Knock-knock! Who is it? It's an ostrich delivering your pizza

The brains behind the bird

Cassie has two internal com­puters. One operates a control loop that is responsible for the lower-order functions--just as the cerebellum in humans and other animals controls posture and balance. The other, which responds to commands from its human controllers for handling all active movement. This might seem complex, but the robot is designed to be user-friendly.

The balancing act

Cassie's motor must be on for it to stand upright; cut the power and it collapses in a heap. Agility Robotics co-founder and CEO Damion Shelton says, "It means there's no built-in mechanical stability to the system, which makes its ability to react to disturbances and unexpected ground positioning really high."

Objects that are top heavy are actually easier to balance, so Cassie is designed with more than 85 percent of its weight above the top joint. The bot's lightweight legs provide a second benefit: Very little energy is required to move them, making the machine quicker to react and more efficient overall.

The beauty of it

Cassie's avian aesthetic isn't exactly by design.  Jonathan Hurst and his team closely studied the ways various animals perambulated, and then created a robot that replicated those mechanics. To create Cassie, the Agility team used Atrias as a sort of a first step, and then performed analyses to improve efficiency.

Yearning to go free

The company's goal is for the bots to operate autonomously--say, in a dangerous industrial environment. For now, Cassie can be run from a laptop--although that's actually technological overkill. "We found out," Shelton was quoted saying, "that you can't engineer a solution that's better than what people use for remote-control airplanes, so we just bought a bunch of those remotes."