DoubleRodCylinder

Library

HydraulicsByFluidon/Components/Cylinders

Description

Model of a double rod cylinder with Stribeck friction and volumetric losses.

The fundamental geometrical properties of the double rod cylinder are the piston and rod diameters (pistonDiameter, rodDiameterA, rodDiameterB) as well as the lengths of the cylinder and the rod (cylinderLength and rodLength). By using the parameter angle, the inclination of the cylinder with respect to the horizon can be adjusted. The resulting forces due to gravity are taken into account automatically, however without inclusion of static fluid masses.

For dynamic calculations, the masses of the piston and the cylinder are required. These can be provided by specifying the parameters Piston mass and Cylinder mass. The dynamic mass of the fluid, which acts as an additional inertia, is automatically taken into account by the model.

The parameters Breakaway friction force, Constant friction/Coulomb force, Velocity dependent friction and Velocity parameter for Stribeck friction (velocity where the friction force begins to grow linearly) characterize the velocity dependence of the friction force between piston and cylinder. Instead of using the Stribeck friction model, a simplified friction calculation can be enabled by setting the check mark relFric. In this case, the friction force equals the net force acting on the interface between piston and cylinder multiplied by the parameter Relative friction factor. Regardless of which friction model is used, the friction force is not influenced by the inclination of the cylinder or the system pressure. The parameter Relative velocity near to zero is used by the internal state machine of the cylinder model and determines the velocity below which the piston is considered stuck.

The pressure in both cylinder chambers can be initialized by assigning start values to Pressure in chamber A (bore side) and Pressure in chamber B (rod side). The parameter Dead volume determines the size of the parasitic volume which remains even if the piston has reached the mechanical stops at the cylinder ends.

The volumetric losses due to internal and external leakage are parameterized by providing the respective flow rates (Internal leakage: volume flow and External leakage: volume flow), associated pressure drops (Internal leakage: pressure difference and External leakage: pressure difference) and the fluid density Reference density for volume flow and pressure difference for which these values were obtained.

The fluid properties can be propagated between the two hydraulic ports by setting the parameter Forward fluid properties to "true".

Parameters

NameLabelDescriptionData TypeValid Values

mo_pistonDiameter

pistonDiameter

Piston diameter

Scalar

mo_rodDiameterA

rodDiameterA

Rod diameter @ port A

Scalar

mo_rodDiameterB

rodDiameterB

Rod diameter @ port B

Scalar

mo_cylinderLength

cylinderLength

Cylinder length

Scalar

mo_rodLengthA

rodLengthA

Rod length @ port A

Scalar

mo_rodLengthB

rodLengthB

Rod length @ port B

Scalar

mo_angle

angle

Inclination angle

Scalar

mo_deadVolume

deadVolume

Dead volume

Scalar

mo_massPiston

massPiston

Piston mass

Scalar

mo_massCylinder

massCylinder

Cylinder mass

Scalar

mo_stroke

stroke

stroke

Structure

mo_stroke/fixed

fixed

Cell of scalars

true
false

mo_stroke/start

start

Cell of scalars

mo_relVelocity

relVelocity

relVelocity

Structure

mo_relVelocity/fixed

fixed

Cell of scalars

true
false

mo_relVelocity/start

start

Cell of scalars

mo_pA

pA

pA

Structure

mo_pA/fixed

fixed

Cell of scalars

true
false

mo_pA/start

start

Cell of scalars

mo_pB

pB

pB

Structure

mo_pB/fixed

fixed

Cell of scalars

true
false

mo_pB/start

start

Cell of scalars

NameLabelDescriptionData TypeValid Values

mo_fProp

fProp

Velocity dependent friction

Scalar

mo_fCoulomb

fCoulomb

Constant friction/Coulomb force

Scalar

mo_fBreakaway

fBreakaway

Breakaway friction force

Scalar

mo_vM

vM

Velocity parameter for Stribeck friction

Scalar

mo_relFric

relFric

Use "relative friction factor" to calculate friction

Scalar

true
false

mo_relFricFactor

relFricFactor

Relative friction factor

Scalar

mo_vSmall

vSmall

Relative velocity near to zero

Scalar

mo_leakageFlowRateInternal

leakageFlowRateInternal

Internal leakage: volume flow

Scalar

mo_leakagePressureDiffInternal

leakagePressureDiffInternal

Internal leakage: pressure difference

Scalar

mo_leakageFlowRateExternal

leakageFlowRateExternal

External leakage: volume flow

Scalar

mo_leakagePressureDiffExternal

leakagePressureDiffExternal

External leakage: pressure difference

Scalar

mo_leakageReferenceDensity

leakageReferenceDensity

Reference density for volume flow and pressure difference

Scalar

NameLabelDescriptionData TypeValid Values

mo_forwardFluidProperties

forwardFluidProperties

Forward fluid properties between ports

Scalar

true
false

NameLabelDescriptionData TypeValid Values

mo__nmodifiers

Number of Modifiers

Specifies the number of modifiers

Number

mo__modifiers

Modifiers

Add new modifier

Structure

mo__modifiers/varname

Variable name

Cell of strings

mo__modifiers/attribute

Attribute

Cell of strings

'start'
'fixed'

mo__modifiers/value

Value

Ports

NameTypeDescriptionIO TypeNumber

flange_c

implicit

Cylinder flange

input

1

flange_pa

implicit

Piston flange @ port A

input

2

flange_pb

implicit

Piston flange @ port B

output

1

fluidPortA

implicit

Hydraulic port A

input

3

fluidPortB

implicit

Hydraulic port B

input

4

strokeOut

implicit

Relative position of piston

output

2