Network Coupler (Compressible Link)

Split network at a mechanical translational connection

Since R2022a

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Libraries:
Simscape / Utilities / Network Couplers

Description

The Network Coupler (Compressible Link) block provides a starting point for you to split a Simscape™ network into two coupled networks at a mechanical translational connection.

The Network Coupler (Compressible Link) block works by adding a compliance between the two networks. It is assumed that there is a mass on either side of the coupler block. Do not connect the block ports directly to a force source. You can connect the block ports to an ideal translational velocity source.

If your model has an existing compressible link (modeled as a Translational Spring block connected in parallel with a Translational Damper block), then use the Network Coupler (Compressible Link) block to directly replace these two blocks. This avoids adding a second compliance with which to separate the network. If there is no existing model compliance that you can use, then add a numeric one by inserting the Network Coupler (Compressible Link) block at a mechanical translational connection and setting its Separate using parameter to an added numerical compliance.

Working with the Block on the Model Canvas

When you add the block to your model and double-click it, the Network Coupler (Compressible Link) subsystem opens.

The Port 1 Interface block contains the dynamics that break the algebraic loop. Double-click this block to set all of the Network Coupler (Compressible Link) subsystem parameters and view the derived values.

The rate transition blocks are, by default, commented through. Uncomment them if at least one of the coupled networks is running fixed step.

Using the Derived Values to Estimate Block Parameters

On the Analysis tab of the Port 1 Interface block dialog box, the Derived values section contains a list of recommended values that you can use when specifying block parameters. For example, use the Recommended max discrete sample time (s) derived value to verify that your Port 1 network discrete sample time (s) and Port 2 network discrete sample time (s) parameter values are within acceptable limits.

The derived values list is based on the chosen block configuration. For example:

• If you are using an existing compliance, the block uses information about the masses of the connected networks, plus the compliance, to recommend either a maximum filter time constant, or a maximum discrete sample time. To do this, the block calculates overall network dynamic time constants and recommends the time constant (Recommended max filter time constant (s)) or sample time (Recommended max discrete sample time (s)) values that are commensurate with the fastest time constant.

• If you are adding a numeric compliance, the block calculates the stiffness and damping required, based on the connected network masses and the specified sample time or filter time constant. It also provides an estimate of the fastest trackable time constant. If the Calculated fastest trackable time constant (s) value is too slow for your application, then you must reduce the value you specified for the relevant block parameter, such as Separator time constant (s), Port 1 network discrete sample time (s), or Port 2 network discrete sample time (s).

The Update button lets you recalculate the derived values after you change the parameters of the connected networks.

Ports

Conserving

1 — Connect this port to the variable-step network, or to the fixed-step network with the smaller sample time

mechanical translational

If one of the coupled networks is running variable step, connect it to port 1 of the Network Coupler (Compressible Link) block. If both networks are running fixed step, connect this port to the network with the smaller sample time. If both networks are running variable step, or fixed step with the same step size, then the block polarity does not matter.

2 — Connect this port to the fixed-step network with the larger sample time

mechanical translational

If one of the coupled networks is running variable step, connect port 2 of the Network Coupler (Compressible Link) block to the fixed-step network. If both networks are running fixed step, connect this port to the network with the larger sample time.

Parameters

Main

Separate using — Select separation type

an actual link compliance (default) | an added numerical compliance

Select how to separate the coupled networks:

• an actual link compliance — Split the network at a point where there is an actual compressible link (spring and damper). Use the shaft compliance to improve stability of the coupled networks.

• an added numerical compliance — Add a numerical compliance and use it to improve stability of the coupled networks.

Link stiffness (N/m) — Specify stiffness of compressible link

250 (default) | positive scalar

If you are replacing an actual spring and damper in the model, specify the spring rate. Use the Spring rate parameter value from the Translational Spring block being replaced, converting it to N/m, if necessary.

Dependencies

To enable this parameter, set the Separate using parameter to an actual link compliance.

Link damping (N/(m/s)) — Specify damping coefficient of compressible link

20 (default) | positive scalar

If you are replacing an actual spring and damper in the model, specify the damping coefficient. Use the Damping coefficient parameter value from the Translational Damper block being replaced, converting it to N/(m/s), if necessary.

