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Single-Acting Actuator (TL)

Single-acting linear actuator in a thermal liquid system

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  • Simscape / Fluids / Thermal Liquid / Actuators

  • Single-Acting Actuator (TL) block

Description

The Single-Acting Actuator (TL) block represents a linear actuator with piston motion controlled by a single thermal liquid chamber. The actuator generates force in the extension and retraction strokes, but the actuation force depends on the gauge pressure at a single chamber.

The figure shows the key components of an actuator. Port A represents the thermal liquid chamber inlet. Port R represents the translating actuator piston, and port C represents the actuator case. Port H represents the thermal interface between the thermal liquid chamber and the environment.

Single-Acting Actuator Schematic

Displacement

The block measures the piston displacement as the position at port R relative to port C. The Mechanical orientation parameter identifies the direction of piston displacement. The piston displacement is neutral, or 0, when the chamber volume is equal to the value of the Dead volume parameter. When you input the piston displacement using port p, ensure that the derivative of the position is equal to the piston velocity. This is automatically the case when you use a Translational Multibody Interface block connection to a Simscape Multibody joint.

The direction of the piston motion depends on the Mechanical orientation parameter. If the mechanical orientation is positive, then a positive gauge pressure at port A yields a positive piston translation relative to the actuator case. The direction of motion reverses for a negative mechanical orientation.

Hard Stop

A set of hard stops limit the piston range of motion. The block uses an implementation of the Translational Hard Stop block, which treats hard stops like spring-damper systems. The spring stiffness coefficient controls the restorative component of the hard-stop contact force and the damping coefficient the dissipative component.

The hard stops are located at the distal ends of the piston stroke. If the mechanical orientation is positive, then the lower hard stop is at x = 0, and the upper hard stop is at x = +stroke. If the mechanical orientation is negative, then the lower hard stop is at x = -stroke, and the upper hard stop is at x = 0.

Block Composite

This block is a composite component based on the Simscape™ Foundation blocks:

Composite Component Diagram

Ports

Input

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Physical signal input associated with the piston position, in m. Connect this port to a Simscape Multibody™ network using a Translational Multibody Interface block.

Dependencies

To enable this port, set Piston displacement to Provide input signal from Multibody joint.

Output

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Physical signal output associated with the piston position, in m.

Dependencies

To enable this port, set Piston displacement to Calculate from velocity of port R relative to port C.

Conserving

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Thermal liquid conserving port associated with chamber A.

Translational mechanical conserving port associated with the actuator casing.

Translational mechanical conserving port associated with the actuator piston.

Thermal liquid conserving port associated with the thermal mass of the liquid volume.

Parameters

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Actuator

Sets the piston displacement direction. When you set this parameter to:

  • Pressure at A causes positive displacement of R relative to C, the piston displacement is positive when the volume of liquid at port A is expanding. This corresponds to rod extension.

  • Pressure at A causes negative displacement of R relative to C, the piston displacement is negative when the volume of liquid at port A is expanding. This corresponds to rod contraction.

Cross-sectional area of the piston rod.

Maximum piston travel distance.

Volume of liquid when the piston displacement is 0. This is the liquid volume when the piston is up against the actuator end cap.

Environment reference pressure. When you select Atmospheric pressure, the block assumes a pressure of 0.101325 MPa.

User-defined environmental pressure.

Dependencies

To enable this parameter, set Environment pressure specification to Specified pressure.

Hard Stop

Piston stiffness coefficient.

Piston damping coefficient.

Model choice for the force on the piston at full extension or full retraction. See the Translational Hard Stop block for more information.

Application range of the hard stop force model. Outside of this range of the piston maximum extension and piston maximum retraction, the Hard stop model is not applied and there is no additional force on the piston.

Dependencies

To enable this parameter, set Hard stop model to Stiffness and damping applied smoothly through transition region, damped rebound.

Initial Conditions

Method for determining the piston position. The block can receive the position from a Multibody block when set to Provide input signal from Multibody joint, or calculates the position internally and reports the position at port p. The position is between 0 and the Piston stroke when the mechanical orientation is positive and 0 and –Piston stroke when the mechanical orientation is negative.

Piston position at the start of the simulation.

Dependencies

To enable this parameter, set Piston displacement to Calculate from velocity of port R relative to port C.

Whether to model any change in fluid density due to fluid compressibility. When Fluid compressibility is set to On, changes due to the mass flow rate into the block are calculated in addition to density changes due to changes in pressure. In the Isothermal Liquid Library, all blocks calculate density as a function of pressure.

Initial temperature of the liquid volume in the actuator.

Starting liquid pressure for compressible fluids.

Dependencies

To enable this parameter, set Fluid dynamic compressibility to On.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2016a