Exponential time-varying sliding mode flight control design for a hypersonic cruise air vehicle

To deal with aerodynamic parametric uncertainties in cruise control of hypersonic air vehicle, an exponential time-varying sliding mode control (ETVSMC) algorithm with global robustness is proposed in this paper. A new exponential time-varying sliding surface is presented based on the exact linearization of the longitudinal model, and a corresponding high order sliding mode control algorithm is designed. The proposed control law guarantees the sliding mode occurrence from beginning to end and eliminates the reaching phase of time-invariant sliding mode control (SMC). In this way, the global robustness against parametric uncertainties is guaranteed. The stability is proved by the Lyapunov stability principle. The control parameters are optimized by using genetic algorithms (GA) with penalty function to minimize the index function, consisted of the integral of system errors and the penalty term of violation of parameter constraint. Simulations are employed to illustrate the effectiveness of the proposed method.