“…Apart from the applications mentioned above, SOS theory was also used to study other control problems, such as optimal control (Ichihara, 2009), mixed H 2 / H ∞ control (Ma et al, 2012) and non-linear robust control of a hypersonic aircraft (Ataei and Wang, 2012). Generally, the output feedback approaches based on SOS technique are non-convex (Chae et al, 2014; Nguang et al, 2011; Zheng and Wu, 2009, 2011) and thus the computational difficulties are unavoidable. As a result, most of the existing results adopt the state feedback to design controllers.…”