Multichannel Electrotactile Feedback With Spatial and Mixed Coding for Closed-Loop Control of Grasping Force in Hand...

Area of Science:

• Biomedical Engineering
• Neuroscience
• Rehabilitation Engineering

Background:

• Somatosensory feedback enhances myoelectric prosthesis utility and embodiment.
• Current feedback often uses single-channel stimulation for grasping force.
• A need exists for integrated, multichannel tactile feedback solutions.

Purpose of the Study:

• To present an integrated, compact, multichannel solution for somatosensory feedback in myoelectric prostheses.
• To evaluate two coding schemes (spatial and mixed modulation) for tactile feedback.
• To compare tactile feedback with visual feedback in prosthesis control tasks.

Main Methods:

• Developed an integrated system with an array electrode and programmable stimulator.
• Tested spatial and mixed (spatial and frequency) modulation coding schemes (15 levels).
• Evaluated performance in able-bodied subjects using psychometric tests and force control tasks (grasping, force tracking) with real and simulated prostheses.

Main Results:

• Mixed and spatial coding schemes showed similar performance in force control tasks, despite psychometric differences.
• Tactile feedback was as effective as visual feedback in routine grasping tasks.
• A conceptual model was proposed, highlighting feedback uncertainty, task nature, and feedforward control reliability as key performance factors.

Conclusions:

• Integrated multichannel tactile feedback systems are viable for myoelectric prostheses.
• Both spatial and mixed coding schemes are effective for force control.
• The proposed model provides a framework for designing closed-loop myoelectric prostheses with tactile feedback.