Double-Acting Actuator (IL)

Double-acting linear actuator in an isothermal liquid network.

double acting actuator il

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.

double acting actuator il 1

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

port_a

# 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

port_b

# R — actuator piston
translational mechanics

Details

A mechanical progressive port corresponding to the actuator piston.

Program usage name

rod_flange

# C — drive housing
translational mechanics

Details

Mechanical progressive port corresponding to the actuator housing.

Program usage name

case_flange

Output

# p — piston position
scalar

Details

Piston position in m.

Data types	`Float64`.
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	`true (switched on)`
Program usage name	`same_properties`
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	`Pressure at A causes positive displacement of R relative to C` \| `Pressure at A causes negative displacement of R relative to C`
Default value	`Pressure at A causes positive displacement of R relative to C`
Program usage name	`orientation`
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.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`0.01 m^2`
Program usage name	`piston_area_a`
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.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`0.01 m^2`
Program usage name	`piston_area_b`
Evaluatable	Yes

# Piston stroke — piston stroke
m | cm | ft | in | km | mi | mm | um | yd

Details

Maximum possible piston travel.

Units	`m` \| `cm` \| `ft` \| `in` \| `km` \| `mi` \| `mm` \| `um` \| `yd`
Default value	`0.1 m`
Program usage name	`stroke`
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.

Units	`l` \| `gal` \| `igal` \| `m^3` \| `cm^3` \| `ft^3` \| `in^3` \| `km^3` \| `mi^3` \| `mm^3` \| `um^3` \| `yd^3` \| `Nm/Pa` \| `Nm/bar` \| `lbfft/psi` \| `ftlbf/psi`
Default value	`1e-05 m^3`
Program usage name	`dead_volume_a`
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.

Units	`l` \| `gal` \| `igal` \| `m^3` \| `cm^3` \| `ft^3` \| `in^3` \| `km^3` \| `mi^3` \| `mm^3` \| `um^3` \| `yd^3` \| `Nm/Pa` \| `Nm/bar` \| `lbfft/psi` \| `ftlbf/psi`
Default value	`1e-05 m^3`
Program usage name	`dead_volume_b`
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	`Atmospheric pressure` \| `Specified pressure`
Default value	`Atmospheric pressure`
Program usage name	`pressure_type`
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.

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`0.101325 MPa`
Program usage name	`p_specified`
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	`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`
Default value	`Stiffness and damping applied smoothly through transition region, damped rebound`
Program usage name	`hardstop_model`
Evaluatable	No

# Hard stop stiffness coefficient — stiffness factor
N/m | lbf/ft | lbf/in

Details

Piston stiffness coefficient.

Units	`N/m` \| `lbf/ft` \| `lbf/in`
Default value	`1e10 N/m`
Program usage name	`k_hard_stop`
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.

Units	`kg/s` \| `N*s/m` \| `N/(m/s)` \| `lbf/(ft/s)` \| `lbf/(in/s)`
Default value	`150.0 N*s/m`
Program usage name	`C_hard_stop`
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'.

Units	`m` \| `cm` \| `ft` \| `in` \| `km` \| `mi` \| `mm` \| `um` \| `yd`
Default value	`0.1 mm`
Program usage name	`transition_region`
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	`false (switched off)`
Program usage name	`enable_cylinder_cushion_a`
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