Gain margin issues of the two-stage and single-stage LQ reliable controls

This paper considers the gain margin issues, i.e., the stability gain margins (SGM) and the performance gain margins (PGM), of the recently proposed modified LQ reliable controls, i.e., the MTSLQRC and the SSLQRC. A new modified unified gain margin constraint is proposed to facilitate the discussions. It is shown that the SGM of the MTSLQRC is much larger than that of the SSLQRC while the PGM of the former is otherwise almost the same as that of the latter. An illustrative example is given to demonstrate the proposed results.