Electrotactile EMG feedback improves the control of prosthesis grasping force

Area of Science:

• Biomedical Engineering
• Neuroprosthetics
• Rehabilitation Robotics

Background:

• Active prostheses lack direct mechanical feedback, hindering user embodiment and acceptance.
• Somatosensory feedback can compensate for this detachment, improving prosthetic functionality.
• Electrotactile stimulation offers a viable method for delivering sensory feedback.

Purpose of the Study:

• To compare a novel electromyography feedback (EMG feedback) approach with classic force feedback (force feedback) for prosthetic control.
• To evaluate the effectiveness of EMG feedback in a realistic grasping task using an electrotactile interface.
• To assess the impact of feedback type on precision, performance, and error reduction.

Main Methods:

• Eleven intact-bodied subjects and one transradial amputee performed a grasping task.
• Feedback was delivered via an electrotactile interface using mixed spatial/frequency coding for 8 discrete levels.
• EMG feedback transmitted myoelectric signal amplitude; force feedback transmitted grasping force.

Main Results:

• EMG feedback significantly improved myoelectric command precision (23-36%) and force control precision (12-32%) compared to force feedback.
• EMG feedback reduced the magnitude and dispersion of absolute error, indicating enhanced overall performance.
• Similar improvements were observed in the transradial amputee subject.

Conclusions:

• Online EMG feedback enables predictive control by leveraging the anticipatory relationship between EMG signals and force output.
• EMG feedback proved superior to force feedback under realistic conditions, including limited feedback resolution and time constraints.
• This approach enhances prosthetic control, potentially increasing user embodiment and acceptance.