Desired Margins
Use this section of the dialog box to specify the minimum gain and phase margins for the
feedback loop.
- Gain margin (dB)
Enter the required minimum gain margin for the feedback loop as a scalar value
expressed in dB.- Phase margin (degrees)
Enter the required minimum phase margin for the feedback loop as a scalar value
expressed in degrees.For MIMO feedback loops, the gain and phase margins are based on the notion of disk
margins, which guarantee stability for concurrent gain and phase variations in all
feedback channels. For information about multiloop disk margins, see “Stability Analysis
Using Disk Margins” (Robust Control Toolbox).
Options
Use this section of the dialog box to specify additional characteristics of the stability
margin 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.For best results with stability margin requirements, pick a frequency band extending
about one decade on each side of the gain crossover frequencies.- D scaling order
This value controls the order (number of states) of the scalings involved in computing
MIMO stability margins. Static scalings (scaling order 0) are used by default.
Increasing the order may improve results at the expense of increased computations. If
the stability margin plot shows a large gap between the optimized and actual margins,Margins Goal