Comment on “Further Enhancement on Robust src='/images/tex/516.gif' alt='H_{infty }'> Control Design for Discrete-Time Singular Systems”

摘要

In the above paper, a robust control design method was presented for uncertain discrete-time singular systems, which was formulated in terms of bilinear matrix inequalities and claimed to be necessary and sufficient. In this note, it is shown that the necessity of Theorem 4 in the above paper and its consequences do not hold. Then, the robust control design method in the above paper is only sufficient. It is also noted here that conditions in the rest of the above paper are necessary and sufficient.