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Double-Acting Actuator (TL-G)

Linear actuator with opposing thermal liquid and gas chambers

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  • Double-Acting Actuator (TL-G) block

Libraries:
Simscape / Fluids / Thermal Liquid / Actuators

Description

The Double-Acting Actuator (TL-G) block models a linear actuator with opposing chambers of thermal liquid and gas. The chambers can be individually pressurized to power the actuator in both extension and retraction strokes. A piston between the chambers converts the pressure difference across them into actuation force.

The figure maps the conserving ports of the block to the actuator parts. Ports A and B are the inlets of the thermal liquid and gas chambers. Ports R and C are the translating piston and case. The chambers can exchange heat with the environment and are fitted for this purpose with ports HA and HB. The piston is perfectly insulating. The thermal liquid and gas chambers do not exchange heat with each other.

The sign of the piston displacement relative to the case depends on the mechanical orientation of the actuator. Use the Mechanical orientation parameter to specify this setting. If the mechanical orientation is positive, the piston displacement is positive when the pressure is highest in the thermal liquid chamber (port A). If the mechanical orientation is negative, the piston displacement (under the same pressure conditions) is negative.

Use port P to output the instantaneous piston position. The measurement is absolute (relative to zero). Hard stops limit the motion of the piston to the length of the case. The stops are modeled as spring-dampers, with spring and damping coefficients to capture material compliance. One is located at the bottom of the piston stroke and the other at the top:

  • If the Mechanical orientation setting is Positive, the bottom stop is at zero, and the top stop is at a distance equal to the piston stroke.

  • If the Mechanical orientation setting is Negative, the top stop is at zero, and the bottom stop is at a distance equal to the piston stroke.

The block is a composite component built from Simscape™ Foundation blocks. For more information on how the Double-Acting Actuator (TL-G) block works, see the reference pages of the constituent blocks:

Ports

Output

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Physical signal output port associated with the piston position. The measurement is absolute. The first reading is the value of the Piston initial displacement parameter.

Conserving

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Thermal liquid conserving port associated with the inlet to chamber A.

Gas conserving port representing the inlet to chamber B.

Mechanical translational conserving port representing the actuator piston.

Mechanical translational conserving port representing the actuator casing.

Thermal conserving port associated with the surface through which heat exchange can occur between the thermal liquid volume and the actuator surroundings. The thermal processes at this port influence the temperature in the thermal liquid chamber and therefore at port A.

Thermal conserving port associated with the surface through which heat exchange can occur between the gas volume and the actuator surroundings. The thermal processes at this port influence the temperature in the gas chamber and therefore at port A.

Parameters

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Thermal Liquid Side

Orientation of the actuator piston relative to the direction of fluid flow. A positive orientation causes the piston to move in the positive direction relative to the actuator casing in response to a positive flow rate through port A. The mechanical orientation affects the placement of the piston hard stops. See the block description for more information on the hard stop placement.

Area normal to the direction of flow in the body of the thermal liquid chamber. The block uses this area to calculate the hydraulic force due to the fluid pressure in the thermal liquid chamber. This parameter must be greater than zero.

Total distance of travel available to the piston, from one hard stop to the other. The hard stops limit the piston motion so that the piston is confined to stroke of the piston. See the block description for more information on the locations of the hard stops.

Absolute position of the piston at the start of simulation. The zero position coincides with the lower hard stop if the mechanical orientation is positive and with the upper hard stop if the mechanical orientation is negative.

Thermal liquid volume remaining in the thermal liquid chamber when the piston is pressed against the hard stop closest to the thermal liquid inlet. The dead volume enables the block to capture the internal states of the thermal liquid volume—its pressure and temperature—when this volume is at a minimum. This parameter must be greater than zero.

Option to model the effects of dynamic compressibility inside the thermal liquid chamber. The thermal liquid is treated as compressible if this parameter is set to On and as incompressible if it is set to Off. The block ignores the dependence of the thermal liquid density on pressure and temperature if Off is selected.

Pressure inside the thermal liquid chamber at simulation time zero relative to absolute zero. This parameter helps set the initial states of the thermal liquid volume.

Dependencies

This parameter is enabled when the Compressibility parameter is set to On.

Average temperature inside the thermal liquid chamber at the start of simulation. This parameter helps set the initial states of the thermal liquid volume.

Option to set the environment pressure of the thermal liquid chamber to the typical value of one earth atmosphere or to a custom value. Selecting Specified pressure exposes an additional parameter, Environment pressure, that you use to specify a custom pressure.

Pressure outside the thermal liquid chamber relative to absolute zero. This pressure acts against the pressure inside the thermal liquid chamber. A pressure of zero corresponds to a perfect vacuum.

Dependencies

This parameter is enabled when the Environment pressure specification is set to Specified pressure.

Gas Side

Area normal to the direction of flow in the body of the gas chamber. The block uses this area to calculate the pneumatic force due to the fluid pressure in the gas chamber. This parameter must be greater than zero.

Area normal to the direction of flow at the entrance to the gas chamber. The cross-sectional area at the entrance can differ from that in the body of the chamber. Set the two cross-sectional areas to different values to model the effects of a sudden area change at the inlet. This parameter must be greater than zero.

Gas volume remaining in the gas chamber when the piston is pressed against the hard stop closest to the gas inlet. The dead volume enables the block to capture the internal states of the gas volume—its pressure and temperature—when this volume is at a minimum. This parameter must be greater than zero.

Pressure inside the gas chamber at simulation time zero relative to absolute zero. This pressure helps set the initial state of the gas volume.

Option to set the environment pressure of the gas chamber to the typical value of one earth atmosphere or to a custom value. Selecting Specified pressure exposes an additional parameter, Environment pressure, that you use to specify a custom pressure.

Pressure outside the gas chamber relative to absolute zero. This pressure acts against the pressure inside the gas chamber. A pressure of zero corresponds to a perfect vacuum.

Dependencies

This parameter is enabled when the Environment pressure specification is set to Specified pressure.

Hard Stop

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

Piston stiffness coefficient.

Dependencies

To enable this parameter, set Hard stop model to

  • 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

Piston damping coefficient.

Dependencies

To enable this parameter, set Hard stop model to

  • 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

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.

Ratio of the final to the initial relative speed between the slider and the stop after the slider bounces.

Dependencies

To enable this parameter, set Hard stop model to Based on coefficient of restitution.

Threshold relative speed between slider and stop before collision. When the slider hits the case with speed less than the value of the Static contact speed threshold parameter, they stay in contact. Otherwise, the slider bounces. To avoid modeling static contact between the slider and the case, set this parameter to 0.

Dependencies

To enable this parameter, set Hard stop model to Based on coefficient of restitution.

Minimum force needed to release the slider from a static contact mode.

Dependencies

To enable this parameter, set Hard stop model to Based on coefficient of restitution.

Extended Capabilities

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

Version History

Introduced in R2016b

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See Also

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