Finite-time Prescribed Performance Control with RBFNN for the HFV Longitudinal Model

A method for designing the finite-time prescribed performance controller with RBFNN (Radial Basis Function Networks) is proposed for the HFV (Hypersonic Flight Vehicle) longitudinal attitude systems with parameters uncertainties and time-varying disturbance. Firstly, the appointed-time prescribed performance functions for outer-loop and inner-loop are designed respectively, which aims to restrain the transient and steady-state performance of command tracking errors. Compared with the traditional prescribed performance function, the proposed method can guarantee that the errors convergence to the set stability precision at the appointed time. Furthermore, the error-transform function is applied to transform the guidance command errors into un-limited boundary, which can ensure the error satisfy the constraint condition by means of controlling the transformed errors. Then, the virtual control law of outer-loop subsystem and the actual control law of inner-loop subsystem are designed independently, and the lumped disturbances are estimated by the RBFNN, a novel finite-time tracking differentiator is applied to avoid the 'explosion of terms' problem in the control law design process. Ultimately, comparative simulations with parametric uncertainties and time-varying disturbance are performed to demonstrate that the proposed method in this paper can effectively satisfy the prescribed performance constraints.