Switching Fixed-Time Control for Interconnected Nonlinear Systems With Unknown Control Directions and Unmodeled Dynamics

This article investigates the fixed-time control problem for a class of uncertain p-normal interconnected nonlinear systems with output constraints. Different from the existing fixed-time control results, unmodeled dynamics are allowed in the system model and the unknown control coefficients under consideration are time varying with nonidentical signs. To deal with this challenge, by applying the adding a power integrator method, a decentralized adaptive controller is built with a switching parameter to compensate unknown parameters. Based on fixed-time control framework, a logic-based switching rule is established to tune the switching parameter online, in which the Lyapunov-like boundary functions are utilized to replace the Lyapunov function containing inexact values brought by unmodeled dynamics. Then, with the aid of Lyapunov stability theorem, it is proved that the system output never violates the prespecified constraints and all state variables converge to zero within a fixed time. Finally, the validity of the presented method is demonstrated by a numerical simulation.