wrong results for d2c in control toolbox

[Chris Eddington]

Hi,

I'm  comparing the d2c and c2d functions in the control toolbox to some 
matlab examples in a textbook.  The following commands:

sysd = tf2sys([0 -2 1],[1 -2 1],1);
sysc = d2c(sysd,1e-24);
syscd = c2d(sysc,1e-24);
[numd dend] = sys2tf(sysd)
[numc denc] = sys2tf(sysc)
[numcd, dencd] = sys2tf(syscd)

should return [numc,denc] =  [0 -1.5 -1]   /  [1 0 0]  and numcd = numd 
and dencd = dend.

Instead I get numc = 0 -1.45 -0.6244  and denc = 1  -0.27 0.08.
and numcd , dencd do not match original.

Anyone  get this to work correctly or any ideas what might be wrong?

Thks,
Chris



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