  Existing robotic lower-limb prostheses use autonomous control to address
cyclic, locomotive tasks, but they are inadequate to operate the prosthesis for
daily activities that are non-cyclic and unpredictable. To address this
challenge, this study aims to design a novel electromyography (EMG)-driven
musculoskeletal model for volitional control of a robotic ankle-foot
prosthesis. This controller places the user in continuous control of the
device, allowing them to freely manipulate the prosthesis behavior at will. The
Hill-type muscle model was used to model a dorsiflexor and a plantarflexor,
which functioned around a virtual ankle joint. The model parameters were
determined by fitting the model prediction to the experimental data collected
from an able-bodied subject. EMG signals recorded from ankle agonist and
antagonist muscle pair were used to activate the virtual muscle models. This
model was validated via offline simulations and real-time prosthesis control.
Additionally, the feasibility of the proposed prosthesis control on assisting
the user's functional tasks was demonstrated. The present control may further
improve the function of robotic prosthesis for supporting versatile activities
in individuals with lower-limb amputations.