Dependencies

To enable this parameter, set the Separate using parameter to an actual link compliance.

Sampling type — Select sampling types scenario for coupled networks

Variable step at ports 1 and 2 (default) | Variable step at port 1 and fixed step at port 2 | Fixed step both ports with common sample time | Fixed step both ports with faster sampling at port 1

Select how the coupled networks are sampled:

• Variable step at ports 1 and 2 — Both networks are variable-step.

• Variable step at port 1 and fixed step at port 2 — Network 1 is variable-step and Network 2 is fixed-step.

• Fixed step both ports with common sample time — Both networks are fixed-step, with the same step size.

• Fixed step both ports with faster sampling at port 1 — Both networks are fixed-step, with different step sizes.

Separator time constant (s) — Specify filter time constant

0.001 (default) | positive scalar

Specify the filter time constant, in seconds, to remove the algebraic loop.

Dependencies

To enable this parameter, set the Sampling type parameter to Variable step at ports 1 and 2.

Port 1 network discrete sample time (s) — Specify sample time for Network 1

0.001 (default) | positive scalar

Specify sample time for Network 1, in seconds.

Dependencies

To enable this parameter, set the Sampling type parameter to Fixed step both ports with common sample time or Fixed step both ports with faster sampling at port 1.

Port 2 network discrete sample time (s) — Specify sample time for Network 2

0.01 (default) | positive scalar

Specify sample time for Network 2, in seconds.

Dependencies

To enable this parameter, set the Sampling type parameter to Variable step at port 1 and fixed step at port 2 or Fixed step both ports with faster sampling at port 1.

Use prediction when connecting fixed step to variable step — Lets you enable the prediction (discrete->continuous) algorithm

off (default) | on

Select this check box to enable the prediction (discrete->continuous) algorithm. For more information, see Prediction and Smoothing.

Dependencies

To display this option, set the Sampling type parameter to Variable step at port 1 and fixed step at port 2.

Use smoothing when connecting variable step to fixed step — Lets you enable the smoothing (continuous->discrete) algorithm

off (default) | on

Select this check box to enable the smoothing (continuous->discrete) algorithm. For more information, see Prediction and Smoothing.

Dependencies

To display this option, set the Sampling type parameter to Variable step at port 1 and fixed step at port 2.

Smoothing time constant (s) — Specify time constant for the first-order filter

0.01 (default) | positive scalar

Specify time constant, in seconds, for the first-order filter that the smoothing algorithm uses to remove unwanted high-frequency information.

Dependencies

To enable this parameter, select the Use smoothing when connecting variable step to fixed step check box.

Use prediction when connecting slow to fast sample times — Lets you enable the prediction (slow->fast) algorithm

off (default) | on

Select this check box to enable the prediction (slow->fast) algorithm. For more information, see Prediction and Smoothing.

Dependencies

To display this option, set the Sampling type parameter to Fixed step both ports with faster sampling at port 1.

Use smoothing when connecting fast to slow sample times — Lets you enable the smoothing (fast->slow) algorithm

off (default) | on

Select this check box to enable the smoothing (fast->slow) algorithm. For more information, see Prediction and Smoothing.

Dependencies

To display this option, set the Sampling type parameter to Fixed step both ports with faster sampling at port 1.

Number of samples over which to smooth — Specify number of samples for averaging

1 (default) | positive scalar

The smoothing algorithm works by averaging the last N samples. You specify N by using this parameter.

Dependencies

To enable this parameter, select the Use smoothing when connecting fast to slow sample times check box.

Analysis

Approximate mass at port 1 (kg) — Specify approximate mass at port 1

1 (default) | positive scalar

Specify approximate mass at port 1, in kg.

Approximate mass at port 2 (kg) — Specify approximate mass at port 2

1 (default) | positive scalar

Specify approximate mass at port 2, in kg.

For information on how to use the Derived values section, see Using the Derived Values to Estimate Block Parameters.

Initial Conditions

Initial transmitted force (N) — Specify initial force transmitted by the link

0 (default) | positive scalar

Specify initial condition for the force transmitted by the link, in N.

Extended Capabilities

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

Version History

Introduced in R2022a