Trajectory Tracking Control for Electro-Optical Tracking System Using ESO Based Fractional- Order Sliding Mode Control

In this study, to achieve high trajectory tracking performance in electro-optical tracking systems under strong nonlinear disturbances and uncertainties, we develop a nonlinear extended state observer (ESO) based fractional-order sliding mode control. When compared with previous work, the new compound control strategy is attractive in terms of the following three points. First, a novel controller is developed that integrates the advantages of a nonlinear ESO, a fractional-order nonsingular terminal sliding mode (FONTSM) manifold, and a super-twisting algorithm. Second, the nonlinear ESO is employed to estimate the disturbances and uncertainties without explicit knowledge of the system model. Third, a FONTSM manifold-based super-twisting algorithm is integrated into the controller to enhance the system robustness. The FONTSM manifold has a faster dynamical response, more flexible sliding manifold structure, and better control results than its integer-order NTSM counterpart. The finite-time convergences of the ESO and controller are both proved by the Lyapunov method. Finally, the comparative experimental results demonstrate the effectiveness and superiority of the developed control strategy with respect to existing approaches.