Assist-As-Needed Backstepping Control of Lower-Limb Exoskeletons with Human Effort Estimation and Comparative Evaluation Against Sliding Mode and PID Controllers. - Hamza, Mukhtar Fatihu; Isa, Abdulbasid Ismail; Alqahtani, Abdulrahman; Rokbani, Nizar (Applied Sciences (2076-3417), 2026)