Myoelectric Prosthetic Arm










Low Cost Myoelectric Prosthetic Arm

The project studies a low-cost 3-D printed trans-radial prosthetic arm. This involves the development of body-powered prostheses and then takes a step forward to an externally-powered prosthesis - a myoelectric prosthetic arm, which uses an EMG sensor to read electrical signals generated from the residual limb to achieve visual grasp motion by actuating the motors.

Electric arm- all fingers closed

Electric arm- 3 fingers pinch motion

  • The design was optimized to reduce the infill material and overall weight while maintaining structural integrity.

  • The final prototype is made of ABS plastic which is lightweight and has good impact strength.

  • Overall manufacturing and assembling cost for the product is ₹4500, which is 70% cheaper than the existing arm prosthesis in the market.

  • Our prototype weighs 1.23kg and can be easily maneuvered by the user.

  • This simple design provides two motions - grasp-hold motion and 3-fingers pinch motion - to the users.

Software Used:

  1. SolidWorks (3D CAD modeling)

  2. ANSYS Workbench (Structural Stress analysis)

  3. CURA- Ultimaker (3D printing)

Exploded View of the CAD Model

Programming and Calibrating the signal . . . .

  • The disposable surface electrodes are secured over the relevant muscles on the body surface, after initial skin preparation. These electrodes pick up the voltages produced by the contracting muscles.

  • The threshold value for control of the prosthetic hand was set at 300 by taking the average of maximum and minimum values. The prosthetic hand is activated when the sEMG signal exceeds the threshold value that is fixed while the muscles are contracted.

  • Actuation of the arm is done by comparing varying EMG signals with a set EMG threshold value.

  • Two force sensing resistors (FSR) are placed on the tip of fingers, one each for the index finger and thumb. A threshold FSR value is set.

      • When the value of these two FSR becomes greater than the threshold value, i.e. the arm is holding an object with a firm grip, the motors are programmed to stop its rotation. Thus, it is achievable to detect grasps. Hence the hand is capable to achieve a stable grasp.

  • A delay of 10 seconds is set to check if the EMG value is more than the EMG threshold value.




The Setup

Signal Testing