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1、重庆交通大学二OO九届毕业设计（论文）译文外文原文：Modeling and parameter estimation for hydraulic system of excavators armHE Qing-hua，HAO Peng，ZHANG Da-qingAbstractA retrofitted electro-hydraulic proportional system for hydraulic excavator was introduced firstly. According to the principle and characteristic of load indepe
2、ndent flow distribution (LUDV) system, taking boom hydraulic system as an example and ignoring the leakage of hydraulic cylinder and the mass of oil in it ,a force equilibrium equation and a continuous equation of hydraulic cylinder were set up. Based on the flow equation of electro-hydraulic propor
3、tional valve, the pressure passing through the valve and the difference pressure were tested and analyzed. The results show that the difference of pressure does not change with load and it approximates to 2.0MPa. And then, assume the flow across the valve id directly proportional to spool displaceme
4、nt and is not influenced by load, a simplified model of electro-hydraulic system was put forward. At the same time, by analyzing the structure and load-bearing of boom instrument, and combining moment equivalent equation of manipulator with rotating law, the estimation methods and equations for such
5、 parameters as equivalent mass and bearing force of hydraulic- cylinder were set up. Finally, the step response of flow of boom cylinder was tested when the electro-hydraulic proportional valve was controlled by the step current. Based on the experiment curve, the flow gain coefficient of valve unid
6、entified as 2.82510-4m3/(sA) and the mode is verified.Key words: Excavator, Hydraulic-cylinder proportional system, Load independent flow distribution (LUDV) system, Modeling, Parameter estimation1 IntroductionFor its high efficiency and multifunction, hydraulic excavator is widely used in mines，roa
7、d building, civil and military construction，and hazardous waste cleanup areasThe hydraulic excavator also plays an important role in construction machinesNowadays, macaronis and mobilization have been the latest trend for the construction machinesSo，the automatic excavator gradually becomes popular
8、in many countries and is considered a focusMany control methods can be used to automatically control the manipulator of excavatorWhichever method is used, the researchers must know the structure of manipulator and the dynamic and static characteristics of hydraulic systemThat is, the exact mathemati
9、cal models are helpful to design controller However, it is difficult to model on time-variable parameters in mechanical structures and various nonlinearities in hydraulic actuators， and disturbance from outsideResearches on time delay control for excavator were carried out in RefsNGUYE used fuzzy sl
10、iding mode control and impedance control to automate the motion of excavators manipulator SHAHRAM et al adopted impedance control to the teleported excavatorNonlinear models of hydraulic system were developed by some researchers. However, it is complicated and expensive to design controller, which 1
11、imits its applicationIn this paper, based on the proposed model，the model of boom hydraulic system of excavator was simplified according to engineering and by considering the force equilibrium， continuous equation of hydraulic cylinder and flow equation of electro-hydraulic proportional valve；at the
12、 same time，the estimation methods and equations for the parameters of model were developed2 Overview of robotic excavatorThe backhoe hydraulic excavator studied is shown in Fig.1In Fig.1，Fc presents the resultant force of hydraulic cylinder, gravity of boom，dipper, bucket and so on at point B，whose
13、direction is along cylinder AB； Fc can be decomposed into Fcl and Fc2，and their directions are vertical and parallel to that of O1B，respectively；ac is the acceleration whose direction is same to that of Fc，and ac can be decomposed into acl an d ac2 too；G1，G2 and G3 are the gravity centers of boom，di
14、pper and bucket，respectively；ml，m2 and m3 are the masses of them，and their values can be given by experiment( m1=868.136kg，m2=357.115kg and m3=210.736kg)；Ol，O2 and O3 are the hinged points；G1，G2and G3are projections of Gl，G2 and G3 on x axis，respectively The arm of excavator was considered a manipul
15、ator with three degrees of freedom (three inclinometers were set on the boom，dipper and bucket，respectively)In tracking control experiment，the objective trajectories were planed based on the kinematic equation of excavators manipulatorThen，the motion of boom，dipper an d bucket was set by the control
16、lerIn order to suit for automatic contro1the normal hydraulic control excavator should be retrofitted to electro-hydraulic controllerBased on original hydraulic system of SW E-85The hydraulic pilot control system was replaced by an electro-hydraulic pilot control systemThe retrofitted hydraulic system is shown in Fig.2In this work，because boom，dipper an d bucket are of the same characteristics，the hydraulic system of boom was taken a
