A Novel Hybrid Robust Control Design Method for F-16 Aircraft Longitudinal Dynamics

This paper presents a hybrid robust control design method for a third-order lower-triangular model of nonlinear dynamic systems in the presence of disturbance. In this paper, a novel control design is presented systematically to synthesize a robust nonlinear feedback controller, called backstepping sliding mode control (BSMC), for the proposed system by a combined approach of backstepping design and sliding mode control. In this approach, a family of the “sliding surface” is introduced in state transformations. Then, a smooth switching function of the sliding surface is introduced and enforced to include in virtual feedbacks and a real control law from the control selection phrases of the backstepping design loop. The achieved control method proves a well-tracking command with asymptotic stability, provides a robustness in the presence of uncertainties, and eliminates completely a chattering phenomenon. The application of flight-path angle control corresponding to the longitudinal dynamics of a high-performance F-16 aircraft simulation model is implemented. Under some assumptions, full nonlinear longitudinal dynamics is reformed into a lower-triangular system for a direct application to formulate a control law. A closed-loop system is achieved for in-flight simulation with different flight profiles for a comparison of the existing methods. Also, an external disturbance on different loading/unloading conditions in flight is applied to verify and validate robustness of the proposed control method.

Robust Synchronization of Duffing System Using Integral Action in Backstepping Design

Backstepping is a realistic nonlinear control design algorithm based on Lyapunov design approach; therefore, it automatically ensures the convergence of the regulated variable to zero. In this paper, it has been proposed for robust synchronization of Duffing chaotic systems. Integral action is being used to enhance the control action of the controller in steady state against the disturbances. The salient feature of the design is that the derived control doesn’t contain any derivative terms; consequently it simplifies the controller realization. The effectiveness of the proposed controller has been demonstrated in simulation studies. The performance of the controller has been evaluated not only based on its synchronizing ability but also the disturbance rejection ability of the controller has been verified.