| Hydraulic excavator is one of the main types of the earth-movingmachinery,plays a very important role in the program of Engineering constraction anddevelopment of land.The specialization is one of the development trends of hydraulicexcavator,it can effectively ensure the excavator finish the tsak efficiently in aparticular environment.The working device is the actuator of excavator,its performance would directlydetermine the capability of the whole machine. Since the excavator would always facethe load vary within wide limits, careful work and a series of complex workingconditions,therefore there is a high requirement of the hydraulic system of theworking device. So the research on the performance of the hydraulic system of theworking device is of an important practical significance.The previous research on thehydraulic system of the working device was mostly based on the mathematical model,which took a variety of simplification and equivalence to the components and the load,and couldn’t reflect the dynamic characteristics of hydraulic system accurately.Considering this matter, this thesis combines with the project of "2DOF ArticulatedWheeled-off road excavator development", takes the hydraulic system of the workingdevice of as studying object, and adopts AMESim simulation software to simulate andanalyze the dynamic characteristics of the hydraulic system.This paper focuses on the following aspects of work,introduces the specializationcharactristics of the prototype,the development situation and trends of the excavatorhydraulic system in domestic and foreign,illustrates the basic compositions of theexcavator and puts forwards the design requirements of the hydraulic systemcombined with the actual working condition,and the excavator digging force and thework scope are calculated and analyzed.Studies the two hydraulic systems of opencenter system and closed center system. Analyses the principle of full power control，devided power control,alternate power control.Deduces the static and dynamicmathematical model of alternate power-negative flow control system and analysisthe parameters affect the variable pump’s discharge. Based on the principle diagramof the prototype working device hydraulic system,the principle of alternate power-negative flow control system, the variable pump power curve and so on. Builds theAMESim simulation model of the pump control system,the valve control system, theworking device, the rotary system on the AMESim platform. Under no-loadcondition,simulates the arm, boom, bucket,rotary loop respectively in seperatelyactions. The simulation results show: the highly rotary speed of working device cause a great hydraulic impact.At the same time, founding bucket hydraulic cylinder strokeis too large, and the boom and the bucket always collision each other. The correctnessof the simulation model is verified through the experimental study on the hydraulicsystem of the prototype working device,and the dynamic characteristics of the systemis analyzed.The results can provide a certain reference for the prototype furtherimprovements and meet production research worker later. |
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