A pilot study of the SMG controlled prosthesis

The majority of the upper limb powered prosthetic devices are controlled by the surface electromyography (SEMG) now. But most commercial myoelectric prostheses can provide only one practical degree of freedom (DOF), directed by the flexion-extension of arm muscles. Though many alternative signal sources have been investigated for prostheses control, such as the mechanical force, myoacoustic signal, tissue morphological changes, and EEG, these alternative approaches are mostly the laboratory products. The sonography has been commonly used to detect the morphological information of human muscles in both static and dynamic conditions. We named the signal about the muscle morphological changes derived from ultrasound as sonomyography (SMG). In this study, we demonstrated the feasibility to use the muscle thickness deformation SMG as a new signal source to control one DOF prosthesis. The thickness deformations of the extensor carpi radialis muscle were measured during the wrist extension and flexion process to substitute the SEMG signal to control a reconstructed commercial myoelectric prosthesis. The results suggested that muscle deformation SMG could well control the prosthesis to open and close in the off-line way.