Simulink Control Design™ - MathWorks

Frequency Response Estimator

Estimate plant frequency responses during simulation or in real time

Library: Simulink Control Design

Description

Use the Frequency Response Estimator block to perform experiment-based estimation in

real time with a physical plant or in a Simulink model during simulation. To obtain an

estimated frequency response, the block simultaneously:

• Injects sinusoidal test signals into the plant at the nominal operating point


• Collects response data from the plant output


• Computes the estimated frequency response

You specify the frequencies at which to perturb the plant and measure system response.

You trigger the estimation process via a start/stop signal. This signal lets you start

estimation at any time, typically when the plant is at the nominal operating point. You

stop the estimation after the frequency responses converge.

You can use online frequency response estimation with any stable SISO plant. For an

unstable plant, online estimation works in a closed-loop configuration, provided that the

closed loop is internally stable. A closed-loop system is internally stable if and only if the

roots of the nominal closed-loop characteristic equation all lie in the open left half-plane.

For a plant with transfer function G = NG/DG and controller C = NC/DC, the characteristic

equation is:

DGDC + NGNC = 0.

In practice, this condition means that no unstable poles in G are stabilized by pole-zero

cancellation in GC. Do not use online estimation with an unstable plant that does not meet

this condition.

You can generate code and deploy the Frequency Response Estimator block on hardware

to perform the estimation in real time. The block supports code generation with Simulink

16 Blocks — Alphabetical List