Double-Acting Rotary Actuator (IL)

Double-acting rotary actuator in an isothermal liquid system

Since R2020a

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Libraries:
Simscape / Fluids / Isothermal Liquid / Actuators

Description

The Double-Acting Rotary Actuator (IL) block models a rotary actuator in an isothermal liquid network. The actuator converts the pressure differential between two chambers into mechanical torque. The motion of the piston when it is near full extension or full retraction is limited by one of four hard stop models.

Ports A and B are the isothermal liquid conserving ports associated with inlets of chamber A and chamber B, respectively. Port R is associated with the actuator shaft and port C is associated with the reference actuator casing. If Mechanical orientation is set to Pressure at A causes positive rotation of R relative to C, the pressure in chamber A causes a positive rotation of the shaft at port R relative to port C. When the shaft angle is calculated internally, the physical signal port q reports the shaft angle. When the angle is set by a connection to a Simscape™ Multibody™ joint, it is received as a physical signal at port q.

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 Rotational Multibody Interface block connection to a Simscape Multibody joint.

Hard Stop Model

To avoid mechanical damage to an actuator when it is fully extended or fully retracted, an actuator typically displays nonlinear behavior when the piston approaches these limits. The Single-Acting Rotary 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 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 Stroke or piston initial displacement. Outside of this region, $$F_{HardStop}=0.$$

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

Block Schematics

The Double-Acting Rotary Actuator (IL) block comprises three Foundation Library blocks:

• Ideal Rotational Motion Sensor

• Rotational Hard Stop

• Rotational Mechanical Converter (IL)

Underlying Block Components

Leakage

Laminar leakage is not accounted for in the Double-Acting Rotary Actuator (IL) block. To include leakage in your simulation, set the Cross-sectional geometry parameter to Custom and connect ports A and B to ports A and B of a Laminar Leakage (IL) block.

Adding Leakage to the Simulation

Examples

Sequencing Circuit for Two Rotary Actuators

A sequencing circuit that is based on four check valves installed in the pressure and return lines of the second rotary actuator. The cracking pressure of the meter-in check valves is set high enough to prevent flow into rotary actuator 2 while rotary actuator 1 is rotating, but lower than the pressure that develops once rotary actuator 1 reaches its hard stop. As a result, rotary actuator 2 starts moving only after rotary actuator 1 completes its stroke.

• Open Model

Ports

Input

q — Shaft angle

physical signal

Shaft angle, received as a physical signal from a Simscape Multibody block.

Dependencies

To expose this port, set Shaft rotation from chamber A to Provide input signal from Multibody joint.

Output

q — Actuator angle

physical signal

Physical signal output port associated with the shaft angular position.

Dependencies

To expose this port, set Shaft rotation from chamber A to Calculate from angular velocity of port R relative to port C.

Conserving

A — Chamber A inlet

isothermal liquid

Isothermal liquid conserving port associated with the actuator chamber A.

B — Chamber B inlet

isothermal liquid

Isothermal liquid conserving port associated with the actuator chamber B.

R — Actuator shaft

mechanical rotational

Mechanical rotational conserving port associated with the shaft.

C — Actuator casing

mechanical rotational

Mechanical rotational conserving port associated with the cylinder case.

Parameters

Actuator

Same fluid on both sides — Option to model same fluid in both chambers

on (default) | off

Whether to model the same fluid in both actuator chambers. If you select this parameter, the actuator propagates fluid properties through both chambers. Clear this parameter to model each chamber as a different fluid, where each chamber is connected to an isolated fluid network.

Mechanical orientation — Piston displacement direction

Pressure at A causes positive displacement of R relative to C (default) | Pressure at A causes negative displacement of R relative to C

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.

Volume displacement in chamber A — Volume displacement

1e-4 m^3/rad (default) | positive scalar

Effective displacement of the actuator in chamber A.

Volume displacement in chamber B — Volume displacement

1e-4 m^3/rad (default) | positive scalar

Effective displacement of the actuator in chamber B.

