Overview

Robust Control Toolbox software provides tools to model uncertainty in Simulink^®. Using these tools, you can analyze how the uncertainty impacts the time- and frequency-domain behavior of the Simulink model.

The Uncertain State Space block, included in the Robust Control Toolbox block library, is a convenient way to incorporate uncertainty information in a Simulink model. For more information, see Specifying Uncertainty Using Uncertain State Space Blocks. Using this block, you can perform the following types of analysis:

• Vary the uncertainty and see how it affects the time responses (Monte Carlo analysis). See Simulating Uncertainty Effects.

• Analyze the effects of uncertainty on the linearized dynamics:

  • If the operating point does not depend on the parameter uncertainty, use ulinearize to obtain an uncertain state-space model. You can then use usample to sample the uncertain variables and obtain a family of LTI models.

  • If the operating point depends on the parameter uncertainty, use usample to sample the uncertainty and then use the Simulink Control Design™ linearize command to compute the linearized dynamics for each uncertainty value.

    See How to Vary Uncertainty Values and Working with Models Containing Uncertain State Space Blocks.

• Compute an uncertain linearization, i.e., obtain an uncertain state space model (uss object) that combines the uncertain variables with the linearized dynamics. You can use this model to perform worst-case robustness analysis. See Working with Models Containing Uncertain State Space Blocks.

If you cannot use Uncertain State Space blocks in the Simulink model because you share the model or generate code, you can still compute an uncertain linearization by specifying a block to linearize to an uncertain variable. For example, you can specify a gain block to linearize to an uncertain real parameter (ureal). See Working with Models Containing Core Simulink or Custom Blocks. You can then use the uncertain state-space model to analyze robustness in the linear operating range.

Analyzing Uncertainty Effects in Simulink

Robust Control Toolbox Block Library

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