Aquila optimizer β-variable model-free adaptive fractional-order sliding-mode control for wheel slippage prevention in omnidirectional mobile robots.

Three-wheeled omnidirectional mobile robots (TWOMRs) are vital in firefighting owing to their maneuverability, but they struggle with wheel slip and instability on low-traction surfaces because of nonlinear traction dynamics. Therefore, this paper proposes an Aquila Optimizer β-variable model-free adaptive barrier-function fractional-order nonlinear sliding-mode control (AO-β(t)-MF-ABFFONSMC) strategy to achieve precise motion and mitigate slip. The framework integrates a sliding-mode disturbance observer, a model-free framework, an intelligent proportional-differential controller, and adaptive barrier-function fractional-order nonlinear sliding-mode control, while the Aquila Optimizer is used to optimize control parameters; this combination actively compensates for disturbances and estimation errors while minimizing chattering in TWOMRs. Simulation results show that the proposed controller outperforms others, providing robust, precise tracking and improved handling of slip and vibration in TWOMR across varying traction conditions.