Variable Exponent Fixed-Time Optimized Sliding Mode for Quadrotor Attitude Control

This paper proposes a novel variable exponent fixed-time nonsingular terminal sliding mode control (FxTNTSMC) design for robust attitude tracking of a quadrotor in the presence of disturbances. Unlike conventional fixed-time control, the exponent in the proposed FxTNTSMC can adjust the positive constant, either greater or less than 1, depending on whether the system states are far from or close to the desired point, respectively. This variable exponent approach enhances both transient and steady-state performance while reducing control effort. The gain parameters of the proposed controller are also optimized using the Sine-Cosine algorithm technique. Further, the proposed scheme effectively mitigates the impact of disturbances while ensuring accurate trajectory tracking response. Lyapunov stability theory is employed to prove fixed-time convergence of all system states. Numerical simulations demonstrate the effectiveness and robustness of the proposed control method compared to the existing techniques.