Abstract
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.
Highlights
An electro-optical tracking system (EOTS) is a complex, high-accuracy device that is integrated with optical, mechanical, and electronic devices, and it has attracted increasing attention in recent decades [1], [2]
The novel compound controller is developed that integrates the advantages of a nonlinear extended state observer (ESO), a fractional-order nonsingular terminal sliding mode (FONTSM) manifold, and a super-twisting algorithm
For AAE, the one yielded by the developed control strategy is 53.6%, 32.1%, and 4.88% of the ones by the ESO+super-twisting algorithm (STA), ESO based integral sliding mode (ESO+ISM), and NTSM methods, respectively
Summary
An electro-optical tracking system (EOTS) is a complex, high-accuracy device that is integrated with optical, mechanical, and electronic devices, and it has attracted increasing attention in recent decades [1], [2]. In [27], to handle nonlinearities, a continuous FO nonsingular terminal sliding mode controller with dynamic SM manifold was designed for a class of second-order systems. To handle complex lumped uncertainties, a continuous FONTSM controller with time delay estimation was designed for cable-driven manipulators [29]. To the best of our knowledge, due to the complex uncertainties and disturbances in EOTS, it is difficult to implement high-performance tracking control using any of the existing control methods such as SMC, ESO-based methods, model-based methods, and PID. A nonlinear ESO-based FO nonsingular terminal super-twisting SMC strategy is developed in this study. The novel compound 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.
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