Engineering Mechanics

Proceedings Vol. 12 (2006)

ENGINEERING MECHANICS 2006

Copyright © 2006 Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, Prague

 

J. Čulík
pages 46 - +12p., full text

The mechanical model of power grip of a human hand is described in the paper. The model consists from stiff bones of finger links and tendons and it enables calculation of stress state at bones and forces at tendons. They are solved two types of power grip: the power grip of some object, for example the tongs and power grip of bar of hanging man. Bones are supposed as ideal stiff and tendons as ideal flexible. Each finger link has its own tendon, the flexor for closing the hand and extensor for its opening. The tendons are situated at tendon vaginas without friction. The finger links are connected at joints without bending moments and they are supported by tendons. The tendon forces are calculated as a system of cables and pulleys near the joints. The 1st variant presumes that hand grips the object between the wrist and nth finger links, where n is input parameter. The number of working links n depends on object diameter. The tendon forces and stress values for a small object is less if the object is griped by the 3th links than for the 4th ones, a craftsman puts the tongs deeply to palm if he would grip the object with a greater force. The 2nd variant presumes that the all finger links grips the bar. The all fingers grip the object without the trump which only safes the hand position without stress. The described calculation algorithm was implemented on computer. The algorithm can be used for healthy hand and for pathologic form or for any missing finger links.

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