Degrees of freedom

Disadvantages of existing prostheses

a) Absence of adaptability to the shape of objects, and as a consequence
the need for replacement terminals for different types of operations. Due to the rigid connection to the drive mechanism we have the following
negative effect: as soon as the first finger is in contact with the object,
the motion is blocked for the other fingers.
b). The second issue, which follows from the first: the ability of holding the prosthesis is not proportional
to the force on the cable. We can not be sure that the subject is firmly captured.
с).Prostheses Raptor type more suitable for the rapid capture of small items (such as a tennis ball).
They can not provide a large holding force (IMHO).

How can we solve these problems? The most perfect solution: the use of a hydraulic
system containing flexible fingers bendable fluid pressure, pamp, valves,feedback sensors, controller.
Such system would be expensive. But we can make an approximate mechanical analog of the hydraulic system.

The key idea provide an additional degree of freedom, to ensure adaptability.
First adaptive element - the finger.
Finger is able to capture objects of different shapes, due to the design, similar to a bicycle chain.
Each finger element can be bent 20 degrees toward the palm side. Flexion provided nonelastic cable,
return to the neutral position by two elastic cables.
The finger can be printed entirely.
The second adaptive element - spiral spring.
When a finger touches the object the cable movement prvodit to what he is bent and covers the object.
Force is a small and diameter of the spiral spring remains practically unchanged.
Spring only rotates together with the main shaft. After bending the further movement of the cable causes a decrease
in the diameter of the spring and a proportional increase in forces of the holding object.
If the finger is not touched with the object, the second degree of freedom is not used.
Each finger may have an individual movement and the force according to the shape of the object.
The idea worked out on the concept level. It requires further improvement and production preparation.