M.E.C.H.A.

We created a hand that is able to move all the fingers thanks to 9 servomotors. The hand’s movement is controlled by a tracking system on a computer. We used some fishing line to connect each servo to a finger. 5 servos are used to flex the finger, one for each one. The extension is made by a spring that brings back the finger to its original position.

3D printed fingers, forearm, wrist

39 ball bearings (3x6x10mm)

4 springs (4x10mm)

9 servomotors (MS18)

Binding wire (50x0,7mm)

Hot glue

Arduino UNO R3

Jumpers

Fishing line

Breadboard

String (2mm diameter)

Elastic

Cardboard

5 brass inserts (2,5x3,2mm)

We studied how fingers work and we started to think how we could track the real hand’s movement. We decided to use a video tracking system because we didn’t want to use any gloves with potentiometers or flex sensors. We also understood how to make the fingers finding an online model on OnShape.

We’ve printed all the finger’s components, with a lot of problems with the smaller pieces because of the printer. We solved that problem by using a better 3D printer.

We tried a lot of different ways to put together the fingers. We used different types of strings, different types of springs and rubber bands. Metal springs worked the best to pull back the fingers in place. We assembled the different parts of the fingers also using bell bearings between the phalanges and brass inserts at the tip of the fingers to keep the fishing line in place.

We organized the servo motors in the forearm because we didn’t have enough space in the palm. We glued them on a cardboard structure to prevent them from moving.

5 of the 9 servomotors were placed in the forearm, the remaining 4 between the fingers.

We also uploaded a schematic of the circuit to help understand it better.

While we were making the hand, we were also coding the program for the Arduino. We tried different ways, but in the end we decided to use a tracking system to control the robotic hand’s movement. With that program the computer’s cam can track the movement of the real hand.

Here is the link to the github page for the code:

https://github.com/norachv822/HAND-TRACKING-SYSTEM-FOR-MECHANICAL-HAND

We attached the hand, the wrist and the forearm with binding wire.