A Comparative Case Study of EMG-Driven Controllers in Transtibial Prostheses.

Area of Science:

• Biomedical Engineering
• Rehabilitation Robotics
• Prosthetics and Orthotics

Background:

• Lower limb amputation significantly impacts mobility and quality of life.
• Current powered transtibial prostheses face challenges in user control and adaptability.
• Electromyography (EMG)-driven control offers potential for advanced prosthetic functionality.

Purpose of the Study:

• To comparatively analyze a novel EMG-driven variable impedance controller (VIC) against a hybrid controller (HC).
• To evaluate controller performance in a transtibial amputee during various ambulation tasks.
• To assess user control, adaptability, and biomechanical output differences.

Main Methods:

• Developed a VIC and an HC integrating a musculoskeletal model with a finite-state machine impedance controller.
• Modeled gastrocnemius and tibialis anterior muscles using a Hill-type model.
• Conducted biomechanical testing with a transtibial amputee using residual limb EMG signals for level ground, stairs, and ramps.

Main Results:

• VIC demonstrated more repeatable performance, enhanced perceived control, and greater power output.
• Significant effect sizes for peak power were observed with VIC during ramp ascent and high-speed walking.
• HC facilitated superior transitions between gait subphases, particularly stair ascent, showing higher ROM and peak power.

Conclusions:

• VIC offers improved predictability and user comfort, enhancing perceived control.
• HC provides better adaptability for complex transitions like stair negotiation.
• Findings guide future research in optimizing EMG-based control strategies for prosthetic limbs.