shape sensor can be used with a prosthetic hand

[minumathaly]

I am making a prosthetic hand for a competition. For that i have to solve a task with that hand. The task is to identify 3 shapes(square, cylinder and ball) with out seeing that. The size of the items will be in between 50 to 60mm for the side or as the diameter. As per the rule i cannot use a camera. Is there any sensor to identify all these shapes. The sensor should be firmly attachable to the hand without disturbing the normal activities of the hand.
Also i wish to know the commonly used motors for prosthetic hand. Wish to give the hand to an amputee after the competition. so it should be as accurate as possible

 

[kripacharya]

Here

 

[BradtheRad]

I picture a grid of switches, packed densely so that at least one switch is pressed by a corner of a square when the hand squeezes it.
* Therefore if only 3 or 4 switches turn on, then it tells you it's a square. (Plus maybe a few switches in a row between corners.)
* The ball presses a majority of switches.
* The cylinder presses a large rectangular area. In addition possibly a disk-shaped area or portion of a disk.



A grid of membrane switches could give it flexibility. Several switches in a row could be installed on fingers.