Varying Lowpass Filter

R2026b

Butterworth filter with varying coefficients

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Varying Lowpass Filter block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Control System Toolbox / Linear Parameter Varying

Description

The block implements an analog N^th-order Butterworth filter with unit DC gain and varying cutoff frequency that you provide as an input to the block.

Use this block and the other blocks in the Linear Parameter Varying library to implement common control elements with variable parameters or coefficients. For more information, see Model Gain-Scheduled Control Systems in Simulink.

Caution

Avoid making the cutoff frequency depend on the block output y. If you have such dependence, the resulting filter causes an algebraic loop, because computing the block output value requires knowing the block output value. This algebraic loop is prone to instability and divergence.

Ports

Input

u — Filter input

scalar

Lowpass filter input signal.

freq — Cutoff frequency

scalar

Filter cutoff frequency, specified in rad/s.

Output

y — Filter output

scalar

Lowpass filter output signal.

Parameters

Filter order — Lowpass filter order

1 (default) | positive integer

Lowpass filter order, specified as a positive integer.

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"cstblocks/Linear Parameter Varying/Varying Lowpass Filter"

Example: add_block("cstblocks/Linear Parameter Varying/Varying Lowpass Filter","myModel/myBlock",MakeNameUnique="on")

Extended Capabilities

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

Version History

Introduced in R2017b