Recently, a \textbf{ SCHUR} method was proposed in \cite{ Chu2} to solve the robust pole assignment problem in state feedback control. It takes the departure from normality of the closed-loop system matrix $A_c$ as the measure of robustness, and intends to minimize it via the real Schur form of $A_c$. The \textbf{ SCHUR} method works well for real poles, but when complex conjugate poles are involved, it does not produce the real Schur form of $A_c$ and can be problematic. In this paper, we put forward a modified Schur method, which improves the efficiency of \textbf{ SCHUR} when complex conjugate poles are to be assigned. Besides producing the real Schur form of $A_c$, our approach also leads to a relatively small departure from normality of $A_c$. Numerical examples show that our modified method produces better or at least comparable results than both \textbf{ place} and \textbf{ robpole} algorithms, with much less computational costs.
Categories: math.OC