Observer‐based control for nonlinear Hadamard fractional‐order systems via SOS approach

Abstract Practical stability refers to the notion that the origin is not an equilibrium point (EP) and that the system states tend to converge toward a sphere centered at the origin. The first goal of this paper is to analyze the concept of “practical stability” in Caputo–Hadamard fractional‐order derivative (CHFOD) systems. Then, using the Lyapunov approach, a polynomial fuzzy (PF) observer‐based controller for stabilizing CHFOD PF systems is created. The observer‐based control is innovative since it was created and proven using the sum‐of‐squares (SOS) method. In conclusion, a numerical illustration is provided to corroborate the theoretical findings.