Stroke — Angle

5.0 rad (default) | positive scalar

Shaft maximum travel between stops.

Dead volume in chamber A — Fluid volume

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

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

Dead volume in chamber B — Fluid volume

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

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

Environment pressure specification — Pressure reference source

Atmospheric pressure (default) | Specified pressure

Choice of environment pressure. Options include Atmospheric pressure and Specified pressure.

Environment pressure — User-defined pressure reference

0.101325 MPa (default) | positive scalar

Pressure outside the actuator casing. This pressure acts against the pressures inside the actuator chambers. A value of zero corresponds to a vacuum.

Dependencies

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

Hard Stop

Hard stop model — Select the hard stop model

Stiffness and damping applied smoothly through transition region, damped rebound (default) | Full stiffness and damping applied at bounds, undamped rebound | Full stiffness and damping applied at bounds, damped rebound | Based on coefficient of restitution

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

Hard stop stiffness coefficient — Stiffness coefficient

1e6 N*m/rad (default) | positive scalar

Specifies the elastic property of colliding bodies for the Rotational Hard Stop block. The greater the value of the parameter, the more rigid the impact between the piston and the stop becomes. Lower values make contact softer and generally improve convergence and computational efficiency.

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

Hard stop damping coefficient — Damping coefficient

150 N*m(rad/s) (default) | positive scalar

Specifies the dissipating property of colliding bodies for the Rotational Hard Stop block. At zero damping, the impact is elastic. The greater the value of the parameter, the greater the energy dissipation during piston-stop interaction. Damping affects slider motion as long as the slider is in contact with the stop, including the period when slider is pulled back from the contact. Set this parameter to a nonzero value to improve the efficiency and convergence of your simulation.

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

Transition region — Transition region

0.001 rad (default) | positive scalar

Distance below which scaling is applied to the hard-stop force. The contact force is zero when the distance to the hard stop is equal to the value of this parameter. The contact force is at its full value when the distance to the hard stop is zero.

Dependencies

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

Coefficient of restitution — Ratio of final-to-initial relative speed between slider and stop after collision

0.7 (default) | unitless value between 0 and 1

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.

Static contact speed threshold — Threshold relative speed between slider and stop before collision

0.1 rad/s (default) | nonnegative scalar

Threshold relative speed between the 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.

Static contact release torque threshold — Threshold torque needed to transition from contact mode to free mode

0.001 N*m (default) | positive scalar

Minimum torque 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.

Initial Conditions

Shaft rotation from chamber A — Method for determining shaft angle

Calculate from velocity of port R relative to port C (default) | Provide input signal from Multibody joint

Method for determining the shaft angle. The block can receive the angle from a Multibody block when set to Provide input signal from Multibody joint, or calculates the angle internally, which is reported at port q.

Initial shaft rotation from chamber A — Initial rotation

0 rad (default) | scalar

The position of the actuator at the beginning of simulation. This value falls between 0 and the value of the Stroke in the positive orientation, and 0 and the negative value of the Stroke in the negative orientation.

Dependencies

To enable this parameter, set Shaft rotation from chamber A to Calculate from velocity of port R relative to port C.

Fluid dynamic compressibility — Fluid compressibility

On (default) | Off

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 liquid pressure in chamber A — Liquid pressure

0.101325 MPa (default) | positive scalar

Pressure in actuator chamber A at the start of simulation.

Dependencies

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

Initial liquid pressure in chamber B — Liquid pressure

0.101325 MPa (default) | positive scalar

Pressure in actuator chamber B at the start of simulation.

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 R2020a

R2024a: Model different fluids on each side of the actuator

Clear the new Same fluid on both sides parameter to block the propagation of fluid properties and model each chamber as a different fluid connected to its own isolated fluid network.

R2023a: New hard stop parameterization option

The block has a new option for the Hard stop model parameter. This option, called Based on coefficient of restitution, models the hard stop by using a mode chart.