Simulink Control Design™ - MathWorks

• Vector of length 4 to specify a different amplitude at each of [1/3, 1, 3, 10]ωc

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. However, if you know that

the response decays sharply over the frequency range, consider decreasing the amplitude

of the lower-frequency inputs and increasing the amplitude of the higher-frequency

inputs. It is numerically better for the estimation experiment when all the plant responses

have comparable magnitudes.

The perturbation amplitudes must be:

• Large enough that the perturbation overcomes any deadband in the plant actuator and
  generates a response above the noise level


• Small enough to keep the plant running within the approximately linear region near
  the nominal operating point, and to avoid saturating the plant input or output

In the experiment, the sinusoidal signals are superimposed (with the step perturbation, if

any, in the case of open-loop tuning). Thus, the perturbation can be at least as large as the

sum of all amplitudes. Therefore, to obtain appropriate values for the amplitudes,

consider:

• Actuator limits. Make sure that the largest possible perturbation is within the range of
  your plant actuator. Saturating the actuator can introduce errors into the estimated
  frequency response.


• How much the plant response changes in response to a given actuator input at the
  nominal operating point for tuning. For instance, suppose that you are tuning a PID
  controller used in engine-speed control. You have determined that at frequencies
  around the target bandwidth, a 1° change in throttle angle causes a change of about
  200 rpm in the engine speed. Suppose further that to preserve linear performance the
  speed must not deviate by more than 100 rpm from the nominal operating point. In
  this case, choose amplitudes to ensure that the perturbation signal is no greater than
  0.5 (assuming that value is within actuator limits).

To provide the sine amplitudes via an input port, select Use external source.

Tunable: Yes

Programmatic Use

Block Parameter: AmpSine

Type: scalar, vector of length 4

16 Blocks — Alphabetical List