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H_{∞} norm of dynamic system

`ninf = hinfnorm(sys)`

`ninf = hinfnorm(sys,tol)`

```
[ninf,fpeak]
= hinfnorm(___)
```

returns
the `ninf`

= hinfnorm(`sys`

)*H _{∞}* norm in absolute units of the dynamic
system model,

`sys`

. If

`sys`

is a stable SISO system, then the*H*norm is the peak gain, the largest value of the frequency response magnitude._{∞}If

`sys`

is a stable MIMO system, then the*H*norm is the largest singular value across frequencies._{∞}If

`sys`

is an unstable system, then the*H*norm is defined as_{∞}`Inf`

.If

`sys`

is a model that has tunable or uncertain parameters, then`hinfnorm`

evaluates the*H*norm at the current or nominal value of_{∞}`sys`

.If is a model array, then

`hinfnorm`

returns an array of the same size as`sys`

, where`ninf(k) = hinfnorm(sys(:,:,k))`

.

For stable systems, `hinfnorm(sys)`

is the
same as `getPeakGain(sys)`

.

`freqresp`

| `getPeakGain`

| `norm`

| `sigma`