Simulation Analysis On Vibration Comfort And Structural Optimization Of The Combine Harvester

Working environment of the combine harvester is complex and the combine harvester bears much vibration excitation.This condition easily leads to the driver's discomfort.When the external excitation resonates with the harvester body,the discomfort is particularly intense.Working in the circumstance for a long time not only leads to driver's fatigue,but also causes nerve injury and spinal cord injury problems.Therefore,it is necessary to comprehensively consider the influence of the working environment and vibration excitation on the vibration comfort of the harvester,and improve the structure of the harvester to increase its vibration comfort and reliability.A certain combine harvester was taken as the research object in this study.The integrated using of mechanical vibration theory and multi-body system dynamics theory and combining the Solidworks,HyperMesh,ANSYS and RecurDyn software,the dynamic model of the rigid-flexible coupling multi-body of the man-machine-pavement system was established creatively,and the vibration characteristics of the harvester were simulated and analyzed.Then,the dynamic signal analyzer was used to test the vibration of the harvester,and the test results were compared with the simulation results to verify the virtual prototype model of the system.Based on this,the vibration comfort of the harvester was simulated and calculated.Finally,the model analysis and calculation of the body of the harvester have been carried out by using the HyperMesh software,and based on the result of model analysis,the vehicle body frame thickness is optimized to improve the natural frequency of the first stage of the body of the harvester so as to avoid resonance of the vehicle body and the related excitation.The main research contents and conclusions are as follows:Firstly,a new type of rigid flexible coupling model was established.Using Solidworks and Track LM module of RecurDyn software to create the main body of the harvester and crawler walking structure of the rigid body model,and they were combined to create a rigid model of the harvester;HyperMesh software was used to build the harvester body flexible body,ANSYS was used to process the flexible body then used the RecurDyn software modal flexible body module,and combined it with the rigid model to build the hybrid model of rigid flexible coupling harvester.Secondly,The rigid-flexible virtual prototype model of man-machine-pavement system of the combine harvest was established creatively.According to the national standard GB 10000-88 Chinese Adult Body Size and GB/T 17245-2004 Adult Human Inertia Parameter,Geometric model of human body in driver sitting by using Solidworks software.According to the national standard GB 7031-86 Measurement of Vibration Input-Road Flatness Representation Method and ISO / DIS 8608 Mechanical Vibration-Road Profile-Measurement Data Reporting Method,the harmonic superposition was used to prepare the road spectrum file,and the road surface excitation model was established.Based on the RecurDyn software platform,the rigid and flexible coupling model of the harvester was combined with the human body model and the road surface excitation model.According to the motion relationship among the components of the harvester,the rigid and flexible coupling prototype model of the man-machine-pavement system of the harvester was established by applying constraints and driving.And the vibration characteristics of the harvester were simulated and analyzed on the basis.The dynamic signal analyzer was used to test the vibration of the harvester,and the test results were compared with the simulation results to verify the virtual prototype model of the system.Thirdly,when the combine harvester was operating,the vibration comfort of the driver was analyzed and evaluated by simulation analysis and experimental study.Based on the model of rigid-flexible coupling virtual model of man-machine-pavement system of the harvester,and referred to the national standard GB/T10910-2004 Agricultural Wheeled Tractors and Field Machinery and Measurement of Whole Body Vibration of the Operator and GB/T13876-2007 Agricultural Wheeled Tractors of Whole Body Vibration of the Operator Evaluation Index,the vibration comfort of the harvester driver was simulated and evaluated in different driving speed and road surface motive conditions so as to explore the influence of the driving speed and the road surface roughness on it.The vibration comfort of the harvester was analyzed and evaluated by the dynamic signal analyzer.The results were compared with the simulation analysis.It was found that the vibration test and the simulation result of the harvester were in good agreement,it meant that the established man-machine-pavement system rigid-flexible coupling virtual prototype model is effective and its accuracy basically satisfies the receiver vibration comfort analysis requirements.Fourthly,The results of comprehensive vibration test and simulation showed that the vibration comfort of the harvester was very poor when the harvesting machine was in operation.The driving speed and the road surface roughness have a great influence on the vibration comfort of the harvester.When driving in high speed,the driver's vertical vibration intensity was significantly higher than the lower vehicle speed vibration intensity.In the large road on the road driving,the driver's subjective vibration was significantly stronger than the soft road vibration.When driving in hard road,the subjective vibration the driver was significantly stronger than the soft road.By analysis the vibration signal power spectral density,it can be found that the seat bearing surface longitudinal(X axis)vibration peak frequency is about 14 Hz,and horizontal(Y axis)and vertical(Z axis)vibration peak frequency is about 7Hz,which showed that the vibration energy delivered to the driver's body was mainly derived from the cutter and the threshing drum.Fifthly,size optimization and topology optimization technology were used to optimize the body structure of the combine harvester.Using HyperMesh software to carry on the modal analysis and calculation to the body of the harvesting machine,it was found that the first frequency of the body of 7.29 Hz was close to the cutter excitation frequency(7Hz),so it caused resonance easily.To avoid resonance,OptiStruct size optimization and topology optimization technology was applied to optimize the thickness of the body frame.After size optimization the first-order mode frequency of the body was enhanced to 8.63 Hz,while the quality of the body was reduced 0.006 t.After topology optimization the first-order mode frequency of the body was enhanced to 8.49 Hz,while the quality of the body was reduced 0.107 t.