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Fig. 3 | Journal of NeuroEngineering and Rehabilitation

Fig. 3

From: EMG Biofeedback for online predictive control of grasping force in a myoelectric prosthesis

Fig. 3

Visual scene shown to the subjects during the experiments including a snapshot of the screen (a) before contact and (b) after contact. The real prosthesis (Michelangelo hand) hidden from the subjects’ view grasped a stiff cylindrical object, and this was presented to the subject in the form of a virtual gripper grasping a virtual target object. Horizontal bars, red for the flexor and blue for the extensor, showed a continuous feedback about the current level of muscle activity (prosthesis control signals). As long as the myoelectric bars did not reach the respective black lines, the myoelectric activity was subthreshold (i.e., a dead zone area resulting in zero control input to the prosthesis). Semi-transparent blue bar indicated the hand grasping force and the green vertical line was the target force level. During the routine grasping, the target force was stationary, while in the force steering task, it was moving according to the time profile of a reference force trajectory

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