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Corresponding Author

Osamah A. Aldoori

Document Type

Article

Keywords

Sliding Mode Control (SMC), Barrier Function (BF), Adaptive SMC, Rigid spacecraft model

Abstract

Sliding mode control (SMC) has demonstrated significant success in controlling nonlinear systems, particularly those subject to disturbances and uncertainties. However, due to the negative effect of the Chattering phenomenon, it has become necessary to employ an Adaptive Sliding Mode Controller (ASMC) capable of handling time-varying disturbances. This work presents a two-phase Barrier Function (BF) based Adaptive Sliding Mode Controller (BFASMC). This controller is designed to achieve robust stability and performance of nonlinear systems without prior knowledge of disturbance bounds, and applied to satellite Attitude control. The first phase is a constant gain adaptation to ensure rapid convergence, while, the second phase is a BF adaptation mechanism to maintain the system states in predefined neighborhood of zero. Stability and finite-time convergence are rigorously established using Lyapunov criteria. A comparison with Conventional Sliding Mode Control (CSMC) and the Plesten et. al. adaptation strategy (we will refer to it later as PASMC), which is considered close to the method in this research has been made to demonstrate the strength of the proposed method against them. Simulation results demonstrate enhanced adaptability, robustness, and smoother control behavior. The effectiveness of the proposed approach is validated by simulation results for satellite attitude control under external severe time varying disturbances. The simulation results were very promising, as the results, show the proposed controller tracks the states to desired trajectories accurately with steady sate error up to (0.0029 rad/s) and minimize control effort down to (0.4251 Nm) with excellent adaptation, disturbance reduction and chattering elimination.

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