PILeaky:

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   Design a PI controller of the form

   y =  cx + du
   x =  ax + bu

   The transfer function is

   K ( 1 +    1     ) 
           --------
           tau(s+a)

   The inputs are gain at zero, gain at infinity and 0 dB crossover frequency.
   If the gain at zero frequency is not infinity you get a "leaky" integrator.
   Leaky integrators can give you sufficient gain a DC for your application
   with giving you the stability problems of regular integrators.

   With one output, the routine will give you the conventional statespace
   form [a, b, c, d]. With one output you will get an object of the statespace
   class.

   If the gain at infinity is greater than 1, w0Db is the corner frequency.

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   Form:
   [g, b, c, d] = PILeaky( k0, kInf, w0Db, tSamp, sType )
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   ------
   Inputs
   ------
   k0                  Gain at zero (may be inf) (dB)
   k                   Gain at infinity (forward gain) (dB)
   w0Db                0 db crossover (rad/sec)
   tSamp               Sampling period (sec)
   sType               State equation type ('Delta' or 'Z')

   -------
   Outputs
   -------
   g                   Statespace data structure or
   [g, b, c, d]        Statespace

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Children:

Common: Classes/@statespace/statespace.m
Common: Control/C2DZOH
Common: Control/C2DelZOH
Common: Control/FResp