Double-Acting Actuator (G-IL)
R2026bLinear actuator with isothermal liquid and gas chambers
Double-Acting Actuator (G-IL) block
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Libraries:
Simscape /
Fluids /
Isothermal Liquid /
Actuators
Description
The Double-Acting Actuator (G-IL) block represents an isothermal liquid chamber and a gas chamber separated by a piston plate. The piston actuation is controlled by the pressure differential between the chambers. The motion of the piston when it is near full extension or full retraction is limited by one of four hard stop models.
Port A is the isothermal liquid inlet and port B is the gas inlet. Connect elements for heat transfer between the gas chamber and the environment to port H. Port C acts as a mechanical translational reference for the actuator casing. Port R is associated with the actuator piston. The piston position is reported at port P.
This diagram shows the block behavior when Mechanical Orientation
is Pressure at A causes positive displacement of R relative to
C.
Displacement
The piston displacement is measured as the position at port R relative
to port C. The Mechanical orientation
identifies the direction of piston displacement. The piston displacement is neutral,
or 0, when the chamber volume is equal to the chamber dead
volume. When displacement is received as an input, ensure that the derivative of the
position is equal to the piston velocity. This is automatically the case when the
input is received from a Translational Multibody Interface block
connection to a Simscape™
Multibody™ joint.
Hard Stop Model
To avoid mechanical damage to the piston when it is fully extended or fully retracted, an actuator typically displays nonlinear behavior when the piston approaches these limits. The Double-Acting Actuator (G-IL) block models this behavior with a choice of four hard stop models, which model the material compliance through a spring-damper system. The hard stop models are:
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.Based on coefficient of restitution
The hard stop force is modeled when the piston is at its upper or lower bound. The boundary region is within the Transition region of the Piston stroke or piston initial displacement. Outside of this region,
For more information about these settings, see the Translational Hard Stop block page.
Block Schematic
The Double-Acting Actuator (G-IL) block is a composite of four Simscape Foundation blocks:
Examples
This example shows how to use a Double-Acting Actuator (G-IL) block to represent a double-acting actuator that implements an isothermal liquid port and gas port to control piston movement.
Examine the Model
Open the model.
In the model, the Pressure Source (IL) block represents the pressure applied to the isothermal liquid side of the piston within the actuator cylinder. The Pressure Source (G) block represents the pressure applied to the gas side of the piston within the actuator cylinder. The Mass block represents a 1kg mass moved by the piston.
The Double-Acting Actuator (G-IL) block receives input from the Pressure Source (IL) block from time T = 0 to T = 30 seconds, which causes a positive displacement of the piston. The Double-Acting Actuator (G-IL) block then receives input from the Pressure Source (G) block from time T = 30 to T = 60 seconds, which causes a negative displacement of the piston.
You can adjust the pressure input values by modifying the parameters in the Pressure Input (IL) and Pressure Input (G) blocks.
Simulate the Model
The Piston Position [m] block plots the measured piston position over time.
Observe that positive and negative piston displacements are limited by hardstops at 0.5 m and 0 m, respectively.
