Prediction (slow->fast)

Prevent accuracy loss when connecting fixed-step networks with different step sizes

Since R2022a

• 

Libraries:
Simscape / Utilities / Network Couplers / Fundamental Components

Description

Note

Prediction and smoothing algorithms are built into the Network Coupler blocks, and you can enable them by using the check boxes in the block dialogs. The prediction and smoothing blocks in the Fundamental Components sublibrary are provided for your reference only.

Connecting a network with faster sampling (Network 1) to a network with slower sampling (Network 2) may result in accuracy loss in the Network 1 simulation when its sample times are between the sample times of Network 2. The Prediction (slow->fast) block helps prevent the accuracy loss. It predicts the output of Network 2 between its sample times by using the last computed derivative of the output of Network 2. The block implementation is a masked subsystem.

The subsystem contains blocks that run at both the slower and the faster rate. The Delay block is driven by the slower rate, and changes in its output are used as a trigger, so that the triggered subsystem captures the latest derivative of input u. The discrete-time integrator runs at the faster rate and uses this derivative to predict the output y until the next trigger event happens.

Ports

Input

u — Signal with slower sampling

real scalar

Connect this port to the slower network, Network 2, to capture its output.

Output

y — Prediction for the faster network

real scalar

Connect this port to the input of the faster network, Network 1.

Parameters

Port u discrete sample time (s) — Specify sample time for the slower network

-1 (default) | positive scalar

Specify sample time for the slower network, Network 2, in seconds.

Port y discrete sample time (s) — Specify sample time for the faster network

-1 (default) | positive scalar

Specify sample time for the faster network, Network 1, in seconds.

Extended Capabilities

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

Version History

Introduced in R2022a

R2024a: Support arrays of electrical nodes

To support arrays of electrical nodes and three-phase connections, the trigger logic has been updated. Previously, just a change in the first element of input u triggered a prediction cycle. Now, a change in any of the inputs triggers a prediction cycle. As a result, the two selector (U->Y) blocks added in R2023b have been removed.

For battery models with arrays of thermal nodes, the simulation results are the same as in previous releases. However, for models where the elements of the array of nodes are not physically coupled, this change can lead to a change in the trigger logic and therefore to a slight difference in simulation results.

R2023b: Support arrays of thermal nodes

To support arrays of thermal nodes, needed for the Network Coupler (Thermal Mass) block, two selector (U->Y) blocks have been added to the Prediction (slow->fast) block diagram, to keep the triggering signal scalar.

This change has no compatibility impact. If you open an existing model, the simulation results are the same as in previous releases.