Desired Loop Gain
Use this section of the dialog box to specify the target minimum loop gain.
- Pure integrator K/s
Check to specify a pure integrator shape for the target minimum loop gain. The
software chooses the integrator constant, K, based on the values you specify for a
target minimum gain and frequency. For example, to specify an integral gain profile
with crossover frequency 10 rad/s, enter 1 in the Choose K to keep gain above text
box. Then, enter 10 in the at the frequency text box. The software chooses the
integrator constant such that the minimum loop gain is 1 at 10 rad/s.- Other gain profile
Check to specify the minimum gain profile as a function of frequency. Enter a SISO
numeric LTI model whose magnitude represents the desired gain profile. For example,
you can specify a smooth transfer function (tf, zpk, or ss model). Alternatively, you
can sketch a piecewise target loop gain using an frd model. When you do so, the
software automatically maps the profile to a smooth transfer function that
approximates the desired minimum loop gain. For example, to specify minimum gain
of 100 (40 dB) below 0.1 rad/s, rolling off at a rate of –20 dB/dec at higher frequencies,
enter frd([100 100 10],[0 1e-1 1]).If you are tuning in discrete time, you can specify the minimum gain profile as a
discrete-time model with the same sampling time as you use for tuning. If you specify
the gain profile in continuous time, the tuning software discretizes it. Specifying the
profile in discrete time gives you more control over the profile near the Nyquist
frequency.Options
Use this section of the dialog box to specify additional characteristics of the minimum
loop gain goal.
- Enforce goal in frequency range
Limit the enforcement of the tuning goal to a particular frequency band. Specify the
frequency band as a row vector of the form [min,max], expressed in frequency units
of your model. For example, to create a tuning goal that applies only between 1 and
100 rad/s, enter [1,100]. By default, the tuning goal applies at all frequencies for
continuous time, and up to the Nyquist frequency for discrete time.Minimum Loop Gain Goal