Summary
In this article, the adaptive and disturbance‐observer‐based (DO‐based) finite‐time tracking controllers are simultaneously considered for a surface vessel with output constraints. Two types of barrier Lyapunov functions (BLFs) are employed to deal with output constraints. The adaptive tracking controller is developed by elaborately applying tan‐type BLF and adaptive control technology, and the finite‐time trajectory tracking controller is rigorously proposed by the comprehensive application of log‐type BLF and finite‐time DO. Under these two controllers, the specified output constraints can be realized and the closed‐loop error systems are semi‐globally asymptotically stable. Simulation results are presented in detail to demonstrate the effectiveness of the two designed control strategies.
In this study, a nonlinear tracking controller is designed for a flexible-joint (FJ) robotic manipulator system subject to full-state constraints and external disturbances. First, a nonlinear disturbance observer (NDO) is introduced to guarantee that the respective disturbance can be estimated asymptotically. Then, state-dependent function (SDF) transformations are used to convert the original state-constrained system into a new unconstrained system. Subsequently, a NDO-based tracking controller is proposed to enable the output tracking error to converge to a predefined compact set that can be adjusted to be arbitrarily small. The boundedness of all the closed-loop system signals is rigorously proved. Finally, simulation results are presented that show the effectiveness of the proposed control algorithm.
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