Design, Control, and Evaluation of a Multijoint Lower Limb Soft Exosuit

Soft exosuits offer distinct advantages for human motion assistance; however, multijoint actuation strategies frequently encounter challenges associated with actuator redundancy. Conventional designs, typically employing independent actuator and Bowden cable configurations per joint, impose substantial mass penalties that undermine the inherent lightweight potential of soft exosuit technology. This study introduces a novel soft exosuit system integrating a controllable anchor mechanism and a single-motor, dual-drive transmission system. This integrated approach effectively mitigates the actuator redundancy inherent in multijoint assistance paradigms. The implemented system facilitates the sequential delivery of assistance for ipsilateral hip flexion and ankle plantar flexion within a single gait cycle through precisely timed, gait-phase-based control strategies. The article details the exosuit architecture, encompassing the controllable anchor, an integrated dual-drive actuation unit, an automatic tensioning system, and a biomechanically informed wearable textile interface. Addressing the significant challenge of modeling the complex, nonlinear dynamics governing soft exosuit-human interaction, a model-free adaptive control (MFAC) strategy employing a single-input-single-output (SISO) controller architecture was developed and implemented for precise assistance magnitude regulation. Experimental validation demonstrated significant biomechanical efficacy: surface electromyography (sEMG) signal amplitudes exhibited reductions ranging from 7.7% to 17.7% across key lower limb musculature. Furthermore, a 14.7% reduction in net metabolic rate was observed during loaded walking. These findings substantiate that the proposed system enhances biomechanical assistance performance while concurrently reducing metabolic energy expenditure.