Aracna is a new, quadruped robot platform which requires non-intuitive motor commands in order to locomote and thus provides an interesting challenge for gait learning algorithms, such as those frequently developed in the Evolutionary Computation and Artificial Life communities. Aracna is an open-source hardware project composed of off-the-shelf and 3D-printed parts, enabling other research teams to modify its design according to their scientific needs.

Design Considerations

Aracna was designed to overcome the shortcomings of a previous quadruped robot platform, whose legs were so heavy that the motors could not reliably execute the commands sent to them. We avoid this problem by locating all motors in the body core instead of on the legs and through a design which enables the servos to have a greater mechanical advantage. Specifically, each of the four legs has two joints controlled by separate four-bar linkage mechanisms that drive the pitch of the hip joint and knee joint. This novel design causes unconventional kinematics, creating an opportunity for gait- learning algorithms, which excel in counter-intuitive design spaces where human engineers tend to underperform.

Code, Drivers, Design Files

All of the code, drivers, and STL files necessary to 3D print your own Aracna are available on GitHub. The Aracna codebase is currently in the process of being rewritten from scratch to improve flexibility and usability.

• The currently under-development python evolutionary host code and embedded code can be found on the official Creative Machines Aracna GitHub Repo. This repo includes code that is presently under development.
• Legacy drivers and code are on the aracna branch of the QuadraTot repository
• Hardware design files and more pictures are in the aracnaHardware repository

Contact Sara Lohman, Jason Yosinski, Jeremy Blum, or Eric Gold with any questions. If you'd like to improve our code, feel free to fork the repository and submit a pull request on GitHub.

3D Printing Aracna

Below is a short video of Aracna being 3D printed on an Objet Connex500 3D printer:

Publications

Read more details and design considerations in our paper, presented at ALife 13:

Other projects at the Cornell Creative Machines Lab

		QuadraTot, a earlier 3D printable robotic platform
		EndlessForms.com, a site where you can evolve your own 3D shapes
		AI vs. AI: Two chatbots talking to each other, a research video that went viral in August 2011