Rotating Single-Acting Actuator (IL)

R2026b

Actuator on a rotating shaft in an isothermal liquid network

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  • Rotating Single-Acting Actuator (IL) block

Libraries:
Simscape / Fluids / Isothermal Liquid / Actuators

Description

The Rotating Single-Acting Actuator (IL) block models an actuator that rotates around its central axis in an isothermal liquid network. Rotating shaft control components such as friction clutches or brakes may use rotating actuators. The fluid enters the actuator at port A. The angular velocity is set at port W. Port C is associated with the actuator casing and the piston velocity and force are set at port R.

When the block internally calculates the piston position, port p outputs the piston position. When a connection to a Simscape™ Multibody™ joint sets the position, the block receives the position as a physical signal at port p. One of four hard stop models limits the motion of the piston when it is near full extension or full retraction.

Geometry

The cylinder chamber of the actuator is an annulus with an inner radius equal to the value of the Piston inner radius parameter and an outer radius equal to the value of the Piston outer radius parameter. The fluid enters the cylinder chamber at the radius specified by the Fluid channel length parameter. The fluid enters the entire component along the axis of rotation. The value of the Fluid channel length parameter must be between the value of the Piston inner radius and Piston outer radius parameters.

Displacement

The piston displacement is measured 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. If you specify the displacement with an input, ensure that the derivative of the position is equal to the piston velocity. If you specify the input with a Translational Multibody Interface block connection to a Simscape Multibody joint, this requirement is met.

Hard Stop Model

To avoid mechanical damage to an actuator when it is fully extended or fully retracted, an actuator typically has nonlinear behavior when the piston approaches these limits. The Rotating Single-Acting Actuator (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 block models the hard stop force when the piston is at its upper or lower bound. The boundary region is within the value of the Transition region parameter relative to the value of the Piston stroke parameter or the piston initial displacement. Outside of this region, FHardStop=0.

For more information about these settings, see the Translational Hard Stop block page.

Block Subcomponents

The Rotating Single-Acting Actuator (IL) block is a composite component that comprises three blocks:

  • Rotating Channel (IL) — This subcomponent moves the fluid from a radius of 0 to a radius equal to the value of the Fluid channel length parameter and accounts for the pressure change due to the centrifugal effect of the change in radius.

  • Single-Acting Actuator (IL) — This subcomponent calculates the actuator force from the pressure of the fluid that enters the cylinder chamber, which includes the centrifugal effect of moving the fluid to the fluid channel length.

  • Rotating Cylinder Force (IL) — The fluid inside the chamber has a pressure gradient due to the centrifugal effect. This subcomponent accounts for the change in the actuator force due to the pressure gradient relative to the pressure at the radius equal to the value of the Fluid channel length parameter.

This figure shows the functional block diagram for the Rotating Single-Acting Actuator (IL) block.

Block composite component diagram

Examples

Rotating Hydraulic Actuator

Rotating Hydraulic Actuator

Uses a Rotating Single-Acting Actuator (IL) block to model a hydraulic cylinder actuator for operating friction clutches, brakes, and other devices installed on rotating shafts. A key element of the actuator is a piston that moves back and forth under an axial force that consists of the static pressure force and a rotating cylinder force developed by centrifugal force on the rotating fluid.

Ports

Conserving

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Inlet port to the liquid chamber. The block assumes that port A is located along the axis of rotation where the radius is zero.

Programmatic Use

Port: A

Reference port for actuator velocity and force.

Programmatic Use

Port: C

Port associated with the piston velocity and force.

Programmatic Use

Port: R

Input

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Actuator rotational velocity, specified as a physical signal in rad/s.

Programmatic Use

Port: W

Piston position in m, specified as a physical signal from a Simscape Multibody block.

Dependencies

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

Programmatic Use

Port: p_in

Output

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Piston position in m, returned as a physical signal.

Dependencies

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

Programmatic Use

Port: p_out

Parameters

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Actuator

Piston outer radius.

Programmatic Use

Parameter: r_outer

Piston inner radius.

Programmatic Use

Parameter: r_inner

Option for 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.

Programmatic Use

Parameter: mech_orientation
Values: "foundation.enum.MechOrientationTranslational.Positive" | "foundation.enum.MechOrientationTranslational.Negative"

Maximum piston travel distance.

Programmatic Use

Parameter: stroke

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

Programmatic Use

Parameter: dead_volume

Environment reference pressure. The Atmospheric pressure option sets the environmental pressure to 0.101325 MPa.

Programmatic Use

Parameter: pressure_spec
Values: "foundation.enum.pressure_spec.atmospheric" | "foundation.enum.pressure_spec.specified"

User-defined environmental pressure.

Dependencies

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

Programmatic Use

Parameter: environment_pressure

Fluid Channel

Radius where fluid enters the cylinder chamber. This value must be greater than or equal to the Piston inner radius and less than or equal to the Piston outer radius.

Programmatic Use

Parameter: r_fluid

Cross-sectional area of the fluid channel.

Programmatic Use

Parameter: area_fluid

Flow discharge loss coefficient.

Programmatic Use

Parameter: Cd

Upper Reynolds number limit for laminar flow through the orifice.

Programmatic Use

Parameter: Re_c

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.

Programmatic Use

Parameter: hardstop_model
Values: "simscape.enum.hardstop.smooth" | "simscape.enum.hardstop.fullundamped" | "simscape.enum.hardstop.fulldamped" | "simscape.enum.hardstop.modechart"

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

Programmatic Use

Parameter: stiff_coeff

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

Programmatic Use

Parameter: damping_coeff

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.

Programmatic Use

Parameter: transition

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.

Programmatic Use

Parameter: coeff_rest

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.

Programmatic Use

Parameter: v_tol

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.

Programmatic Use

Parameter: f_tol

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.

Programmatic Use

Parameter: displacement_spec
Values: "foundation.enum.DisplacementSpec.Calculate" | "foundation.enum.DisplacementSpec.InputSignal"

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.

Programmatic Use

Parameter: x0

Whether to model the dynamic compressibility of the liquid. Dynamic compressibility affects the transient response of the system at small timescales. If you select this parameter, the pressure responds dynamically based on the accumulation of fluid mass in the volume. If you clear this 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.

Programmatic Use

Parameter: dynamic_compressibility
Values: "true" | "false"

Starting liquid pressure for compressible fluids.

Dependencies

To enable this parameter, select Enable dynamic compressibility.

Programmatic Use

Parameter: p0

Liquid pressure at nominal operating conditions. The block uses this value to calculate the nominal density to use in the mass conservation equation when dynamic compressibility is disabled.

Dependencies

To enable this parameter, clear the Enable dynamic compressibility checkbox.

Programmatic Use

Parameter: p_nominal

Extended Capabilities

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

Version History

Introduced in R2020a

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See Also

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