مهدي گلي

Given the advantages of utilizing multiple satellites in space missions, controlling formation flying an‎d detecting actuator faults are of paramount importance. This dissertation focuses on the design of a nonlinear observer for actuator fault estimation in satellite formation flying using a predictor-corrector model. Depending on the problem assumptions, the dynamic an‎d kinematic equations governing the relative motion of satellites range from linear to nonlinear models subject to time-varying disturbances. In this research, nonlinear equations accompanied by disturbances are investigated. Model-based methods are employed for fault estimation, an‎d considering the nonlinearity of the system an‎d the presence of disturbances, an improved intermediate estimator has been designed. The advantages of this estimator include the absence of a matching condition requirement, the lack of necessity for fault boundedness, an‎d the elimination of the need for a predefined fault derivative bound. To enhance estimation accuracy an‎d convergence speed, two structures, PI an‎d PID, are proposed for the improved intermediate estimator; by tuning the design parameters (proportional, integral, an‎d derivative gains), the systemʹs performance in both transient an‎d steady-state regimes is improved. Stability analysis using Lyapunov theory an‎d the LMI (Linear Matrix Inequality) method demonstrates that the estimation error is uniformly ultimately bounded (UUB). Simulations further confirm the superiority of the proposed method over the nominal intermediate estimator. Since the relative motion equations are a subset of Lipschitz nonlinear systems, the proposed method can serve as an analytical solution for fault estimation in a broader class of nonlinear systems. In this regard, it is essential to consider the specific conditions governing satellite formation flying an‎d the constraints of nonlinear observers."

معادلات حركت نسبي , آرايش پروازي چند ماهواره , تخمين عيب , تخمين‌گر مياني , سيستم‌هاي غيرخطي ليپشيتز

Relative motion equations , Fault estimation , Intermediate estimator , Lipschitz nonlinear systems , formation flying

Mahdi Goli

Hosein Bolandi - Saeed Ebadollahi