perturbation only. In this configuration, the block output contains the perturbation
signal only, at the port Δu. You inject this perturbation signal into the plant using, for
example, a sum block, as in the following diagram.In this configuration, because the Frequency Response Estimator is not part of the closed
loop, you can optionally comment it out without disrupting the loop configuration.Step 2. Configure Start/Stop Signal
To start and stop the frequency response estimation experiment, use a signal at the start/
stop port. When the experiment is not running, the block generates no perturbation
signal. In this state, the block has no impact on plant behavior. The frequency-response
estimation experiment begins and ends when the block receives a rising or falling signal
at the start/stop port, respectively. In the systems illustrated in “Step 1. Incorporate
Frequency Response Estimator into Model” on page 6-6, staggered step signals start and
stop the experiment. You can configure any other logic appropriate for your application to
control the start and stop times of the experiment. For example, you can use a Signal
Builder to configure a start/stop signal to carry out multiple experiments in a single
simulation run.6 Online Frequency Response Estimation