Cylindrical prehension

FIGURE 32.18 Schematic of the prehension patterns of the hand as defined by Keller, Taylor, and Zahn (1947) (al) palmar prehension (three-jaw chuck), (o2) palmar prehension (two finger), (b) tip prehension, (c) lateral prehension, (<0 hook prehension, (e) spherical prehension, (/) cylindrical prehension. In a handlike prosthesis, it takes two to four independently controlled degrees of freedom to implement these prehension patterns. In a non-hand-like device, a single-degiee-of-free-dom device such as a split hook can be used. 

A study done at Ae University of California at Los Angeles (UCLA) (Taylor, 1954) on human prehension force indicated that adult males could produce maximum mean forces of 95.6 N (21.5 Ibf) of palmar prehension, 103 N (23.2 Ibf) of lateral prehension, and 4(X) N (90 IbO of cylindrical grasp. In light of another (unpublished) UCLA study that showed that forces up to 68 N (15 Ibf) were needed for carrying out activities of daily living, Peizer et al. (1969) proposed that 68 N (15 IbO be a minimum standard for the maximum prehension force for electric prehensors (Heckathome, 1992). 

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