Exact Tracking Under Unknown Switching Control Directions and Input Delay: A Predefined-Time Control Approach for Multiagent Systems
Most existing results on nonlinear systems with unknown control directions (CDs) focus on asymptotic tracking. This article investigates the problem of adaptive predefined-time (PT) precise tracking for a class of nonlinear multiagent systems (MASs) with unknown finitely switching CDs and time-varying input delay. A novel control framework is established by introducing monotonically increasing sequences, which extends the classical Nussbaum function methodology to scenarios involving finitely switchable and completely unknown CDs via a proof by contradiction mechanism. Moreover, to compensate for the input delay, a class of delay compensation signals is introduced. By incorporating fuzzy logic systems and bounded estimation techniques, it is rigorously proven that the tracking error converges to zero within a PT, while simultaneously ensuring that full-state constraints are satisfied and all closed-loop signals are semiglobally ultimately bounded. The proposed method offers improved control performance and a broader applicability compared to existing approaches. Numerical simulations are provided to demonstrate the effectiveness of the proposed strategy.