Translational Mechanical Converter (IL-PB)

Interface between isothermal liquid and position-based mechanical translational networks

Since R2026a

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Libraries:
Simscape / Foundation Library / Isothermal Liquid / Elements

Description

The Translational Mechanical Converter (IL-PB) block models an interface between an isothermal liquid network and a position-based mechanical translational network. The block converts isothermal liquid pressure into mechanical force. Use this block to build position-based linear actuators.

The converter contains a variable volume of liquid. If you select the Enable dynamic compressibility check box, then the pressure evolves based on the dynamic compressibility of the liquid volume.

Port A is the isothermal liquid conserving port associated with the converter inlet. Ports B and F are the position-based translational ports associated with the base and follower, respectively.

Mass Balance

The mass conservation equations in the mechanical converter volume are

$$\begin{array}{l}{\dot{m}}_{\text{A}}=\{\begin{array}{cc}{\rho }_{I}Sv,& \text{if}\text{fluid}\text{dynamic}\text{compressibility}\text{is}\text{off}\\ {\rho }_{I}Sv+\frac{1}{{\beta }_I}\frac{d{p}_I}{dt}{\rho }_{I}V,& \text{if}\text{fluid}\text{dynamic}\text{compressibility}\text{is}\text{on}\end{array}\\ v=\frac{dx}{dt}\\ v=v_F-v_B\\ V=V_{dead}+Sx\end{array}$$

where:

• $${\dot{m}}_{\text{A}}$$ is the mass flow rate into the converter through port Af.

• ρ_I is the fluid density inside the converter.

• β_I is the fluid bulk modulus inside the converter.

• S is the cross-sectional area of the converter interface.

• v is the translational velocity of the converter interface.

• v_F and v_B are the translational velocities of ports F and B, respectively.

• x is the displacement of the converter interface.

• V is the liquid volume inside the converter.

• V_dead is the dead volume, that is, volume of liquid when the interface displacement is 0.

• p_I is the pressure inside the converter.

Equations used to compute the fluid mixture density and bulk modulus depend on the selected isothermal liquid model. For detailed information, see Isothermal Liquid Modeling Options.

Momentum Balance

The momentum conservation equation in the mechanical converter volume is

$$F=(p-p_{\text{env}})S,$$

where:

• F is the force the liquid exerts on the converter interface.

• p_env is the environment pressure outside the converter.

Variables

To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see Modify Nominal Values for a Block Variable.

Ports

Conserving

Af — Converter inlet

isothermal liquid

Isothermal liquid conserving port associated with the converter inlet.

B — Base port

position-based mechanical translational

Position-based mechanical translational conserving port that represents the base connection.

F — Follower port

position-based mechanical translational

Position-based mechanical translational conserving port that represents the follower connection. For positive length, port F has a more positive position than port B.

Parameters

Interface cross-sectional area — The area on which the liquid exerts pressure to generate the translational force

0.01 m^2 (default) | positive scalar

The area on which the liquid exerts pressure to generate the translational force.

Dead volume — Volume of liquid when the interface displacement is 0

1e-5 m^3 (default) | positive scalar

Volume of liquid when the interface displacement is 0.

Environment pressure specification — Select a specification method for the environment pressure

Atmospheric pressure (default) | Specified pressure

Select a specification method for the pressure outside the converter:

• Atmospheric pressure — Use the atmospheric pressure, specified by the Isothermal Liquid Properties (IL) block connected to the circuit.

• Specified pressure — Specify a value by using the Environment pressure parameter.

Environment pressure — Pressure outside the converter

0.101325 MPa (default) | positive scalar

Pressure outside the converter acting against the pressure of the converter liquid volume. A value of 0 indicates that the converter expands into vacuum.

Dependencies

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

Enable dynamic compressibility — Select whether to model fluid dynamic compressibility

On (default) | Off

Whether to model the dynamic compressibility of the liquid. Dynamic compressibility impacts the transient response of the system at small time scales. If you select this parameter, the pressure responds dynamically based on the accumulation of fluid mass in the volume. If you clear the parameter, the volume does not accumulate mass and the pressure response is instantaneous. Clearing this setting can improve simulation performance, but may have a negative effect on the simulation robustness. Only clear this setting for small fluid volumes or models with long simulation times.

Initial liquid pressure — Liquid pressure at time zero

0.101325 MPa (default) | positive scalar

Liquid pressure in the converter at the start of simulation.

Dependencies

To enable this parameter, select the Enable dynamic compressibility check box.

Extended Capabilities

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

Version History

Introduced in R2026a