液压挖掘机.docx

1、液压挖掘机Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering) ISSN 1673-565X (Print); ISSN 1862-1775 (Online) E-mail: jzusQuantitative measures for assessment of the hydraulic excavator digging efficiency*Dragoslav JANOSEVIC1, Rosen MITREV2, Boban ANDJELKOVIC1, Plamen PETROV2(1Facult

2、y of Mechanical Engineering, University of Nis, Nis 18000, Serbia) (2Faculty of Mechanical Engineering, Technical University of Sofia, Sofia, Bulgaria)E-mail: janosmasfak.ni.ac.rsReceived Nov. 18, 2011; Revision accepted Mar. 27, 2012; Crosschecked Nov. 1, 2012Abstract: In this paper, quantitative m

3、easures for the assessment of the hydraulic excavator digging efficiency are proposed and developed. The following factors are considered: (a) boundary digging forces allowed for by the stability of an excavator, (b) boundary digging forces enabled by the driving mechanisms of the excavator, (c) fac

4、tors taking into consideration the digging position in the working range of an excavator, and (d) sign and direction of potential digging resistive force. A corrected digging force is defined and a mathematical model of kinematic chain and drive mechanisms of a five-member excavator configuration wa

5、s developed comprising: an undercarriage, a rotational platform and an attachment with boom, stick, and bucket. On the basis of the mathematical model of the excavator, software was developed for computation and detailed analysis of the digging forces in the entire workspace of the excavator. By usi

6、ng the developed software, the analysis of boundary digging forces is conducted and the corrected digging force is determined for two models of hydraulic excavators of the same mass (around 17 000 kg) with identical kinematic chain parameters but with different parameters of manipulator driving mech

7、anisms. The results of the analy- sis show that the proposed set of quantitative measures can be used for assessment of the digging efficiency of existing excava- tor models and to serve as an optimization criterion in the synthesis of manipulator driving mechanisms of new excavator models.Key words

8、: Hydraulic excavators, Digging efficiency, Quantitative measuresdoi:10.1631/jzus.A1100318 Document code: A CLC number: TV531 IntroductionThe hydraulic excavators are popular multifunc- tional construction and mining machines. The main function of the hydraulic excavators of all types and sizes is t

9、he cyclic digging and transfer of soil. This function is achieved by use of an open kinematic chain consisting of undercarriage L1, an upper struc- ture L2 and a front attachment with boom L3, stick L4 and work tool L5 (Fig. 1). For digging operations below the ground level, the toward oneself techn

10、ol- ogy (in relation to the excavator operator) is em- ployed and a backhoe attachment is used (Fig. 1a).* Project (No. 035049) partly supported by the Ministry of Education and Science of the Republic of Serbia Zhejiang University and Springer-Verlag Berlin Heidelberg 2012For digging operations abo

11、ve the ground level the away from oneself technology and a shovel attach- ment are used (Fig. 1b).During digging operations, the occurring dig- ging resistive force acting against the manipulator tool is overcome by digging forces. The digging forces of an excavator are exerted by the kinematic chai

12、n of the excavator, which is powered by the fol- lowing driving mechanisms: (1) hydraulic motors for motion of swing and travelling bodies; (2) double acting hydraulic cylinders for powering of the ma- nipulator links.For an optimal design of the front manipulator and driving mechanisms, it is neces

13、sary to perform a detailed analysis of the digging forces and the digging resistive forces in the entire workspace of the excava- tor. The conducted analytical and experimentalresearch that points out the importance of knowledge about the digging resistive forces for development and analysis of hydr

14、aulic excavators is related to: (1) analytical modeling and experimental determination of the value and the change in the digging resistive force during the excavation process (Maciejewski and Jarzebowski, 2002; Maciejewski et al., 2003; Yang et al., 2008); (2) development of mathematical models for

15、 kinematic and dynamic analysis of exca- vators (Budny et al., 2003; Towarek, 2003; Hall and McAree, 2005; Gu et al., 2007); (3) development of control systems for automation of the digging proc- ess (Plonecki et al., 1998; Ha et al., 2000; Chang and Lee, 2002; Lee and Chang, 2002; Flores et al., 20

16、07; Lin et al., 2008); and, (4) definition of quantitative measures for analysis and assessment of excavator digging efficiency in the workspace.LL32L4L5L1 (a)L3L2L4L5L1(b)Fig. 1 Hydraulic excavators with backhoe (a) and shovel attachment (b)As indicated by the manufacturer, stick and bucket digging

