An Approximation-Free Methodology to Tracking Control of Pure-Feedback Nonlinear Systems With Application to Hypersonic Flight Vehicles

This article addresses the problem of approximation-free prescribed performance control (PPC) for a class of non-triangular pure-feedback nonlinear dynamics whose nonaffine function of each subsystem is relaxed to rely on the whole state vector. The assumption made in this work is far more relaxed than all the available works in the sense that some commonly used Lipschitz condition or setting bounding function are never involved and only the continuity of nonlinearities are required. Furthermore, the proposed low-complexity PPC is simplified because neither approximators (neural networks and fuzzy logic systems) nor adaptation technique are embeded in the control design. By utilizing the barrier functions, some transient and steady state performances can be also preserved, while guaranteeing the closed-loop stability. Simulation results of hypersonic flight vehicles (HFVs) dynamics eventually validate the effectiveness of the proposed methodology.