High-Performance Motion Control for Omnidirectional Assistive Wheelchairs Using Robust Fractional-Order Non-Singular Fast Terminal Sliding Mode Control to Enhance Riding Comfort

Robotics advancements have transformed assistive devices, enhancing independence for over a billion people with disabilities through innovations like three-wheeled omnidirectional mobile chair robots (TWOMCR). However, their complex mobility and environmental disturbances, like uneven terrain, hinder smooth control, risking abrupt stops. This study proposes a robust fractional-order non-singular fast terminal sliding mode controller (RFO-NFTSMC) to improve trajectory tracking and stability. The proposed controller ensures precise control while avoiding sudden stops due to uneven terrain or obstacles by addressing common issues like jitter and singularities. It balances rapid convergence with stability in unpredictable environments, outperforming to mainstream alternative such as fractional-order terminal sliding mode control (FO-TSMC), fractional-order fast terminal sliding mode control (FO-FTSMC), model predictive, and adaptive control in simulations. The controller's enhanced precision and resilience significantly boost user riding comfort and safety, demonstrating its potential for future intelligent mobility systems. The proposed controller marks a critical step toward reliable assistive robotics by tackling mobility challenges through robust adaptability.