Improved Full-Error Constrained Control for Unknown Interconnected Time-Delay Nonlinear Systems With Input Saturation

In this article, the problem of improved full-error constrained control for unknown interconnected nonlinear time-delay systems with input saturation is investigated. To address this issue, auxiliary systems and a filter are constructed to generate modified signals, which are added to the constraint boundaries to prevent full dynamic errors (tracking error and virtual errors) from violating flexible boundaries and causing singularity problems during input saturation or drastic changes in the reference signal. To enhance the dynamic performance of all system errors, the error-driven nonlinear feedback technique is applied to all transform errors, enabling them to possess self-tuning characteristics. Furthermore, a decentralized adaptive learning constrained control strategy is proposed by employing fuzzy logic systems with an incremental adaptive mechanism to approximate complex uncertainties. The stability analysis demonstrates that the proposed control scheme guarantees the semi-global uniform ultimate boundedness of all signals in the closed-loop system, and the full dynamic errors are constrained within self-adjustable performance boundaries in the presence of input saturation. Finally, simulation results demonstrate the efficacy of the presented control strategy.