Development of Myoelectric Control Module for Prosthetic Hand with Artifact Removal during Sensory Electrical Stimulation

Evoked Tactile Sensation (ETS) with transcutaneous electrical nerve stimulation (TENS) can provide amputees with a non-invasive neural interface for sensory feedback. However, sensory stimulation at the projected finger map (PFM) on the stump skin causes interference in surface electromyographic (sEMG) signals used for prosthesis control. This study developed a practical solution that combined hardware blanking and software filtering to eliminate stimulus artifacts in real-time. A synchronized blanking circuit was inserted after the differential amplifiers to partially remove artifact spikes. EMG signal was then sampled and further processed by a digital signal processor (DSP). A digital comb filter removed the remaining artifacts at all harmonic frequencies of stimulation. The filtered EMG was rectified, and its envelope was extracted to control prosthetic hand. This technique was tested for its effectiveness in removing stimulus artifacts in three ablebodied subjects and in one transradial amputee operating a Bebionic hand. Results in able-bodied subjects indicated that the technique was effective in removing stimulus artifacts in EMG under different conditions. In the amputee subject, grasp control using the Bebionic hand was obtained with simultaneous sensory stimulation in the ipsilateral stump. The amputee subject achieved an average success rate of 90% for identifying the length of grasped objects. Tests confirmed that the technique is adequate to remove stimulus artifacts from EMG signals and allows control of the Bebionic hand with simultaneous sensory stimulation.