Design parameters and torque profile modification of a spring-assisted hand-opening exoskeleton module

Area of Science:

• Biomedical Engineering
• Rehabilitation Technology
• Biomechanics

Background:

• Growing demand for effective hand rehabilitation orthotics post-stroke.
• Current exoskeleton technologies struggle to accurately mimic hand biomechanics.
• Previous hand modules lacked optimal assistance profiles for patient recovery.

Purpose of the Study:

• To present data-driven design parameters for the ArmAssist-2.0 hand module.
• To enhance functionality and improve the assistance profile for post-stroke hand motor impairments.
• To address limitations in existing passive hand orthoses.

Main Methods:

• Incorporated adjustable linkages for broader user fit.
• Redesigned joint locations to better represent hand biomechanics.
• Developed an impairment-appropriate torque profile using interchangeable springs and variable moment arms.

Main Results:

• The revised ArmAssist-2.0 shows improved joint locations, adjustability, and metacarpophalangeal (MCP) joint force profile.
• The new assistance profile maintains a nearly linear relationship, better matching patient needs.
• Comfortable fit and improved functionality were noted for most joints.

Conclusions:

• The ArmAssist-2.0 demonstrates significant improvements for hand rehabilitation after stroke.
• The device offers a more accurate and adjustable assistance profile compared to previous models.
• Challenges with the proximal interphalangeal (PIP) joint extension were identified, with potential solutions discussed.