Internal stabilization and decoupling in linear multivariable systems by unity output feedback compensation

We consider the problem of internally stabilizing and simultaneously diagonally decoupling a linear multivariable system by unity output feedback compensation. A sufficient condition is derived for the existence of a cascade proper compensator
C(s)
such that when employed in a unity feedback loop involving the proper transfer function matrix P
o
of a free of unstable hidden modes system
\Sigma(P_{o})
, will not only internally stabilize the feedback closed-loop system
\Sigma(P_{o}, C)
but will also give rise to a closed-loop transfer function matrix
H_{yr}^{diag}
, which is nonsingular, diagonal, and has desired poles. Based on this analysis, an algorithmic procedure for the computation of such a compensator is presented.