Double-Acting Actuator (IL)
Double-acting linear actuator in an isothermal liquid network.
Description
The Double-Acting Actuator (IL) block models an actuator that converts the pressure drop between two chambers into piston movement. The piston movement is controlled by the differential pressure on both sides of the plate separating the chambers of the block. The limits of piston travel are modelled by one of the rigid stop models. Fluid compressibility is additionally modelled in both piston chambers.
Ports A and B represent inlets for isothermal liquid. Port C is associated with the actuator body and port R is associated with the piston, while it returns the piston velocity. The piston position is calculated internally and transferred to port p.
The direction of piston movement is set by the Mechanical orientation parameter. If the Mechanical orientation parameter is set to Pressure at A causes positive displacement of R relative to C
, the piston extends at a positive differential pressure - . If the Mechanical orientation is set to Pressure at A causes negative displacement of R relative to C
, the piston retracts at positive differential pressure between the chambers.
Displacement
The displacement of the piston is determined by the displacement of port R relative to port C. The value of the Mechanical orientation parameter determines the direction of piston displacement. Piston displacement is neutral (equal to 0
) when the chamber volume A is equal to Dead volume.
Rigid Restrictor Model
At the extreme positions of the piston, the block models the non-linear position of the actuator. For this purpose, the block uses the same models as the block Translational Hard Stop.
At the extreme positions of the piston, a rigid limiter force is generated, whose area of effect is within the Transition region for Piston stroke or Piston initial displacement. Outside this region .
Damper
The block can simulate damping at the extreme positions of the piston. If Cylinder A end cushioning and/or Cylinder B end cushioning is checked, the block takes into account the deceleration of the piston as it approaches the maximum value of the piston stroke length defined by the Piston stroke parameter. For more information on the hydraulic cylinder damper, see the block Cylinder Cushion (IL).
Friction
When Cylinder friction effect is checked, the block accounts for the friction of the piston as it moves, with the resulting friction being a combination of Stribeck, Coulomb and viscosity effects. The block measures the pressure difference between the pressure in the chamber and the ambient pressure. For more information on the friction model and its limitations, see the block Cylinder Friction (IL).
Leakage
The block allows you to account for possible leaks between chambers A and B. If the fluid in both chambers is the same (the Same fluid on both sides and Internal leakage checkboxes are selected), Poiseuille flow is modelled between the piston and cylinder. For more information on leakage modelling, see Laminar Leakage (IL).
Where.
-
- kinematic viscosity of the fluid;
-
- piston length, p - ;
-
- pressure in port A;
-
- port pressure B;
-
- cylinder diameter, which can be written as , where is the value of the Piston-cylinder clearance parameter;
-
- piston diameter, which can be calculated as , where is the average value of the parameters Piston cross-sectional area in chamber A and Piston cross-sectional area in chamber B.
Numerical smoothing of area and pressure values
The computational robustness of the simulation is optionally controlled by the Smoothing factor parameter. If the Smoothing factor is not zero, the orifice area of dampers A and B and the pressure range of the check valve are smoothed. The orifice area changes smoothly between Leakage area between plunger and cushion sleeve and Cushion plunger cross-sectional area. The valve pressure varies smoothly between Check valve cracking pressure differential and Check valve maximum pressure differential.
Block diagram
The Double-Acting Actuator (IL) block consists of four isothermal liquid library blocks and two Mechanics library blocks:
The structure diagram of the actuator is shown in the schematic diagram.
Saving the pulse
The conservation of momentum equation for the actuator is as follows:
where
-
- is the force exerted by the fluid on the transducer surface. This value does not take into account the forces from the subcomponents of the unit: rigid restrictor (Translational Hard Stop), cylinder damper Cylinder Cushion (IL), cylinder friction Cylinder Friction (IL). For the contribution of these forces to the converter surface, refer to the documentation pages for these subcomponents;
-
depends on the value of the Mechanical orientation parameter:
-
If the Mechanical orientation parameter is set to
Pressure at A causes positive displacement of R relative to C
, then ; -
If the Mechanical orientation parameter is set to
Pressure at A causes negative displacement of R relative to C
, then ;
-
-
- the cross-sectional area of the stem bore, which can be calculated as ;
-
- value of the parameter Piston cross-sectional area in chamber A;
-
- the value of Piston cross-sectional area in chamber B;
-
- pressure inside chamber A;
-
- pressure inside chamber B;
-
- ambient pressure.
