usample

Generate random samples of uncertain variables in a Simulink model

Syntax

samples = usample(uvars,N)
samples = usample(uvars)
samples = usample(uvars,N,Wmax)

Description

This function is for generating random samples of uncertain variables stored in a data structure you obtain from a Simulink^® model, using ufind. To generate random samples from uncertain models (uss, ufrd) or generalized state-space models (genss, genfrd), use usample (uss).

samples = usample(uvars,N) generates N random samples of the uncertain variables in uvars. uvars is a structure that lists uncertain variables (ureal, ucomplex, umargin, or ultidyn) by name. You can automatically obtain uvars for a Simulink model that contains Uncertain State Space blocks using ufind. samples is an N-by-1 structure array whose field names and values are the names and sample values of the uncertain variables. Use this syntax, together with ufind, to generate random samples for uncertain variables in Simulink models.

samples = usample(uvars) is equivalent to usample(uvars,1).

samples = usample(uvars,N,Wmax) specifies constraints, as described in uss/usample, for sampling uncertain variables of type ultidyn in uvars.

Examples

collapse all

Generate Random Samples of Uncertain Variables

Open Live Script

Create a structure that contains uncertain variables a and b.

uvars = struct('a',ureal('a',5),'b',ultidyn('b',[2 3],'Bound',7))

uvars = struct with fields:
    a: [1x1 ureal]
    b: [2x3 ultidyn]

Generate a random sample of a and b.

samples = usample(uvars)

samples = struct with fields:
    a: 5.6294
    b: [2x3 ss]

samples is also a structure, where each field contains a randomly sampled instance of the uncertain variable type in uvars. You can use samples to simulate an uncertain Simulink model at these values as shown in Sample Uncertain Variables in a Simulink® Model.

Sample Uncertain Variables in a Simulink® Model

This example uses:

Open Script

Generate random samples of uncertain variables in a Simulink® model.

Open the model.

open_system('usim_model')

The model contains three Uncertain State Space blocks named Unmodeled Plant Dynamics, Plant, and Sensor Gain. These blocks depend on three uncertain variables named input_unc, unc_pole, and sensor_gain.

Use ufind to find all Uncertain State Space blocks and uncertain variables in the model.

uvars = ufind('usim_model');

Use usample to generate random samples of input_unc, unc_pole, and sensor_gain. Simulate the closed-loop response for each of these random samples.

for i=1:10;
   uval = usample(uvars);
    sim('usim_model',10);
end

The MultiPlot Graph block displays the simulated responses.

Tutorials

Simulate Uncertain Model at Sampled Parameter Values

Vary Uncertain Values Across Multiple Uncertain Blocks

Robustness Analysis in Simulink

How To

Simulate Uncertainty Effects

Documentation