| Wheeled excavator has the advantages of strong mobility and fast transition speed,which plays an irreplaceable role in civil and military construction.The further improvement of the speed of the whole machine has great practical significance for military and civil.However,the high-speed running of the whole machine will inevitably lead to the further amplification of the road input excitation.Nowadays,the comfort measures of the wheel excavator are only the cab and seat suspension,and there is no suspension between the axles to reduce the vibration.This is acceptable when the whole machine is running at low speed.When the speed exceeds 50km/h,the suspension system must be introduced to reduce the excessive road vibration.A few wheel excavators use leaf spring suspension,and its stiffness is fixed,which does not meet the needs of high-speed wheel excavators for suspension.The stiffness requirements of suspension are not the same in the process of highspeed walking and operation.Small stiffness and damping can provide comfort for high-speed walking of excavator,but it will make the vehicle turn sharply or in the process of operation,The change range of body posture is too large.Large suspension stiffness and damping can ensure the body height of the excavator is basically constant during operation,but it can not fully dissipate the road excitation at high speed,thus affecting its ride comfort.Therefore,the suspension stiffness and damping properties that meet the requirements of high-speed wheeled excavators should be variable.Hydro pneumatic suspension is an ideal type of suspension.It uses compressed nitrogen as the elastic element to support the body.Its stiffness is variable and increases sharply with the increase of compression degree.It has the advantages of small volume,light weight and strong bearing capacity.It can well meet the needs of wheel excavator for suspension.In this paper,the single chamber oil and gas suspension is chosen as the introduction type of high-speed wheel excavator.On the individual level of research,the mathematical expression model of oil and gas suspension is established.The accuracy of the above model is proved by the dynamic and static test of the oil-gas suspension cylinder.On the basis of the model,the influence of the parameters on the stiffness and damping characteristics of the oil-gas suspension cylinder is studied by simulation;Then,the smooth performance of the whole machine is evaluated from the system level.The vibration model of wheel excavator two degree of freedom suspension system is established.The expression model of road input is established according to relevant standards,including impact excitation and random road excitation.Finally,in AMESim,the simulation model of wheel excavator secondary self-reliance suspension system with leaf spring suspension and oil-gas suspension is established respectively,and the performance of the two is evaluated and compared,The results show that compared with the leaf spring suspension,the oil-gas suspension has been improved greatly in three evaluation indexes.Because all the structural parameters of hydro pneumatic suspension will affect its external characteristics,it is necessary to optimize it to make hydro pneumatic suspension present better stiffness and damping characteristics.In this paper,the genetic optimization algorithm is used to establish the corresponding optimization model.The results show that under the same working conditions,the performance indexes of the optimized hydro pneumatic suspension are improved compared with those before optimization,The minimum center of mass acceleration,suspension dynamic deflection and wheel dynamic load are increased by 22.3%,23.0% and 0.62% respectively. |
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