挖掘機(jī)-外文翻譯-外文文獻(xiàn)中英翻譯(文件)
【正文】 d sense valve pressure and the diference of pressure, respectively. The pressure experiment curves of the system show the variation of three kinds of pressures．Although Ps and pls change with load，their difference does not change with load，the value approximates to ，the effect of on the flow across the valve can be neglected．It is assumed that the flow across the valve is proportional to the size of orifice valve，and the flow is not influenced by load．Then，Eqn．(2) can be simplified as Q1=Kqxv(t),I(t)≥0 (4)where is the flow gain coefficient of valve, m2／s, and Curves of pressure experiment under boom moving condition Continuity equation of hydraulic cylinder Generally speaking，construction machine does not permit external leakage．At present，the external leakage can be controlled by sealing technology．On the other hand，it has been proven that the internal leakage of excavator is quite little by experiments．So, the influence of internal and external leakage of hydraulic system can be ignored．When the oil flows into head side of cylinder and discharges from rod side， the continuity equation can be written as (5)where V1 and V2 are the volumes of fluid flowing into and out the hydraulic cylinder, m3 ； is the effective bulk modulus(including liquid，air in oil and so on)，N/m2． Force equilibrium equation of hydraulic cylinder It is assumed that the mass of oil in hydraulic cylinder is negligible,and the load is rigid. Then the force equilibrium equation of hydraulic cylinder can be calculated from the Newton’s second law： (6)where Bc is the viscous damping coefficient，Na0=V1V2m。 is the length from point O1 to point B．According to the rotating law：M=J,we get that is （9） where J is the equivalent moment inertia of manipulator to point O1,kgm.Comparing Eqn．(9)with Fc=mac，the equivalent mass at point B can be given： (11) Estimation for load on hydraulic cylinderThe equivalent moment equation of manipulator to O1 is (12)where and are the length from pointO1 to point G1180。A)． Flow of boom cylinder under electrohydeaulic proportional value controlled by step current5 Conclusions（1）The mathematic model of electro—hydraulic system is developed according to the characteristics of excavator．It is assumed that the flow across the valve is directly proportional to the size of valve orifice，and the influence of intemal and extemal leakage of hydraulic system is ignored．The simplified model can be obtained：where represent the displacement of piston and the displacement of spool．（2）From the model of electro—hydraulic system，we can obtain the equivalent mass ，bearing force , flow gain coefficient of value KqKl=104m3/(sand G3180。m, J2=.4 Parameters estimationFrom the process of modeling and Eqn．(7)，it is clear that all parameters in the simplified model are related to the structure。are projections of Gl，G2 and G3 on x axis，respectively． The arm of excavator was considered a manipulator with three degrees of freedom (three inclinometers were set on the boom，dipper and bu
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