Multi-Input Higher-order Sliding Mode Control of Aeroelastic Systems With Uncertainties and Gust Load

Abstract

This paper presents the design of a higher-order sliding mode controller for finite-time stabilization of a multi-input multi-output nonlinear aeroelastic system with uncertain dynamics using leading-and trailing-edge control surfaces. The model describes the plunge and pitch dynamics of a prototypical wing section. It is assumed that the system parameters are not known precisely and external disturbance inputs are present in the model. The uncontrolled model exhibits limit cycle oscillations. The objective is to control the state vector of the system to the origin. A robust control law is designed for the finite-time trajectory control of the plunge and pitch angle trajectory. The control law includes a nominal finite-time stabilizing control signal designed for the system without uncertainties, and a discontinuous control signal for nullifying the effect of uncertain functions in the model. For the nominal control law design, the notion of geometric homogeneity is utilized and the discontinuous part of the controller is derived based on a second-order sliding mode control scheme. In the closed-loop system including the nominal and discontinuous control signals, finite-time control of the complete state vector associated with the plunge-pitch motion of the system to the origin is accomplished. Simulation results are presented which show the suppression of the limit cycle oscillations, despite parameter uncertainties and triangular, exponential, sinusoidal and random gust loads.