ufind

Find uncertain variables in Simulink model

Syntax

uvars = ufind(mdl)

[uvars,pathinfo] = ufind(mdl)

uvars = ufind(usys1,...,usysN)

Description

uvars = ufind(mdl) finds Uncertain State Space blocks in the Simulink^® model mdl. The function returns a structure containing all uncertain variables associated with the Uncertain State Space blocks. These uncertain variables are the ureal, umargin, or ultidyn elements in the uss model specified in the Uncertain system variable parameters of the blocks.

ufind finds Uncertain State Space blocks inside masked subsystems, library links, and model references. However, the function does not find blocks inside accelerated model references.

[uvars,pathinfo] = ufind(mdl) returns paths to each Uncertain State Space block in mdl and the corresponding uncertain variables referenced by the block. You can use this information to verify that all Uncertain State Space blocks have been identified.

uvars = ufind(usys1,...,usysN) collects uncertain variables referenced by the uncertain dynamic system models usys1,…,usysN, which can be uss or ufrd models. You can use this syntax as a faster alternative to querying the Simulink model, when you know the uncertain models referenced by its Uncertain State Space blocks.

Examples

Find Uncertain Variables in a Model

Find all Uncertain State Space blocks and uncertain variables in a Simulink® model. First, open the model.

mdl = "usim_model";
open_system(mdl)

The model contains three Uncertain State Space blocks named Unmodeled Plant Dynamics, Plant, and Sensor Gain. These blocks are predefined to depend on three uncertain variables named input_unc, unc_pole and sensor_gain. Use ufind to find all these uncertain variables in the model and gather them into a data structure.

[uvars,pathinfo] = ufind(mdl);

Examine the structure uvars. Each uncertain variable is a ureal or ultidyn uncertain element and is listed by name in uvars.

uvars

uvars = struct with fields:
      input_unc: [1x1 ultidyn]
    sensor_gain: [1x1 ureal]
       unc_pole: [1x1 ureal]

You can use uvars for analysis of the responses of the uncertain system. For instance, you can use it as an argument to usample to simulate the model at random values of all the uncertain variables, as shown in Vary Uncertain Values Across Multiple Uncertain Blocks.

If you need a list of the block paths that contain uncertain variables, use the pathinfo output argument. pathinfo is a two-column cell array. The first column lists the paths to each Uncertain State Space block in the model. The second column lists the uncertain elements associated with the corresponding block.

pathinfo

pathinfo = 3x2 cell
    {'usim_model/Plant'                   }    {'unc_pole'   }
    {'usim_model/Sensor Gain'             }    {'sensor_gain'}
    {'usim_model/Unmodeled Plant Dynamics'}    {'input_unc'  }

Input Arguments

mdl — Simulink model name

string | character vector

Simulink model name, specified as a string or a character vector.

If the same uncertain variable name has different definitions in mdl, the function returns an error. For example, if your model contains two Uncertain State Space blocks, one referencing a variable 'unc_par' with value ultidyn('unc_par',[1 1]) and another referencing 'unc_par' with value ureal('unc_par',5), an error occurs.

Example: "usim_model", 'usim_model'

usys — Uncertain dynamic system model

uss model object | ufrd model object

Uncertain dynamic system model, specified as a uss model object or a ufrd model object.

Output Arguments

uvars — Uncertain variables in model

structure

Uncertain variables in the input model, returned as a structure whose fields are the names of the uncertain variables in the model and whose values are the uncertain elements. These uncertain variables are:

• The uncertain elements in any uss or ufrd models referenced in the Uncertain State Space blocks in the Simulink model specified by mdl.

• The uncertain elements in the uss or ufrd models specified by usys1,…,usysN.

pathinfo — Paths to blocks referencing uncertain variables

two-column cell array

Paths to blocks referencing uncertain variables, returned as a two-column cell array. The first column lists the paths to each Uncertain State Space block in the model, specified as character vectors. The second column lists the uncertain variables associated with the corresponding Uncertain State Space block, also specified as character vectors.

Version History

Introduced in R2009b