The control signal feeds into the u port of the Frequency Response Estimator block. The u
- Δu port feeds into the plant input. Before you begin the estimation process, the block
feeds the control signal directly from u to u + Δu without adding any perturbation. In
that state, the block has no effect on the system behavior. (You can perform frequency
response estimation in an open-loop configuration by connecting u to a constant source
that drives your plant to the desired operating point for estimation. However, it is a good
practice to use the closed-loop configuration, particularly for real-time estimation. In a
closed-loop configuration, the controller works to suppress the injected disturbance and
maintain safe plant operation.)
The start/stop signal controls when the estimation process begins and ends (see “Step 2.
Configure Start/Stop Signal” on page 6-8). Start the experiment when the plant is in
steady state at the desired operating point. When the start/stop signal is positive, the
block injects test signals at u + Δu and measures the response at y. The block calculates
the estimated frequency response and returns it at the frd port.
For an example, see “Online Frequency Response Estimation During Simulation” on page
6-19.
Apply Perturbation Signal Only
The default configuration requires inserting the block between the controller and the
plant. If you want to add the perturbation signal to the control signal yourself, in the
Frequency Response Estimator block parameters, set Output Signal Configuration to
Online Estimation Using Plant Modeled in Simulink