Ports
Conserving
#
A
—
inlet for fluid flow into the chamber A
isothermal liquid
Details
isothermal liquid port corresponding to the inlet to chamber A.
Program usage name |
|
#
B
—
inlet for fluid flow into the chamber B
isothermal liquid
Details
isothermal liquid port corresponding to the inlet to chamber B.
Program usage name |
|
#
R
—
actuator piston
translational mechanics
Details
A mechanical progressive port corresponding to the actuator piston.
Program usage name |
|
#
C
—
drive housing
translational mechanics
Details
Mechanical progressive port corresponding to the actuator housing.
Program usage name |
|
Output
#
p
—
piston position
scalar
Details
Piston position in m.
Data types |
|
Complex numbers support |
No |
Parameters
Actuator
# Same fluid on both sides — whether the same fluid is modelled in both chambers of the unit
Details
Whether the same fluid is modelled on both sides of the block. If the checkbox is selected, the fluid properties are propagated through the block. If unchecked, the chambers in the block are connected to isolated networks of fluids with different properties.
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Mechanical orientation —
piston travel direction
Pressure at A causes positive displacement of R relative to C
| Pressure at A causes negative displacement of R relative to C
Details
Defines the direction of piston movement. Options for selection:
-
`Pressure at A causes positive displacement of R relative to C' - piston movement is positive if the fluid volume in port A increases. This corresponds to the movement of the rod out of the cylinder.
-
Pressure at A causes negative displacement of R relative to C
- piston movement is negative if the volume of fluid in port A increases. This corresponds to movement of the rod inside the cylinder.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Piston cross-sectional area in chamber A —
cross-sectional area of the chamber piston rod A
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
Cross-sectional area of the piston rod on the chamber side A.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Piston cross-sectional area in chamber B —
cross-sectional area of the chamber piston rod B
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
Cross-sectional area of the piston rod on the chamber side B.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Piston stroke —
piston stroke
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
Maximum possible piston travel.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Dead volume in chamber A —
volume of liquid in chamber A, at which piston movement is equal to 0
l
| gal
| igal
| m^3
| cm^3
| ft^3
| in^3
| km^3
| mi^3
| mm^3
| um^3
| yd^3
| N*m/Pa
| N*m/bar
| lbf*ft/psi
| ft*lbf/psi
Details
Volume of liquid in chamber A at piston movement value 0
. This fluid volume corresponds to the position of the piston at which it is up against the actuator end cap.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Dead volume in chamber B —
volume of liquid in the chamber B, at which the piston movement is equal to 0
l
| gal
| igal
| m^3
| cm^3
| ft^3
| in^3
| km^3
| mi^3
| mm^3
| um^3
| yd^3
| N*m/Pa
| N*m/bar
| lbf*ft/psi
| ft*lbf/psi
Details
Volume of liquid in chamber B at piston movement value `0'. This fluid volume corresponds to the position of the piston at which it is up against the actuator end cap.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Environment pressure specification —
method of setting the ambient pressure
Atmospheric pressure
| Specified pressure
Details
Method of setting the ambient pressure. The Atmospheric pressure
option sets the ambient pressure to 0.101325 MPa
.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Environment pressure —
ambient pressure
Pa
| GPa
| MPa
| atm
| bar
| kPa
| ksi
| psi
| uPa
| kbar
Details
User-defined ambient pressure.
Dependencies
To use this parameter, set Environment pressure specification to Specified pressure
.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Hard Stop
#
Hard stop model —
selecting the model of the hard stop
Stiffness and damping applied smoothly through transition region, damped rebound
| Full stiffness and damping applied at bounds, undamped rebound
| Full stiffness and damping applied at bounds, damped rebound
Details
Selects the model for the force acting on the piston when it is at the end positions. See block for more information Translational Hard Stop
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Hard stop stiffness coefficient —
stiffness factor
N/m
| lbf/ft
| lbf/in
Details
Piston stiffness coefficient.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Hard stop damping coefficient —
damping factor
kg/s
| N*s/m
| N/(m/s)
| lbf/(ft/s)
| lbf/(in/s)
Details
Piston damping factor.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Transition region —
range of action of the rigid stop model
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
The operating range of the hard stop model. Outside this range, the Hard stop model does not apply to the extreme piston positions and no additional force is applied to the piston from the stop.