17、 forces are important parameters of the excavator. They are defined by appropriate stan- dards (ISO 6015, 2006; SAE J1179, 2008) as one of the characteristics of the excavator digging function. For robotic manipulators, quantitative measures of workspace attributes are defined, which includes struct

18、ural length index and manipulability measure(Craig, 2005). Some of these measures can be used for the assessment of the dynamic performance of shovels (Lipsett, 2009). In many cases, the above mentioned measures are not sufficient for assessment of digging possibilities and efficiency of the excava-

19、 tor in the workspace.In this paper, a set of quantitative measures for assessment of the hydraulic excavator digging effi- ciency is proposed and developed.For a comprehensive analysis of values and di- rections of digging forces in a specific position of the front manipulator, a hodograph of bound

20、ary digging forces at the top of the bucket tooth is defined. It has a form of a polygon whose sides are composed by vectors of boundary forces exerted by the manipula- tor driving mechanisms and vectors of boundary forces allowed by the stability of the excavator. The ratio of the computed digging

21、force and the potential digging force is defined as a measure of the digging efficiency. The computed digging force is deter- mined by a mathematical model of the excavator. Computations are performed for a given position and orientation of the manipulator and pressures in the hydraulic cylinders of

22、 driving mechanisms. The po- tential digging force represents the minimum value of boundary digging forces (Dudczak, 1977).A hodograph of the effective digging forces is defined as a part of the hodograph of the boundary digging forces, for which the dot product of the dig- ging velocity and digging

23、 force vector is positive. The ratio of the area and range of the effective dig- ging forces hodograph is accepted as a criterion for excavator digging efficiency, whereas the area of the effective hodograph represents the mean value of the allowed digging forces. The range of the hodograph of the e

24、ffective digging forces reflects the degree of compatibility of manipulator actuator parameters, excavator weight distribution, and digging force dis- tribution (Budny, 1989).A corrected digging force is set as a measure of digging efficiency in the entire workspace. The fol- lowing considerations a

25、re taken into account: bound- ary digging forces allowed by the stability of an ex- cavator; boundary forces exerted by the driving mechanisms of an excavator; and factors which re- late to the digging position of the manipulator in the workspace as well as the sign and direction of the potential di

26、gging resistance action (Janosevic, 1997).In this paper, mathematical models of the exca- vator kinematic chain, driving mechanisms and boundary digging forces are proposed and developed.2 Mathematical modeling of excavatorA side view of the excavator is shown in Fig. 2. The mathematical model of th

27、e excavator consists of the mathematical model of the excavator kine- matic chain and that of the manipulator driving mechanisms.2.1 Model of the excavator kinematic chainThe excavator represents a five-link open kine- matic chain which consists of the travelling body L1, the swing body (rotational

28、platform) L2 and the three-link front manipulator consisting of a boom L3, a stick L4, and a bucket L5 (Fig. 2).The links of the front attachment kinematic chain are connected by kinematic pairs of the fifth classrotational joints with a 1 DOF with different orientations in the space. The kinematic

29、chain of the front manipulator which is a part of the excavator model is planar. The centers of the manipulator joints Oi (i=3, 4, 5) are penetration points of joint axis through the plane of symmetry of manipulator chaintor is considered as an open kinematic chain with a last link (bucket) that is

30、subjected to the digging re- sistive force W (Janosevic, 1997).To describe mathematically the kinematic model of the excavator, the following coordinate systems have been assigned:(1) Global reference frame OXYZ with unit vectors i, j, k along the coordinate axes OX, OY, and OZ, respectively. The su

31、pport base lies in the hori- zontal plane OXZ and the vertical axis OY coincides with the axis of the rotational joint between the un- dercarriage and upperstructure O2.(2) Body fixed coordinate systems Oixiyizi (i=1,2, 3, 4, 5), which are connected to each link Li of the kinematic chain. The coordi

32、nate systems beginning Oi is situated in the center of joint by which the chain member Li is connected to the previous member Li1. The bucket is connected to a coordinate system whose axis O5x5 passes through the center of the joint O5 and the top of the cutting edge of the bucket Ow.In the case of the stationary undercarriage, the coordinate system O1x1y1z1 coincides with the global coordinate system.The geometry of the kinematic chain links Li is defined in its local coordinate