Vibration Analysis And Structural Optimization Of Driving Platform For Crawler Combine Harvester

With the rapid development of agricultural mechanization in China, the demand for combine harvester grows gradually in recent years. By the advantage of high performance, lower prices and shorter payback period, the full-feed crawler combine harvester has become a mainstream model in this area. This kind of machine is only equipped with simple driving platform. And the designs of reducing vibration are rarely used. When the machine is working, the vibration occurred from working parts and ground can’t get effective damping. These would put a harmful effect upon the machine’s reliability and the driver’s working environment. With the maturity of the combine harvester technology, vibration and noise control of harvester is becoming more and more strict. The level of vibration and noise has become an important indicator to measure the quality of the products. Compared with foreign study, however, domestic studies of the vibration intensity as well as the whole anti-vibration performance of the combine harvester in the various operating conditions are still in its infancy. So the vibration and noise of combine harvester has become an urgent problem to be solved.In the paper, the crawler combine harvester CFFL-850 was chosen as experimental prototype to research the vibration characteristics of driving platform and the seat. The main contents include the following aspects:(1) The measurement of human body vibration and evaluation of the relevant standards were summarized, the evaluation standards and recommended limits which suitable combine harvester driver’s body were chosen with prototype structure and working environment and other factors, the test scheme of combine harvester driving was formulated in accordance with the selection criteria, the multiple operating mode of vibration was proceeded.(2) The frequency domain analysis, transmission characteristics and seat comfort evaluation were finished in accordance with the measured data from measuring points of this combine harvester. The main excitation source excitation frequency which caused the harvester vibration were obtained through frequency domain analysis. Through the comfort evaluation: the driving experience of the combine harvester were in extremely uncomfortable state under various conditions, condition 1 driving experience was the worst. The vibration on direction Z of the seat rotation influenced more than any other directions and measuring points. in human body vibration comfort. Through transfer characteristic analysis, it showed that: in the range are from1 to 50 Hz, the transmissibility coefficient of the seat almost were greater than 1, which indicated that in the sensitive frequency bands of the human body, the damping performance of seat was extremely bad, the seat structure, especially suspension system required to be improved.(3) Based on the theory of finite element analysis, the finite model of the driving hood was built by the software UG. The first 6th order modal frequencies and corresponding mode shapes were calculated by modal analysis. With the excitation system, DH5902 dynamic data acquisition system and modal analysis system, the laboratory modal testing about the combine harvester CFFL-850 driving hood was implemented. Comparing the modal test results and finite element analysis results, the accuracy of the driving hood finite element model were verified.(4) Finally, based on Sensitivity analysis, the independent variables of driving hood were selected, and the plan about structure optimization was established in order to adjust the hood natural frequencies to avoid the external excitation frequencies range. After solving in UG software and further modal analysis, the structure optimization parameters were finalized. It can be find that the first order natural frequency of optimized driving hood is raised to 15.46 Hz, the third order natural frequency is raised to 38.3 Hz. All modal frequencies are effectively avoided the harvester vibration frequency.(5) Due to the poor vibration reduction ability of the original seat, a new mechanical damping suspension structure was designed, which consists of hydraulic damper and mechanical springs. The new suspension structure was used on the original seat suspension system for the structure improvement. Then a vibration test was carried out to verify the result of the improvement. It showed that the seat vertical transfer coefficient were almost all below 1 under the conditions of walking on the road and harvesting in the field. The weighting acceleration root-mean-square values under the two conditions were reduced to 1.68 m/s2 and 1.46 m/s2, which was reduced by 28.5% and 42.9% respectively compared with before improvement. These illustrate the feasibility of improvement measures.