Single-Acting Actuator (IL)

Single-acting linear actuator in an isothermal liquid network.

single acting actuator il

Description

The Single-Acting Actuator (IL) block models an actuator that converts the fluid pressure of port A into a mechanical force at port R by reciprocating movement of a piston. The motion of the piston is constrained by a rigid stop model. The position of the piston is calculated internally and transmitted to port p.

The parameters Initial piston displacement, Fluid dynamic compressibility and Environment pressure are user defined. Fluid inertia and mechanical inertia are not taken into account.

Displacement

Piston displacement is defined 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 is equal to Dead volume.

Rigid Restrictor Model

The limits of piston travel are proposed to be modelled in three ways. For this purpose, the block uses the same model as the block Translational Hard Stop, and takes into account the damping and stiffness coefficients at both ends of the piston stroke.

At the extreme positions of the piston, a rigid limiter force is generated, the region of effect of which is within the Transition region for Piston stroke or Piston initial displacement. Outside this region .

Damper

The block can model cushioning at the piston end positions. When Cylinder end cushioning is checked, the block takes into account the deceleration of the piston as it approaches the maximum piston stroke defined by Piston stroke. For more information on the hydraulic cylinder damper, see Cylinder Cushion (IL).

Friction

When Cylinder friction is checked, the block takes into account the friction of the piston as it moves, with the resultant friction being a combination of Stribeck, Coulomb and viscosity effects. The unit measures the pressure difference between the chamber pressure and the ambient pressure. For more information on the friction model and its limitations, see the block Cylinder Friction (IL).

Leakage

If Leakage is checked in the block, leakage through the gap between the chamber and the actuator piston is additionally taken into account. For more information on leakage modelling, see block Laminar Leakage (IL).

The flow rate is calculated as:

where

- kinematic viscosity of the fluid;
- piston length, p - ;
- port pressure A;
- ambient pressure, which is given by the parameter Environment pressure specification;
- 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 value of the Piston cross-sectional area parameter.

Numerical smoothing of area and pressure values

The computational robustness of the simulation is optionally adjusted by the Smoothing factor parameter. If Smoothing factor is not zero, the damper orifice area and check valve pressure values are smoothed. The orifice area changes smoothly between the parameters 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 sub-components

The Single-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.

single acting actuator il 1

Ports

Conserving

# A — inlet or outlet for fluid flow
isothermal liquid

Details

The port of an isothermal liquid corresponding to the inlet or outlet.

Program usage name

port

# 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

# 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

Determines the direction of piston displacement. Options for selection:

`Pressure at A causes positive displacement of R relative to C' - piston displacement 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 — cross-sectional area of the piston rod
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.

Values	`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`
Evaluatable	Yes

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

Details

Maximum possible piston travel.

Values	`m` \| `cm` \| `ft` \| `in` \| `km` \| `mi` \| `mm` \| `um` \| `yd`
Default value	`0.1 m`
Program usage name	`stroke`
Evaluatable	Yes

# Dead volume — volume of liquid 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

Liquid volume at piston movement value 0. This fluid volume corresponds to the position of the piston when it is up against the actuator end cap.

Values	`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`
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.

Values	`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

Model selection for the force acting on the piston when it is at the end positions. For more information, see the block 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.

Values	`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.

Values	`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'.

Values	`m` \| `cm` \| `ft` \| `in` \| `km` \| `mi` \| `mm` \| `um` \| `yd`
Default value	`0.1 mm`
Program usage name	`transition_region`
Evaluatable	Yes

Cushion

# Cylinder 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`
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