Analysis of vibration characteristics and its major influenced factors of header for corn combine harvesting machine

Abstract: As a key component of combine harvesting machinery, the vibration characteristics of header play an important role to header frame structure and working performance. It not only needs to accomplish the operation of harvesting crops, but also is demanded to bear the function of supporting some parts, such as pick roller, conveying chain, gearbox and load box. At the same time, the performance of the header during operation will affect the vibration, noise and comfort directly. The interaction force between picking mechanism and crop during operation of corn harvesting machine, and the inertia force caused by dynamic unbalance of header and rotation motion of drive system, would lead to the failure of header. Therefore, vibration characteristics of header are very important for the design of corn combine harvester. In view of the problem of severe vibration and high failure rate during the operation of corn combine harvester, the dynamic vibration characteristics and the effects of header were investigated in this paper. Taking the header of corn combine harvester machine as research object, firstly, finite element model of header frame was established and its free mode was calculated. At the same time, the vibration test and modal experiment of header were carried out. Using eight-channel 24 bit INV3018C dynamic test acquisition instrument, the modal parameters and vibration modes were identified by the ERA (eigensystem realization algorithm). Secondly, the accuracy and reliability of finite element model were verified by the modal test. On the basis of the finite element model, the constraint mode of the frame was calculated. By means of time domain and frequency domain analysis method, the regulation of vibration amplitude characteristics, main vibration direction and frequency distribution of header in idle condition, transportation condition and field harvesting operation condition were obtained. Finally, the influence factors of header and the corresponding relationship between vibration frequency and modal parameters were analyzed. The changing regularity of vibration mode excited by vibration frequency was pointed out. It is shown that, the first order mode frequency is 27.260 Hz, the 2-10 order modal frequency ranges from 34.311 to 126.035 Hz, and the mode shapes are mainly bending modes and torsional modes. In addition, the working frequencies of spindle of header (28.77 Hz), chopping cutter (29.63 Hz), and field returning machine (43 Hz) all fall within the first 10 order modal frequency range. During the 3 conditions (idle speed, transport and field harvesting), the vibration differs by an order of magnitude between the operating of working parts and the engine operating only, which indicates that resonance has occurred in header. The main factors causing the vibration of header include the 2 order firing frequency of engine (76.25 Hz), road excitation frequency (1.5 or 2.5 Hz), self-excitation of header (header frame, header spindle, chopping cutter) and other working parts, which causes the coupled vibration of complex system. Through the comparison of modal parameters and vibration frequencies, it shows that the 2 order firing frequency of the engine produces a local mode of header, the road excitation will cause overall vibration, the vibration of header spindle and chopping cutter causes the one order bending mode shape, and the vibration of returning field machine causes the torsional mode. The result of this paper provides reference for vibration and modal measurement approach, offers guidance for design and optimization of header, and improves driving comfort level and working reliability.