Abstract
In hydraulic components, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for numerical simulation. With particular reference to hydraulic spool valves, the viscous friction coefficient between the sliding and the fixed body is an unknown parameter that is normally set a posteriori in order to obtain a good agreement with the experimental data. In this paper, two different methodologies to characterize experimentally the viscous friction coefficient in a hydraulic component with spool are presented. The two approaches are significantly different and are both based on experimental tests; they were developed in two distinct laboratories in different periods of time and applied to the same flow compensator of a pump displacement control. One of the procedures was carried out at the Fluid Power Research Laboratory of the Politecnico di Torino, while the other approach was developed at the University of Parma. Both the proposed methods reached similar outcomes; moreover, neither method requires the installation of a spool displacement transducer that can significantly affect the results.
Highlights
In the lumped parameter modelling of fluid power components, some coefficients that play a critical role in the simulation are typically unknown and not easy to be determined or to be found in the open literature
In hydraulic systems, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for the numerical simulation
To analyze analyze the the effects effects of of the the presence presence of of aa linear linear variable variable displacement displacement transducer transducer (LVDT), (LVDT), further further tests tests were werecarried carriedout outat atthe the Figure reports the mounted on the component
Summary
In the lumped parameter modelling of fluid power components, some coefficients that play a critical role in the simulation are typically unknown and not easy to be determined or to be found in the open literature. The unknown parameters of a complex simulation model of an entire hydraulic system are selected a posteriori in order to obtain a good agreement with a few available experimental data. With this approach, the predictive capability of the model could be compromised, and its reliability in evaluating quantitatively the influence on the system performance of a parameter modification could be questionable, especially if the number of the unknown coefficients is high. In order to avoid this limitation, the best procedure, when possible, is to characterize as best as possible the single components with focused tests In this way, the reliability of the system-level model can be improved
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