GhostBot

Aquariums are soothing miniature ecosystems sustaining aquatic life and, at times, can be a source of inspiration, such as it was for the creator of the GhostBot.

Crafted as a robotic replica of the black ghost knifefish (Apteronotus albifrons) indigenous to South American waters and to Malcom MacIver's aquarium, this mechanical system offers new avenues of scientific investigation.

MacIver is an associate professor of mechanical and biomedical engineering at Northwestern McCormick School of Engineering and Applied Science. He and his research team developed the plans for this robotic fish. Working with Kinea Design, a firm founded by Northwestern faculty, they developed a robot featuring a lycra-covered fin equipped with 32 motors controlling 32 artificial fin rays for the bargain price of $150,000.

Following the scientific method, the researchers tested their robotic creation in George Lauder's water-flow tunnel at Harvard University. It passed the functionality test swimmingly and the developers continue to work on fine tuning its maneuverability, particularly its ability to perform 180 degree rolls in order to make rapid directional changes.

"On the propulsion side, it's a complex system," said MacIver. "The degrees of freedom describe how many ways it can move. GhostBot has 32 degrees of freedom. Every time you add a degree of freedom, you add a degree of complexity. A challenge is developing the control algorithms so that the robot does what you expect."

Thanks to the highly complex propulsion system, the GhostBot is agile as it maneuvers its way with knifelike precision movements in any direction or orientation: backward, forward, vertically and horizontally. The GhostBot will hunt, but not for prey. Its mission will be to detect and identify underwater issues. Whether it's a mechanical malfunction in a pipeline, monitoring invasive species or investigating detrimental practices to the aquatic environment, this robotic fish could be on the case. By swimming like a fish rather than a machine, a future version of the GhostBot will be able to maneuver around delicate environments, such as coral reefs, without inflicting damage. It is also designed to hover to observe phenomenon or rapidly alter swimming speeds.

"If we took these high agility vehicles, equipped them with high resolution optical cameras or with a sampling method, like a small mechanical arm, imagine what it could do," MacIver said. "Imagine taking several to a large reef, sending them out and having them collect information over a certain amount of time, as opposed to dispatching divers, which is a limiting process in terms of time and money."

They are working on the fifth generation of GhostBot trying to refine its sensory and response systems. MacIver says the GhostBot still needs a few more generations before it is ready to patrol the reefs. "We still need to give it ways of sensing the world. We may use electrosense, or a weak electric field, which is what the ghost knifefish uses for sensing. We're one of the first groups in the world to get an engineered version of that working." Keep an eye on the reef, for in the coming years this innovative approach to robotics may play a key role in conservation.


MacIver Lab Website