Study On Longitudinal Stability Of Wheeled Tractor Hanging Farm Implements Unit

In recent years,the demand for small and medium-sized wheeled tractors for hilly mountains is increasing.However,the terrain of hilly and mountainous areas is complex and diverse,irregular,uneven,and steep,which leads to more attention of wheeled tractors in the field.Safety.After the tractor hangs the implement,the center of gravity will change.When driving or farming,the safety accidents such as tipping and slipping are more likely to occur.Therefore,the crew must have good slope stability in hilly mountains.At present,most of the research on the stability of wheeled tractor units in hilly mountains is based on the theory that is not yet perfect,and the overall performance is often analyzed through repeated tests.Relying on the national key research and development project “Key Technology Research and Machine Development of Hilly Mountain Tractor”,the 26-horsepower wheeled tractor and its supporting rotary tiller unit produced by a company are taken as research objects,and the longitudinal stability of the unit is established based on theoretical mechanics.The model and the ADAMS virtual prototyping technology were used to carry out numerical simulation analysis of the longitudinal stability of the unit,and compared with the real vehicle experiment.The research work of this thesis provides a valuable theoretical basis and reference for the safe driving of the hillside tractors and the longitudinal stability design of the operation.The main research contents of this thesis are as follows:(1)Modeling of stability analysis of tractor unit.The static and dynamic longitudinal stability of the hilly wheeled tractor unit on the slope were analyzed by theoretical mechanics.The mathematical model of the longitudinal limit tumbling angle and slip angle of the static and dynamic longitudinal stability evaluation indexes of the unit was obtained for evaluation and Indicates the simulation results of the tractor unit stability.(2)Establishment of virtual model of tractor unit.The 3D modeling software SOLIDWORKS was used to create the engine,clutch,transmission,central drive,differential,final drive,frame,front steering axle,front and rear wheels,steering gear,hydraulic suspension system and rotary tiller for wheeled tractor units.The virtual model of the system assembly completes the assembly of the entire unit,and is imported into the ADAMS software to perform set-up and data processing on the material,mass,moment of inertia,Boolean operation and unit.(3)Numerical simulation and analysis of longitudinal stability of tractor unit.Based on the mathematical model of the longitudinal stability of the tractor unit and the virtual prototype,the ADAMS is used to simulate the motion of the unit,and the longitudinal stability of the unit in static and dynamic conditions is analyzed.Static analysis found that the limit tipping angle of the unit decreases first and then decreases with the decrease of the hanging height of the implement.The maximum tilt angle of the farm at 810 mm or 200 mm is the largest,and the slip angle decreases first and then increases with the increase of the suspension height.The maximum slip angle at 505mm;when the left rear wheel is suspended,the limit tilt angle of the unit is much lower than the limit tipping angle(25°)of the tractor unit in the hilly mountain.The unit is prone to tipping;dynamic analysis finds that the uniform uphill is possible.The limit tumbling angle and slip angle of the unit are less than the corresponding values at static time,and the influence law of the suspension height of the agricultural implement on the stability of the unit is consistent with the static time;the slip angle of the unit at a constant speed downhill is slightly smaller than that corresponding to the uniform uphill slope.The value,and the slip angle also decreases first and then increases with the increase of the suspension height,and is maximum at 505 mm;the limit tumbling angle of the unit when accelerating the uphill is smaller than the corresponding value at the uniform uphill,and the slant angle with the acceleration Increase and decrease.(4)Tractor unit stability real vehicle test.The static longitudinal stability tests of the units with three different heights of 810 mm,505mm and 200 mm were carried out,and the limit tumbling angle and slip angle of the unit were slightly larger than the simulation results.In addition,the ultimate tilt angle of the unit is 40.3°,36.4°,42.5° in three different positions,which meets the conditions of the extreme tilt angle(25°)of the tractor unit in the hilly mountain,and the slip angle is 24.5°,31.6°,25.4°,which also meets the limit slip angle of the tractor unit(11.3°);the influence law of the suspension height of the agricultural implement on the stability of the unit is consistent with the change of the simulation test results,which further proves the reliability of the virtual model and simulation results of the unit.And correctness;the uniform stability uphill stability test of the unit was carried out on an outdoor 15° slope road,and it was found that the unit did not tilt or slip during the climbing process,which is consistent with the theoretical analysis results.