Dependencies
To use this parameter, set the Hard stop model to `Stiffness and damping applied smoothly through transition region, damped rebound'.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Cushion A
# Cylinder A end cushioning — option to simulate piston braking due to damper action
Details
Whether the deceleration of the piston at its extreme positions is taken into account. For more information, see the block see the block Cylinder Cushion (IL).
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Cushion plunger cross-sectional area —
cross-sectional area of the damping plug
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
Cross-sectional area of the damping plug.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Cushion plunger length —
damping plug length
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
Length of the damping plug.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Cushion orifice area —
area of the opening between the damper chambers
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
The area of the opening between the damper chambers.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Leakage area between plunger and cushion sleeve —
clearance area between damper plug and bushing
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
The clearance area between the damper plunger and the sleeve. The parameter maintains the computational stability of the simulation by ensuring flow continuity.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve cracking pressure differential —
differential pressure at which the check valve starts to open
Pa
| GPa
| MPa
| atm
| bar
| kPa
| ksi
| psi
| uPa
| kbar
Details
The pressure above which the damper actuates. When the pressure difference between port A and meets or exceeds this parameter, the damper check valve starts to open.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve maximum pressure differential —
pressure drop required to fully open the check valve
Pa
| GPa
| MPa
| atm
| bar
| kPa
| ksi
| psi
| uPa
| kbar
Details
Maximum differential pressure of the damper check valve. This parameter sets the upper pressure limit so that the system pressure remains realistic.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve maximum area —
area of fully open check valve
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
The cross-sectional area of the check valve orifice in the fully open position.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve leakage area —
leakage area with fully closed check valve
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
Total possible leakage area with the check valve fully closed. Any area smaller than this value increases smoothly to the specified leakage area. This value contributes to computational stability by maintaining flow continuity.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
# Smoothing factor — numerical smoothing factor
Details
Continuous smoothing factor that provides a smooth opening by correcting the valve characteristic in the nearly open and nearly closed positions. Set a non-zero value less than one to increase the stability of the simulation.
Dependencies
To use this parameter, select the Cylinder A end cushioning checkbox.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Cushion B
# Cylinder B end cushioning — option to simulate piston braking due to damper action
Details
Whether the deceleration of the piston at its extreme positions is taken into account. For more information, see the block see the block Cylinder Cushion (IL).
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Cushion plunger cross-sectional area —
cross-sectional area of the damping plug
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
Cross-sectional area of the damping plug.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Cushion plunger length —
damping plug length
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
Length of the damping plug.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Cushion orifice area —
area of the opening between the damper chambers
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
The area of the opening between the damper chambers.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Leakage area between plunger and cushion sleeve —
clearance area between damper plug and bushing
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
The clearance area between the damper plunger and the sleeve. The parameter maintains the computational stability of the simulation by ensuring flow continuity.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve cracking pressure differential —
differential pressure at which the check valve starts to open
Pa
| GPa
| MPa
| atm
| bar
| kPa
| ksi
| psi
| uPa
| kbar
Details
The pressure above which the damper actuates. When the pressure difference between port B and meets or exceeds the value of this parameter, the damper check valve starts to open.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve maximum pressure differential —
pressure drop required to fully open the check valve
Pa
| GPa
| MPa
| atm
| bar
| kPa
| ksi
| psi
| uPa
| kbar
Details
Maximum differential pressure of the damper check valve. This parameter sets the upper pressure limit so that the system pressure remains realistic.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve maximum area —
area of fully open check valve
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
The cross-sectional area of the check valve orifice in the fully open position.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Check valve leakage area —
leakage area with fully closed check valve
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
Details
Total possible leakage area with the check valve fully closed. Any area smaller than this value increases smoothly to the specified leakage area. This value contributes to computational stability by maintaining flow continuity.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
# Smoothing factor — numerical smoothing factor
Details
Continuous smoothing factor that provides a smooth opening by correcting the valve characteristic in the nearly open and nearly closed positions. Set a non-zero value less than one to increase the stability of the simulation.
