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In this work, an integral-type terminal sliding mode (TSM) controller with an asymptotic disturbance observer is developed. The proposed controller can be applied to a class of uncertain integrator systems with unknown external disturbances. In addition, the chattering phenomenon and the singularity problem in traditional TSM control and the influence of unknown external disturbances on the system are taken into consideration. For unknown external disturbances in practical applications, a disturbance observer with asymptotic estimation performance is constructed. Thus, the control strategy is developed to ensure chattering-free and eliminate the singularity problem. By comparing with the traditional TSM control, we expect to synthesize a more efficient chattering-free sliding mode controller. The integral-type TSM transforms the discontinuous sign function into the continuous smooth function. Furthermore, the proposed control algorithm can accurately compensate for the external unknown disturbance and exhibits better robustness. Finally, the simulation results demonstrate the effectiveness of the controller and the stability of the whole closed-loop system is strictly proved. [ABSTRACT FROM AUTHOR]

By introducing a set of exact disturbance estimators, a continuously tracking controller for a class of mismatched uncertain systems with exogenous disturbances will be proposed. The most appealing superiority is that the proposed exact disturbance estimators can not only estimate the external disturbances but also achieve an asymptotic estimation performance. Furthermore, with the help of a set of first-order asymptotic filters and an auxiliary system, the developed control algorithm is able to compensate for these total disturbances feedforwardly. Consequently, the whole closed-loop stability with an asymptotic tracking performance is strictly analyzed, and meanwhile applications are conducted to indicate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

Motivated by the desire to extend the well‐known robust integral of the sign of the error (RISE) feedback control to handle both matched and mismatched disturbances simultaneously, two novel continuous integral robust control algorithms with asymptotic tracking performance will be constructed for a class of high‐order uncertain nonlinear systems. By skillfully introducing a set of filtered error variables and asymptotic filters as well as an auxiliary system, they will be integrated via an improved backstepping framework. Significantly, the virtual control law integrated at each procedure will pass through a novel asymptotic filter and then the filtered signal will be adopted in the subsequent backstepping iteration. Notably, one of the control algorithms is constructed via the integral of the sign of the filtered error variable introduced at each step, which makes it incalculable due to the unmeasurable states. In order to implement this controller, two measures for calculating the sign function in terms of the filtered error variable will be expounded. More importantly, the stability of the closed‐loop system under each controller will be strictly proved and meanwhile application examples will be performed to demonstrate the theoretical results. [ABSTRACT FROM AUTHOR]

In this article, committed to extending the robust integral of the sign of the error (RISE) feedback control to the working condition of output feedback, a novel output feedback controller with a continuously bounded control input which combines the adaptive control and integral robust feedback will be proposed for trajectory tracking of a family of nonlinear systems subject to modeling uncertainties. A novel adaptive state observer (ASO) with disturbance rejection performance is creatively constructed to derive real‐time estimation of the unmeasured state signals. Moreover, a projection‐type adaption law is integrated to handle parameter uncertainties and an integral robust term is employed to deal with external disturbances. It is shown that asymptotic estimation performance and meanwhile asymptotic tracking result can eventually be derived. Simulation validations are implemented to demonstrate the high tracking performance of the presented controller. Notably, the synthesized control algorithm can be readily extended to the Euler–Lagrange systems. Typically, it can be extended to practical electromechanical equipment such as three‐dimensional vector forming robots to improve the real‐time forming accuracy. [ABSTRACT FROM AUTHOR]

Committed to further enhancing the achievable tracking performance, a novel disturbance-compensation-based composite multilayer neural network adaptive control algorithm is developed for a class of multiple input multiple output nonlinear systems with modeling uncertainties. Specially, an extended state observer is utilized to estimate the exogenous disturbance and meanwhile predict the system state. Moreover, the nonlinear function uncertainties are approximated by the multilayer neural networks. Furthermore, the modeling uncertainties can be compensated in a feedforward manner. Notably, the multilayer neural network weights are updated via the composite adaption laws driven by the output tracking error and the prediction errors of the system state and control input, which brings improved function approximation performance. Finally, the application results demonstrate the efficacy of the integrated intelligent controller. [ABSTRACT FROM AUTHOR]

In this paper, a novel nonlinear robust controller ensuring time-varying output constraints for the double-rod hydraulic servo systems in the presence of largely unknown matched and mismatched disturbances is proposed. By employing two extended state observers for each channel of the load dynamics and pressure dynamics of the considered hydraulic system, the large matched and mismatched disturbances are successfully compensated. In addition, a time-varying barrier Lyapunov function (BLF) of asymmetric type has been employed to make sure that the position output is never violated. The resulting controller is synthesized using the backstepping procedure. The stability of the whole closed-loop hydraulic system associated with the dual extended state observer (ESO)-based controller is strictly guaranteed. In theory, the proposed control strategy can not only ensure the output satisfy the preset constrained space, but also enhance the output tracking performance when the system faces various largely unknown disturbances. The effectiveness of the proposed controller has also been demonstrated via comparative simulation results. [ABSTRACT FROM AUTHOR]

In this paper, adaptive compensation with a robust integral of the sign of the extended error (RISEE) feedback is developed for high precise tracking control of systems in the presence of simultaneous structured and unstructured uncertainties. To handle various uncertainties existing in the system in one controller, we propose an adaptive RISEE controller (ARISEE), in which an adaptive law based on the improved discontinuous projection method is synthesized to handle parametric uncertainties and the RISEE robust term to attenuate unmodelled disturbances. Moreover, the present controller does not need a priori knowledge on the bounds of the lumped disturbances and the gain of the designed robust control law can itself be tuned. The major feature of the proposed controller is that it can theoretically guarantee global asymptotic tracking performance with a continuous control input, in the presence of parametric uncertainties and unmodelled disturbances via Lyapunov analysis. Comparative numerical results verify the effectiveness of the proposed non-linear controller. [ABSTRACT FROM AUTHOR]