In this study, with the help of a disturbance observer, an adaptive fractional-order sliding mode control scheme is designed to achieve trajectory tracking control of indeterminate manipulators. Firstly, the fractional-order non-singular fast terminal sliding mode (FO-NFTSM) surface is presented to increase the convergence velocity of the controller. Secondly, the adaptive reaching law is designed on the strength of the super-twisting algorithm to ensure the control performance of the approaching stage. Meanwhile, aiming at the compound disturbance existing in the manipulator system, an adaptive fixed-time sliding mode disturbance observer (AFSMDO) is introduced to settle the problem, which can estimate the lumped disturbance in real-time. Moreover, compensate for the system and raise the precision of the controller. The Lyapunov method is applied to certify the stability of the control system. Simulation experiments verify the superior property of the controller designed in this article.
In this paper, an adaptive fixed-time controller is raised for the manipulator system with uncertain disturbances to boost the rate and precision of its trajectory tracking and solve the convergence time dependence on the system's initial conditions. First, a nonsingular fixed-time sliding mode (SM) surface and a reaching law based on an arctangent function are constructed to enhance the control scheme performance. Second, the upper bound is difficult to obtain because of the uncertainty of the disturbance. The disturbance upper bound is estimated by adaptive techniques, which do not require a priori knowledge about the upper bound and effectively inhibit the effect of disturbance on the system. Finally, the fixed-time convergence of the states is analyzed by rigorous theoretical proof, and the validity of the presented control scheme is demonstrated by simulation.
For the high control performance of the manipulator system, a fixed-time control algorithm based on a super-twisting disturbance observer (STDO) is designed in this paper. Firstly, an STDO is proposed to process the disturbance and then compensate the system with feedforward for the issue that the lumped disturbance is difficult to determine. On this basis, the fixed-time sliding mode (SM) surface and adaptive reaching law are designed. The reaching law gains are changed by the adaptive law to enhance the robustness and anti-interference of the system. Meanwhile, the Lyapunov theory is used to examine the stability of the closed-loop system, and it is shown that the system state can converge to a specific area during the sliding and reaching phases. Finally, the superiority and effectiveness of the control strategy raised in this work are verified by simulation.
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