Dependencies
To use this parameter, select the Cylinder B end cushioning checkbox.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Friction
# Cylinder friction effect — option for modelling friction during piston movement
Details
Whether the friction of the piston during movement is taken into account. The block friction force is made up of the Stribeck force, Coulomb force and viscosity. For more information, see block Cylinder Friction (IL).
Default value |
|
Program usage name |
|
Evaluatable |
No |
# Breakaway to Coulomb friction force ratio — the ratio of the detachment force to the Coulomb friction force
Details
The ratio of the detachment force to the Coulomb friction force.
Dependencies
To use this parameter, select the Cylinder friction effect checkbox.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Breakaway friction velocity —
friction threshold
fpm
| fps
| kph
| mph
| m/s
| cm/s
| ft/s
| in/s
| km/s
| mi/s
| mm/s
Details
The threshold value of velocity at which anti-friction motion begins.
Dependencies
To use this parameter, select the Cylinder friction effect checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Preload force —
initial force in the cylinder during seal assembly, N
N
| kN
| lb
| mN
| dyn
| lbf
Details
Initial force in the cylinder due to the seal assembly. The unit uses this parameter to calculate the Coulomb friction force.
Dependencies
To use this parameter, select the Cylinder friction effect checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Coulomb friction force coefficient —
Coulomb friction force coefficient
m^2
| cm^2
| ft^2
| in^2
| km^2
| mi^2
| mm^2
| um^2
| yd^2
| N/Pa
Details
Coulomb friction force coefficient.
Dependencies
To use this parameter, select the Cylinder friction effect checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Viscous friction coefficient —
viscous friction coefficient
kg/s
| N*s/m
| N/(m/s)
| lbf/(ft/s)
| lbf/(in/s)
Details
Coefficient of viscous friction.
Dependencies
To use this parameter, select the Cylinder friction effect checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Leakage
# Internal leakage — annular leakage modelling option
Details
Whether leakage through the annular gap between actuator chamber and piston is taken into account under reference ambient conditions. The flow through the gap is laminar. For more information, see block Laminar Leakage (IL).
Dependencies
To use this parameter, select the Same fluid on both sides checkbox.
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Piston-cylinder clearance —
radial clearance
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
The radial distance between the piston rod and the cylinder body.
Dependencies
To use this parameter, select the Same fluid on both sides and Internal leakage checkboxes.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Piston head length —
piston head length
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
Length of the piston head.
Dependencies
To use this parameter, select the Same fluid on both sides and Internal leakage checkboxes.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Initial Conditions
#
Initial piston displacement from chamber A cap —
initial position of the piston relative to the chamber cover A
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
Piston position relative to the chamber lid A at the beginning of the simulation.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
# Fluid dynamic compressibility — fluid compressibility modelling option
Details
Account for changes in fluid density due to fluid compressibility. When Fluid dynamic compressibility is checked, changes due to the mass flow rate of the fluid in the block are calculated in addition to density changes due to pressure changes. In the isothermal liquid library, all blocks calculate density as a function of pressure.
Default value |
|
Program usage name |
|
Evaluatable |
No |
#
Initial liquid pressure in chamber A —
initial fluid pressure for compressible liquids in the chamber A
Pa
| GPa
| MPa
| atm
| bar
| kPa
| ksi
| psi
| uPa
| kbar
Details
Initial fluid pressure for compressible liquids in chamber A.
Dependencies
To use this parameter, select the Fluid dynamic compressibility checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Initial liquid pressure in chamber B —
initial fluid pressure for compressible liquids in the chamber B
Pa
| GPa
| MPa
| atm
| bar
| kPa
| ksi
| psi
| uPa
| kbar
Details
Initial fluid pressure for compressible liquids in chamber B.
Dependencies
To use this parameter, select the Fluid dynamic compressibility checkbox.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |