機(jī)械專業(yè)外文翻譯－挖掘機(jī)的機(jī)械學(xué)和液壓學(xué)（英文）

1、 Proceedings of the 3rd International Modelica Conference, Linköping, November 3-4, 2003, Peter Fritzson (editor) Paper presented at the 3rd International Modelica Conference, November 3-4, 2003, Linköpin

2、gs Universitet, Linköping, Sweden, organized by The Modelica Association and Institutionen för datavetenskap, Linköpings universitet All papers of this conference can be downloaded from http://www.Modeli

3、ca.org/Conference2003/papers.shtml Program Committee ? Peter Fritzson, PELAB, Department of Computer and Information Science, Linköping University, Sweden (Chairman of the committee). ? Bernhard Bachmann, Fachhoc

4、hschule Bielefeld, Bielefeld, Germany. ? Hilding Elmqvist, Dynasim AB, Sweden. ? Martin Otter, Institute of Robotics and Mechatronics at DLR Research Center, Oberpfaffenhofen, Germany. ? Michael Tiller, Ford Motor Compa

5、ny, Dearborn, USA. ? Hubertus Tummescheit, UTRC, Hartford, USA, and PELAB, Department of Computer and Information Science, Linköping University, Sweden. Local Organization: Vadim Engelson (Chairman of local organiz

6、ation), Bodil Mattsson-Kihlström, Peter Fritzson. Peter Beater and Martin Otter Fachhochschule Südwestfalen in Soest; DLR, Germany: Multi-Domain Simulation: Mechanics and Hydraulics of an Excavator pp. 331

7、-340 Figure 1 Schematic drawing of excavator where the operator is sitting. It can rotate around a vertical axis with respect to the chain track. It also holds the Diesel engine, the hydraulic pumps and control system. F

8、urthermore, there is a boom, an arm and at the end a bucket which is attached via a planar kinematic loop to the arm. Boom, arm and bucket can be rotated by the appropriate cylinders. Figure 2 shows that the required pre

9、ssures in the cylinders depend on the position. For the “stretched” situation the pressure in the boom cyl- inder is 60 % higher than in the retracted position. Not only the position but also the movements have to be tak

10、en into account. Figure 3 shows a situation where the arm hangs down. If the carriage does not rotate there is a pulling force required in the cylin- der. When rotating – excavators can typically ro- tate with up to 12 r

11、evolutions per minute – the force in the arm cylinder changes its sign and now a pushing force is needed. This change is very sig- nificant because now the “active” chamber of the cylinder switches and that must be taken

12、 into ac- count by the control system. Both figures demon- strate that a simulation model must take into ac- count the couplings between the four degrees of freedom this excavator has. A simpler model that uses a constan

13、t load for each cylinder and the swivel drive leads to erroneous results (Jansson et al. 1998).Figure 2 Different working situationsFigure 3 Effect of centrifugal forces4. Load Sensing SystemExcavators have typically one

14、 Diesel engine, two hydraulic motors and three cylinders. There exist different hydraulic circuits to provide the consum- ers with the required hydraulic energy. A typical design is a Load Sensing circuit that is energy

15、effi- cient and user friendly. The idea is to have a flow rate control system for the pump such that it deliv- ers exactly the needed flow rate. As a sensor the pressure drop across an orifice is used. The refer- ence va

16、lue is the resistance of the orifice. A sche- matic drawing is shown in figure 4, a good intro- duction to that topic is given in (anon. 1992). The pump control valve maintains a pressure at the pump port that is typical

17、ly 15 bar higher than the pressure in the LS line (= Load Sensing line). If the directional valve is closed the pump has there- fore a stand-by pressure of 15 bar. If it is open the pump delivers a flow rate that leads t

18、o a pressure drop of 15 bar across that directional valve. Note: The directional valve is not used to throttle the pump flow but as a flow meter (pressure drop that is fed back) and as a reference (resistance). The circu

19、it is energy efficient because the pump deliv- ers only the needed flow rate, the throttling losses are small compared to other circuits. If more than one cylinder is used the circuit becomes more complicated, see figure

20、 5. E.g. if the boom requires a pressure of 100 bar and the bucket a pressure of 300 bar the pump pressure must be above 300 bar which would cause an unwantedFigure 4 Schematics of a simple LS system (Zähe)Peter Bea

21、ter and Martin Otter Multi-Domain Simulation: Mechanics and Hydraulics of an Excavator The Modelica Association