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2020.2 Release Notes – Hydraulics Library 4.14

Hydraulics Library v4.14 is part of Modelon’s 2020.2 release.

New versions of Modelon libraries are sold and distributed directly from Modelon, as well as approved resellers.


  • The interfaces have been reworked in order to better highlight the expected connections to each port. This affects every hydraulic component.
    • Three port types are now available:
      • The flow port should be connected to volume ports only for efficient modeling.
      • There should be one and only one volume port per node for efficient modeling.
      • The neutral port is less constrained in terms of connection but some local rules might apply and would be detailed in components’ help.
    • There is no more visual distinction on the port icon between what was a port_A and port_B previously, as this was reported to be more confusing than helpful. In two ports components, an arrow is added to highlight the positive direction of the flow.
    • Port icons have been adapted to fit the visual aspect of other Modelon libraries.
    • Previous Port_A and Port_B are now deprecated
  • Cavitation of the fluid is now properly modeled in VolumeDynamics. This includes:
    • when reaching vapor pressure, the oil starts to become gaseous,
    • the fraction of gaseous oil is tracked and oil pressure cannot raise (with incoming flow) unless the entire gaseous oil volume is transformed back into liquid oil.
    • The gaseous fraction of the oil volume is local to the volume and not transferred through ports. Mass flow exiting the volume is always liquid oil.
    • Warnings are raised if the entire volume of oil becomes gaseous, as the physics would not be ensured.
  • A single-acting cylinder with feedback spring is added to the library.
  • Command logic now have a minimum value of the flow and an outflow enthalpy set to zero, as well as state selection avoided. This simplifies mixing computations in case of non-optimal port connection.
  • Visualizers now have state selection set to avoid pressure variables.

Fixed Issues

  • Resolved array size mismatch in TwoPortFlexible, SpoolGeneric_4_X_X, DCV_4_2_X and DCV_4_3_X.
  • Updated PilotCheckValveCircuit to use an elastic friction model for better robustness
  • Propagated initialization parameters related to volumes in several components, especially in the DirectionalControl and Valves packages access these more conveniently.
  • Restrictions in Plunger and Differential cylinders were connected so that an external leakage from the chambers to the environment would be negative. For convenience only, these restrictions have been flipped to have a positive leakage flow when going from the chambers to the environment.

New classes

  • Interfaces.FlowPort
  • Interfaces.VolumePort
  • Interfaces.NeutralPort
  • Lines.Basic.Templates.TwoPort
  • Cylinders.SingleActingCylinder
  • Cylinders.Templates.SingleActingCylinder
  • Cylinders.Interfaces.SingleActingCylinder

Moved classes

  • RotaryActuators.ConstantFlowPump –> Hydraulics.Examples.PowerSteering.Components.ConstantFlowPump

Obsolete classes

Obsolete classes are placed in the package Utilities. Deprecated and will be removed after a year from the release when they were put in the deprecated package.

  • Utilities.Deprecated.Port_A
  • Utilities.Deprecated.Port_B
  • Utilities.Deprecated.FourPort

Conversion of user libraries

Automatic conversion of user libraries from version 4.13 to 4.14 is partially supported using the included conversion script “Convert_to_4.14.mos” located under Hydraulics 4.14\Resources\Scripts.


Hydraulics 4.14 is based on Modelon Base Library 3.6 and Modelica Standard Library 3.2.3.

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