Myoelectric limbs

Movement of powered prosthetic devices such as arms, hands, and legs can be controlled with the surface myoelectric signal (MES) in a very natural way. The person with the prosthesis only has to attempt to make the intended movement and this produces minute contractions of residual muscles similar to contractions in an intact limb. 

In addition to the mechanical performance Umitations of prosthetic limbs, the other major impediment to full restoration of limb capability with an artificial device is the command and control interface between the prosthesis and amputee user. The typical approach for direct amputee control of a prosthetic limb is to use myoelectric potentials from muscles in the amputee s residual limb as user commands to the limb... 

FIGURE 42.3 (a) The i-limb ultra myoelectric hand and (b) i-limb skin natural cosmetic covering. (Touch Bionics... 

Practical inputs typically come from muscular activity, (1) directly, (2) indirectly through joints, and (3) indirectly from by-products of muscular contraction (myoelectricity, myoacoustics, muscle bulge, and mechanical/electrical impedance). Although signals can be obtained from brain waves, voice, feet, eyes, and other places, these sources of control have not been shown to be practical for artificial limb control (Childress 1992). 

The Russian hand was the first semipractical myoelectric hand to be used clinically. This hand also had the distinction of being the first to use transistors (germanium) to process the myoelectric control signal (Childress, 1985). In this country, following World War II, the Committee on Artificial Limbs contracted with IBM to develop several electrically powered limbs. These were impressive engineering feats in their day but never found use outside the laboratory (Klopsteg and Wilson, 1956). 

FIGURE 32.29 A standard transradial myoelectric prosthetic interface (socket). The battery pack, wrist unit, and myoelectrodes are all fitted into a custom-made laminated prosthetic socket and forearm. The sock is hibri-caled after a mold made ftmn the amputee s residual limb. 

Parker, P., Englehart, K., Hudgins, B. (2006). Myoelectric signal processing for control of powered limb prostheses. Jnl. of Electromyography and Kinesiology, 16, 541-548. 

Yonghong, H., glehart, K., Hudgins, B., Chan, A. (2005). A Gaussian mixture model based classification scheme for myoelectric control of powered upper limb prostheses. IEEE Tran, on Biomedical Engineering, 52 (11), 1801-1811. 

Touch Bionics is a leading developer of advanced upper-limb prosthetics (ULP). One of the two products now commercially available from this company, are the i-LIMB Hand , is a first to market prosthetic device with five individually powered digits[4]. This artificial limb looks and acts like a real human hand and represents a generational advance in bionics and patient care. The i-LIMB Hand is controlled by a unique, highly intuitive control system that uses a traditional two-input Myoelectric (muscle signal) to open and close the hand s [5],... 

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