TEMPERATURE PREDICTION OF DISPLACEMENT CONTROLLED MULTI-ACTUATOR MACHINES
Keywords:displacement control, excavator, heat transfer, thermodynamics
A promising technology for the advancement of fluid power systems is displacement controlled (DC) actuation. The main advantage of DC actuation is that metering losses are completely eliminated by replacing each actuator’s proportional valve with a variable displacement pump and controlling the actuator motion by pump displacement. This technology can achieve up to 50 % energy savings when compared to the conventional load sensing (LS) systems and the elimination of metering losses in DC systems is directly translated in lower heat generation. This paper presents a model to predict the thermodynamic behavior of multi-actuator displacement controlled machines. A complete mathematical model has been developed based on conservation of mass and energy. The model characteristics are discussed for an excavator, which contains four variable displacement pumps, three single-rod actuators, a rotary actuator for the slew, a gear pump, an accumulator, a heat exchanger, a reservoir, as well as metallic hydraulic lines and switching valves; however, the model has been created to be able to simulate not only the presented hydraulic circuit but different ones including those for larger off highway vehicles. Simulation results for measured working cycles of the excavator are presented and compared with measured temperatures of the machine. The simulation/measurement agreement demonstrates the validity and usefulness of the model.
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