C2DelZOH:

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   Create a discrete time systems using the delta operator.

   Given
   .
   x = ax + bu

   Find f and g where

   x(k+1) = x + fx(k) + gu(k)

   Since version 1.
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   Form:
   [f, g] = C2DelZOH( a, b, T )
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   Inputs
   ------
   a            (n,n)  Continuous plant matrix
   b            (n,m)  Input matrix
   T            (1,1)  Time step

   -------
   Outputs
   -------
   f            (n,n)  Discrete plant matrix
   g            (n,m)  Discrete input matrix

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   References:  Van Loan, C.F., Computing Integrals Involving the Matrix
                Exponential, IEEE Transactions on Automatic Control
                Vol. AC-23, No. 3, June 1978, pp. 395-404.

                Middleton, R.H. and G.C. Goodwin, Digital Control and
                Estimation: A Unified Approach, Prentice-Hall, 1986
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