Design and Testing of an Emg-Controlled Semi-Active Knee Prosthesis.

Area of Science:

• Biomedical Engineering
• Rehabilitation Engineering
• Prosthetics and Orthotics

Background:

• Affordable, sensor-driven lower-limb prostheses are limited in middle-income healthcare systems.
• There is a need for cost-effective and functional prosthetic solutions for transfemoral amputees.

Purpose of the Study:

• To design, justify, and validate a semi-active transfemoral prosthesis for low-resource settings.
• To achieve a balance between functionality, low cost, and ease of fabrication.

Main Methods:

• Developed a lightweight prosthesis (0.87 kg) using a titanium-aluminum-carbon composite frame (< USD 400 parts cost) with topology optimization.
• Implemented a dual-channel sensing system combining surface electromyography (EMG) and an inertial measurement unit (IMU) to control a five-state gait finite state machine.
• Validated structural integrity using finite-element analysis and performed bench tests to assess performance metrics like latency, power consumption, and battery autonomy.

Main Results:

• The prosthesis met target metrics: mass ≤ 1 kg, latency < 200 ms (mean 185 ms), autonomy ~5.7 h, and cost < USD 500.
• Bench tests confirmed accurate flexion control (±2.2%) with low average electrical power consumption (~4.6 W).
• Structural analysis indicated sufficient safety factors (≥ 1.6) and favorable fatigue margins under critical loads (2.94 kN).

Conclusions:

• The developed semi-active transfemoral prosthesis offers a pragmatic balance of functionality and cost, suitable for low-resource environments.
• The open, modular hardware design facilitates small-lab fabrication and provides a platform for future enhancements, such as advanced control algorithms.
• This prototype represents a significant step towards broadening access to intelligent prosthetic devices globally.