PNIPU scientists previously developed their own linear motor for prostheses, and now they have found a way to improve its design to simplify production and improve the characteristics of finished products.
Experts suggested replacing classic rotary motors with spherical and linear ones to avoid heaviness and noise. The next step was to optimize the design to increase traction force — one of the main characteristics of prostheses.
Classic electric motors consist of a stator and a rotor. Scientists have improved the design of the stator slots, which made it possible to eliminate problems during winding laying. The new slot consists of two parts that clamp the winding, which simplifies the modular assembly of the motor.
After the design change, the average traction force of the motor was 10.3 N, and the oscillation range was 21.05 N. However, high oscillation makes it difficult to control the prosthesis, creating a lag in the system.
Modeling showed that the magnetic core steel is underutilized, since the induction is approximately 1.15 Tl with steel saturation at 1.8 Tl. Thus, scientists need to either reduce the amount of steel to lighten the prosthesis, or increase the supply voltage to increase power. In the first variant, reducing the thickness of the slot for the winding increased the number of turns from 63 to 75, which reduced the traction force oscillations by almost 50%, with a slight decrease in the force itself to 10.03 N, which is considered an acceptable loss. In the second variant, increasing the voltage from 3.7 V to 7.4 V increased the traction force to 22.2 N. The increase in oscillations can be compensated by the control system, which makes the second option more preferable.
PNIPU scientists proposed a new stator slot design for a linear motor in bionic prostheses and found that increasing the supply voltage expands the range of developed force. Applying the research results in practice will make prostheses more accurate, easier to use, and simplify their production.
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