A modified Schur method for robust pole assignment in state feedback control

Recently, a SCHUR method was proposed in Chu (2007) to solve the robust pole assignment problem in state feedback control. It takes the departure from normality of the closed-loop system matrix AcAc as the measure of robustness, and intends to minimize it via the real Schur form of AcAc. The SCHUR method works well for real poles, but when complex conjugate poles are involved, it does not produce the real Schur form of AcAc and can be problematic. In this paper, we propose a modified Schur method, which improves SCHUR when nonreal poles are to be assigned. Besides producing the real Schur form of AcAc, our approach also leads to a relatively small departure from normality of AcAc. Numerical examples show that our modified method produces better or at least comparable results than both place and robpole algorithms, with much less computational costs.