robOptions
Option set for robustness analysis
Description
Examples
Options for Robustness Margin Calculation
Create an options set for a robstab
, robgain
, or musynperf
calculation that displays the progress of the underlying mussv
calculation. Also, turn on the element-by-element sensitivity calculation.
opts = robOptions('Display','on','Sensitivity','on');
Alternatively, create a default option set, and use dot notation to set the values of particular options.
opts = robOptions; opts.Display = 'on'; opts.Sensitivity = 'on';
Use opts
as an input argument to robstab
, robgain
, or musynperf
.
Input Arguments
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: 'Display','on','Sensitivity','on'
Display
— Display progress of computation and summary report
'off'
(default) | 'on'
Display progress and summary of the robustness computation,
specified as the comma-separated pair consisting of 'Display'
and
one of these values:
'off'
— Do not display progress and report.'on'
— Display progress and report. When you use this option, a progress indicator and summary of results is displayed in the command window, similar to the following.points completed (of 28) ... 28 System is robustly stable for the modeled uncertainty. -- It can tolerate up to 116% of the modeled uncertainty. -- There is a destabilizing perturbation amounting to 117% of the modeled uncertainty. -- This perturbation causes an instability at the frequency 5.9 rad/seconds.
This setting overrides the silent ('s'
)
option in the MussvOptions
option.
VaryFrequency
— Compute robustness margin as function of frequency
'off'
(default) | 'on'
Return robustness margin as a function of frequency, specified
as the comma-separated pair consisting of 'VaryFrequency'
and
one of these values:
'off'
— Only return margins at frequencies where robustness is weakest.'on'
— Compute robustness margins over a frequency grid suitable for plotting. The frequency grid is chosen automatically based on system dynamics. This calculation is done in addition to identifying the critical frequency where the margin is weakest. Access the frequency values and corresponding margins in theinfo
output ofrobstab
androbgain
.
This option is ignored for ufrd
and genfrd
models.
Sensitivity
— Calculate sensitivity of robustness margin
'off'
(default) | 'on'
Calculate the sensitivity of the robustness margin to each uncertain
element in the model, specified as the comma-separated pair consisting
of 'Sensitivity'
and either 'off'
or 'on'
.
Each uncertain element contributes to the overall stability
margin in a coupled manner. Set this option to 'on'
to
estimate the sensitivity of the margin to each element. This element-by-element
sensitivity provides an indication of which elements are most problematic
for robustness. Access the sensitivity estimates in the info
output
of robstab
and robgain
.
SensitivityPercent
— Percentage variation of uncertainty for computing sensitivity
25 (default) | positive scalar value
Percentage variation of uncertainty level for computing sensitivity,
specified as the comma-separated pair consisting of 'SensitivityPercent'
and
a positive scalar value. The sensitivity to a particular uncertain
element is estimated using a finite difference calculation. This calculation
increases the (normalized) amount of uncertainty on this element by
some percentage, computes the resulting robustness, and computes the
ratio of percent variations. This option specifies the percentage
increase in uncertainty level applied to each element. The default
value is 25%.
MussvOptions
— Options for mussv
calculation
''
(default) | character vector
Options for the underlying mussv
calculation
that robstab
and robgain
perform,
specified as the comma-separated pair consisting of 'MussvOptions'
and
a character vector such as 'sm3'
or 'ad'
.
Some MussvOptions
values that are especially
useful for improving robustness-margin calculations include:
'a'
— Force the use of LMI optimization to compute the μ upper bound, which yields better results in general but can be expensive when someureal
elements are repeated multiple times.'mN'
— Use multiple restarts when computing the μ lower bound, which corresponds to the upper bound for robustness margins. This option can reduce the gap between the lower bound and upper bound on the robustness margins.N
is the number of restarts. For example, setting'MussvOptions'
to'm3'
causes three restarts.
See mussv
for the remaining
available options and corresponding characters. The default, ''
,
uses the default options for mussv
.
Output Arguments
opts
— Options for robustness commands
robOptions
object
Options for robustness commands robstab
, robgain
,
and musynperf
, returned as a
robOptions
object. Use the options as
an input argument to robstab
,
robgain
, or
musynperf
. For example:
[stabmarg,wcu,info] = robstab(usys,opts)
Version History
Introduced in R2016bR2016b: robOptions
replaces robustperfOptions
and
robuststabOptions
robOptions
replaces
robustperfOptions
and
robuststabOptions
, which are no longer
recommended.
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