Design Of Tractor Cab's Air-suspension System And Research On The Whole Machine Simulation Test

With the development of agricultural machinery and agricultural economy,people have an increasing higher demand on driving comfort.However,the suspension structure of tractors,develops slowly,and can't meet driver's comfort requirements.The poor conditions where tractors work in and the design defects of machines always make engineering vehicles generate high-intensity low-frequency vibration which impact driver's physical and mental health seriously.So,it's necessary to reduce the vibration of tractors.Compared with other damping measures,improving the cab suspension is a direct way.Therefore,there is a great significance to research the dynamic characteristics of tractor cab suspension system for improving the driving comfort.This project is aimed at reducing the cab vibration intensity and its influence on driver's health and improving driving comfort.Taken the CF700 tractor as an example,the difference equation of motion was list according to the Newton's second law;A new full floating cab suspension system which took air spring as the elastic damping elements was designed;The dynamic tractor model was built and the cab parameters were simulated in ADAMS;The finished work and achieved results are generalized as follows:(1)The four degrees of freedom plane model was built according to the structure and vibration characteristics of the CF700 tractor,the difference equation of motion was list and the cab's equivalent stiffness in vertical direction and nature frequency were derived based on simplified model;The air spring's vibration frequency was derived from its mechanical model;The influence factors which would influent tractor vibration characteristics were researched and the results showed that those factors included tractor mass,tire properties,road excitation,driving speed and suspension parameters.(2)The three degrees of freedom cab suspension system made up by air spring shock absorber,guide mechanism and some connectors was designed.The air spring shock absorber was selected according to the suspension load,installation dimension and suspension travel The air spring's out-put force and dynamic characteristics was researched and analyzed by bench test.To select the accurate rubber bushing,horizontal rod and vertical rod were analyzed with the finite element method.The strength of the bolts with large load in guide mechanism was checked.(3)According to national standards,the rough road files used in simulation were prepared;Tire files were also prepared based on tire parameters;Cab dynamic model was built using the air spring test data,and obtained the appropriate suspension parameters by simulation.The whole tractor model was built in Pro/E,and was imported into ADAMS to be a virtual prototype model with setting the material properties,constraint conditions and load conditions.(4)The time-domain signal of vibration in X,Y,Z directions and acceleration of cab seat was obtained by field test in two conditions;The root-mean-square(RMS)of acceleration in three directions acquired in test was compared with the simulation result in ADAMS,and the virtual prototype model was checked;The vibration characters of the cab centroid was researched in ADAMS.The project is aimed at researching the dynamic characteristics of tractor cab about the relationship between vibration characteristics and driving speed,suspension parameters and spectrum peak frequency,and providing researching foundation for reducing tractor vibration intensity.