allmargin (Control System Toolbox)

Compute all crossover frequencies and corresponding stability margins

Syntax

```
S = allmargin(sys)
```

Description

allmargin computes the gain, phase, and delay margins and the corresponding crossover frequencies of the SISO open-loop model sys. allmargin is applicable to any SISO model, including models with delays.

The output S is a structure with the following fields:

GMFrequency -- All -180 degree crossover frequencies (in rad/sec)
GainMargin -- Corresponding gain margins, defined as 1/G where G is the gain at crossover
PMFrequency -- All 0 dB crossover frequencies in rad/sec
PhaseMargin -- Corresponding phase margins in degrees
DMFrequency and DelayMargin -- Critical frequencies and the corresponding delay margins. Delay margins are given in seconds for continuous-time systems and multiples of the sample time for discrete-time systems.
Stable -- 1 if the nominal closed-loop system is stable, 0 otherwise.

In general, stability cannot be assessed for FRD system. In any case when stability cannot be assessed, S is set to NaN.

See Also
ltimodels Help on LTI models

ltiview LTI system viewer

margin Gain and phase margins for SISO open-loop systems

acker append