H_∞ sampled-data fuzzy control for attitude tracking of mars entry vehicles with control constraints

In this paper, the problem of designing an H_∞ sampled-data fuzzy controller is investigated for attitude tracking of Mars entry vehicles with control constraints. Initially, to overcome the difficulty of Takagi–Sugeno (T–S) fuzzy modeling, the original nonlinear error system is divided into a fast subsystem and a slow subsystem on the basis of two time-scale decomposition technique, where the fast subsystem describes the attitude dynamics and the slow subsystem describes the attitude kinematics. Dynamic inversion control method is subsequently employed to obtain the angular velocity command for the slow subsystem. Then, based on the angular velocity command and the T–S fuzzy model of the fast subsystem, a tracking error fuzzy system is derived for the sampled-data fuzzy control design. The existence condition of the constrained H_∞ sampled-data fuzzy controllers is provided in terms of linear matrix inequalities (LMIs). The proposed controller can exponentially stabilize the original nonlinear error system with an H_∞ tracking performance, provided that the timescale separation between the fast and slow subsystems is valid. Finally, simulation results illustrate the effectiveness of the proposed method.