a Robust Control Problem

I have a robust control problem. I have a system with parametric uncertainty. I made its generalized plant with its uncertainty and performance
weighting functions by sysic command in matlab mu toolbox. But D matrix in the generalized plant becomes zero so I couldn't use "hinfsyn" or "dkit" for designing controller. What's the solution? Any help would be appreciated .
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It's probably well known numeric property of algorithm. Look at your weighting functions. If there is 1/s (in Performance function) make it 1/(s+0.00001), if there is improperness in revers Wi than make it proper. This solution is described more precisely in robust toolbox datasheet somewhere here http://www.mathworks.com/products/robust /.
--
Mikolaj

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