Why build this?

The motivation behind this project was the robotic hand stand for the Battlebots trophy (known as the "Giant Nut"). I was very impressed with the synchronized movement of all those servo motors! That stuck in my mind… definitely something I needed to try.

Robotic hand creator YouTube video: https://www.youtube.com/watch?v=EfQ6ygf7QE4 and https://www.youtube.com/watch?v=TyQDQ0ad4dA

So I recently decided to create my (simplified) version.

The mechanics

Each "finger" was made with three servo motors, and additional Lynxmotion SES V2 brackets (as listed). The fingers were mounted on a piece of MDF (approximately 30x30cm), which is heavy and helps to keep everything in place.

Electronics

All servo motors are connected to the LSS Adapter, and the LSS Adapter is stacked on a DFRduino UNO (Arduino compatible board).

These smart servo motors (Lynxmotion LSS ST1) are very convenient for a number of reasons, including that fewer wires are needed as they can be daisy-chained.

Also very convenient is the LSS Adapter which has an XT60 connector, so I can power everything directly with a 3s 11.1V Li-ion battery... so the final look is very clean.

Programming/Code

The code was written in the Arduino IDE itself and is actually quite simple (it has the same code base as my mechDOG robot dog).

The movements you see in the video are a "sequence" of "frames". Each frame has its "target positions". What the code does is calculate the difference between the new target position and the previous position, and divide it into small increments.

Conclusion

A synchronized movement involving 15 servo motors and several complex positions is really quite a challenge. You can see in the video that the movements have a little inaccuracy, mainly due to small difficulties in simulating the target positions that I haven't had time to correct yet, and also due to limitations in the code itself (which is quite simple).

But overall it was a lot of fun and a way to learn something new.