Chapter 2. Prehension

Appendix D - Prosthetic and Robotic Hands 409
Table D.2 (continued) Commercially available mechanical hands
As body-powered devices with one degree of freedom, they can be
opened or closed voluntary. They consist of a thumb and four
fingers (although in some only two fingers are active). The thumb
is a virtual finger 1, and the fingers are virtual finger 2. The four
fingers can act as a VF3. (T=thumb; I=index, M=middle, R=ring,
L=little) (from Iberall, Beattie, & Bekey, in press; reprinted by
permission).
Manufacturer and Control Opp VF1 VF22 VF3
Name
New York University
Number 1 Hand voluntary pad T I-M&R-L
opening
I-M-R-L
United States
Manufacturing Co.
Adj. Mechanical voluntary pad T I-M-R-L
Hard Hands opening
I-M-R-L
Mechanical Soft voluntary pad T I-M&R-L
Hands opening
I-M-R-L
Hugh Steeper, Ltd.
Mechanicalhands vol. pad T I-M-R-L
open/closing
I-M-R-L
D.2.3 Commercially available mechanical hands
Hands have a thumb and four fingers, although not all four are
functional. They are covered with life-like cosmetic gloves that
improve their appearance but diminish their versatility. Having one
degree of freedom, these mechanical devices can be powered and
controlled as voluntary opening or closing. Artificial hands are rarely
used by bilateral amputees, because hooks are so much more
functional (Wilson, 1989). Another disadvantage of hands is the bulk
and weight (about 18 oz or more vs 3-4 oz for an aluminum hook,
Sears et al., 1989). Without feedback, other than visual and auditory
2While all four fingers are present in these hands, not all four fingers are active in
all of them. An ampersand is used for hands where the ring and little fingers are
not active.