Variable admittance control with sEMG-based support for wearable wrist exoskeleton.

Area of Science:

• Robotics
• Neurorehabilitation
• Biomechanics

Background:

• Wrist function impairment significantly impacts daily living post-stroke.
• Wearable exoskeletons offer potential for increased therapy dosage and gravity mitigation.
• Controlling non-backdrivable exoskeletons poses stability challenges, especially with biological joint stiffening.

Purpose of the Study:

• To implement and evaluate a variable admittance control scheme for a wearable wrist exoskeleton.
• To assess the stability and effectiveness of the control scheme in human-robot interaction.
• To investigate the combined effects of variable admittance, sEMG, and gravity-based control for stroke survivors.

Main Methods:

• A variable admittance control scheme was implemented on a 1-DOF wrist exoskeleton.
• The damping parameter was dynamically adjusted to manage wrist stiffness and interaction stability.
• sEMG- and gravity-based controllers were integrated and tested on healthy participants and stroke survivors.

Main Results:

• Variable admittance control enhanced interaction stability but reduced system transparency.
• Coupling variable admittance control with sEMG-based control improved wrist functionality in stroke survivors, especially at extreme ranges.
• The combined control approach benefited patients with higher impairment levels.

Conclusions:

• Variable admittance control is effective for stabilizing wrist exoskeleton interaction.
• Integrated sEMG and gravity-based control, with variable admittance, shows promise for stroke rehabilitation.
• Future research should focus on customizing control parameters for diverse impairment levels.