle wheel unit,and conveyor unit.In the frequency point of the maximum vibration of the cutting table,the cutting devices on the left and right sides contributed 69.56%and 70.24%respectively of the total vibration response of the respective header.(3)A vibration simulation was carried out on the header of the crawler type wide foldable rape windrower based on Recurdyn software.(1)The multi-body dynamics model of the harvester was established and the simulated vibration characteristics of the frame response points of the harvester were compared with the measured vibration characteristics.(2)The modal characteristics of the header frame were analyzed based on ANSYS Workbench.The results showed that the first order modal frequency of the header frame was 25.77Hz,while the excitation frequency of the cutting device was6.56Hz under the tanning operation,and the fundamental frequency of the header frame was near the multiplier frequency generated by the cutting device,which means that the cutting device could easily resonate with the header.(4)An optimization of the vibration path structure of the header frame was carried out.(1)The relationship between the support beam and steel thickness of the header frame and the first-order intrinsic modal frequency and maximum amplitude of the header model was established through a four-factor,four-level test.The test results showed that the major and minor factors affecting the first-order modal frequency of the header frame were:vertical beam,inclined beam,longitudinal beam and cross beam,respectively;the major and minor factors affecting the maximum displacement of the header frame were:vertical beam,inclined beam,cross beam and vertical beam,respectively.(2)The optimum combination of the header structure was found when the thicknesses of the vertical beam,vertical beam,inclined beam and cross beam were 2mm,2mm,2mm and4mm respectively,and the static test showed that the maximum stress on the cutting table frame was 100.75MPa,which was less than the permissible material stress,and the maximum deformation of the frame was reduced from 8.36mm to 3.90mm.It has been increased from 25.77Hz to 28.80Hz to avoid resonance problems with the cutting unit.(5)A vibration simulation of the optimized cutter deck was carried out.Analysis of the vibration of the optimized model using Recurdyn software under target conditions showed that the overall amplitude of the optimized mechanism was controlled,with the amplitude of the transverse cutter section on the left-hand side of the cutter reduced from7.17m/s~2to 3.37m/s~2,a reduction of 55.8%.This optimization has effectively improved the overall vibration of the header. |
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