National Instruments 370757C-01 用户手册

factor by which the RMS value of a signal flowing through H can be 
increased. 

By comparison, the H

 norm is defined as:

This norm can be interpreted as the RMS value of the output when the input 
is unit intensity white noise. It can be computed in Xmath using the 

rms( )

 

function.

For discrete-time systems with a stable H,

where   is the maximum singular value and H(e

ω

) is the transfer matrix 

under consideration.

[sigma, vOMEGA] = linfnorm( Sys, {tol,maxiter} )

The 

linfnorm( )

 function computes the L

∞

 norm of a dynamic system 

using a quadratically convergent algorithm. The 

linfnorm( )

 function 

relies on eigenvalue calculations of a Hamiltonian matrix with twice as 
many states as 

Sys

 and, consequently, may be unreliable for large systems. 

A singular value plot created with 

svplot( )

can be used as an alternative 

in these cases. Refer to the 

 section.

•

The keyword 

tol

 controls the required relative accuracy. The default 

is 0.01. 

maxiter

 is the maximum number of iterations. The default 

is 15.

•

If the maximum norm is found at 

ω = ∞, 

linfnorm( )

 returns:

2

1

2

π

------

σ

ω

( )

(

)

2

1

=

∑

∞

–

∞

∫

=

∞

ω

π π

,

–

(

)

∈

σ H e

ω

(

)

(

)

=

σ