Configure Experiment Settings
In the Experiment Settings section, you specify parameters that control the frequency-
response estimation experiment. For more details about these settings, click Help.1 Specify whether to run two simulations (default) or one. If your model includes
disturbances that can affect the result of the frequency-response estimation
experiment, select 2 simulations (remove disturbances). With this option
selected, the tuner runs a baseline simulation and substracts the resulting frequency
response from the perturbed simulation to remove the effects of disturbances. If your
model does not include any such disturbances, skip the baseline simulation by
selecting 1 simulation.(^2) Specify whether the plant is asymptotically stable or has a single integrator. If the
plant is asymptotically stable, the estimation experiment includes an estimation of
the plant DC gain. The Frequency Response Based PID Tuner performs this
estimation by injecting a step signal into the plant.
CautionDo not use the Frequency Response Based PID Tuner with an unstable
plant or a plant containing multiple integrators.
(^3) Specify the start time of the experiment in the Start time (t0) field. Start the
experiment when the plant is at the desired equilibrium operating point. For
instance, if you know that your simulation must run to 10 s for the plant to reach
such an operating point, specify a start time of 10.
(^4) Specify the experiment duration in the Duration (tspan) field. Let the experiment
run long enough for the frequency-response estimation algorithm to collect sufficient
data for a good estimate at all frequencies it probes. A conservative estimate for the
experiment duration is 100/ωc, where ωc is the target bandwidth for tuning that you
specify.
(^5) Specify the perturbation amplitudes. During the tuning experiment, the Frequency
Response Based PID Tuner injects a sinusoidal signal into the plant at four
frequencies, [1/3,1,3,10]ωc. Use the Sine amplitudes (Asin) field to specify the
amplitudes of these injected signals. You can provide a scalar value to inject the same
amplitude at each frequency, or a vector of length 4 to specify different amplitudes
for each.
In a typical plant with typical target bandwidth, the magnitudes of the plant
responses at the experiment frequencies do not vary widely. In such cases, you can
use a scalar value to apply the same magnitude perturbation at all frequencies.
7 PID Controller Tuning