LMIs in Control/pages/Discrete Time Bounded Real Lemma

Discrete-Time Bounded Real Lemma

A discrete time system operates on a discrete time signal input and produces a discrete time signal output. They are used in digital signal processing, such as digital filters for images or sound. The class of discrete time systems that are both linear and time invariant, known as discrete time LTI systems.

Discrete-Time Bounded Real Lemma or the H∞ norm can be found by solving a LMI.

The System

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Discrete-Time LTI System with state space realization  
 

The Data

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The matrices: System  .

The Optimization Problem

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The following feasibility problem should be optimized:

  is minimized while obeying the LMI constraints.

The LMI:

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Discrete-Time Bounded Real Lemma

The LMI formulation

H∞ norm <  

 

Conclusion:

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The H∞ norm is the minimum value of  that satisfies the LMI condition. If   is the minimal realization then the inequalities can be non-strict.

Implementation

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A link to CodeOcean or other online implementation of the LMI
MATLAB Code

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[1] - Continuous time KYP_Lemma_(Bounded_Real_Lemma)

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A list of references documenting and validating the LMI.


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