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

Ozhikenov K. Nurgizat Y. Ayazbay A.-A. Uzbekbayev A. Sultan A. Nussibaliyeva A. Zhetenbayev N. Kalykpaeva R. Sergazin G.
December 2025 Multidisciplinary Digital Publishing Institute (MDPI)

Sensors
2025 #25 Issue 24

Affordable, sensor-driven lower-limb prostheses remain scarce in middle-income health systems. We report the design, numerical justification, and bench validation of a semi-active transfemoral prosthesis featuring surface electromyography (EMG) control and inertial sensing for low-resource deployment. The mechanical architecture combines a titanium–aluminum–carbon composite frame (total mass 0.87 kg; parts cost < USD 400) with topology optimization (SIMP) to minimize weight while preserving stiffness. Finite-element analyses (critical load 2.94 kN) confirmed structural safety (yield safety factor ≥ 1.6) and favorable fatigue margins. A dual-channel sensing scheme—surface EMG from the rectus femoris and an IMU—drives a five-state gait finite state machine implemented on a low-power STM32H platform. The end-to-end EMG→PWM latency remained <200 ms (mean 185 ms). Bench tests reproduced commanded flexion within ±2.2%, with average electrical power of ~4.6 W and battery autonomy of ~5.7 h using a 1650 mAh Li-Po pack. Results demonstrate a pragmatic trade-off between functionality and cost: semi-active damping with EMG-triggered control and open, modular hardware suitable for small-lab fabrication. Meeting target metrics (mass ≤ 1 kg, latency ≤ 200 ms, autonomy ≥ 6 h, cost ≤ USD 500), the prototype indicates a viable pathway to broaden access to intelligent prostheses and provides a platform for future upgrades (e.g., neural network control and higher-efficiency actuators).

EMG control , finite-element analysis , low-cost prosthetics , magnetorheological damping , rehabilitation engineering , semi-active knee , topology optimization , transfemoral prosthesis

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Department of Robotics and Technical Tools of Automation, Satbayev University, Almaty, 050013, Kazakhstan
Department of Electronic Engineering, Almaty University of Power Engineering and Telecommunications Named Gumarbek Daukeyev, Almaty, 050062, Kazakhstan
Department of Science and Innovations, ALT University Named After Mukhamedzhan Tynyshpaev, Almaty, 050013, Kazakhstan

Department of Robotics and Technical Tools of Automation
Department of Electronic Engineering
Department of Science and Innovations

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