Friday, February 10, 2012

1 day prototype: Shifting hull (robot snake)

This is a one day protoype for the Protei project ( Made at the Eindhoven Universitiy of Technology (faculty of Industrial Design).
Movie by: Pieter Bron

The Idea
With this prototype, we wanted to explore the shape changing hull as it was introduced in earlier Protei boats. To do this we decided to build a hull that moves its body like a snake. The hull is made of foam and its movement is controlled by servos attached to an arduino.

Parts list:
Steel rods
Elastic bands
Servos + wiring

We constructed six equal pieces of foam for the snake’s body, a head and tail where also added.
As shown in the sketch below, the servos are placed in a mirrored pattern.This was done for better weight distribution and it was easier create snake-like behaviour.

With a scalpel, holes for the servos where made;

Then a hole was made in every segment through which an elastic band was fed. This band keeps all segments together. In the back and front the elastic band is held in place by a rod that is pierced through the band.

For the joints, we tried different things;

First we tried making the joints form soft foam, this turned out to be to flexible. The joint being to flexible caused the snake to bend also in different directions as it should.

In version 1 of the prototype (see movie) we used square joints made of the same hard foam as the rest of the body is made of. These joints worked better but made the movement of the snake a lot less smooth. Therefore we chose to use triangular joints (version 2 in the movie).

From this prototype we learned about the mechanical properties a shifting hull needs (the importance of the joints)
If we are going to use this technique in the future we should look into using less servos to make a complete body move (with energy efficiency and simplicity in mind).

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