“…As a common descriptor system, the high-order descriptor linear system (HODLS) has a wide perspective of applications since many physical systems, including hydraulic position control systems [18], electro-mechanical and mechanical systems [19], unmanned free-swimming submersible systems [20,21], and damped vibroacoustic systems [22], are of high-order. The HODLS is always converted into the equivalent first-order form in earlier studies [23,24]. This transformation is probably the best choice for solving the problem of response analysis and estimation but not for controller design, because it may encounter the dimension explosion problem, destroy the physical meaning of original system parameters, increase excess computation load, lead to numerical unreliable phenomenon [25], and bring the extra smoothness requirement to control input [26,27].…”