Today, Agility Robotics, a spin-off of Oregon State University, is officially announcing a shiny new bipedal robot named Cassie. Cassie is a dynamic walker, meaning that it walks much more like humans do than most of the carefully plodding bipedal robots we’re used to seeing. This makes it better at handling the kind of diverse and complex terrain that we walk over all the time without even thinking, a talent that’s going to be mandatory for robots that want to tackle the different environments and situations that they’ll need to master to be actually useful around people.
In addition to search-and-rescue and disaster relief, Agility Robotics has one particular environment and situation in mind: They want Cassie to be scampering up your steps to deliver packages to your front door.
Cassie is just 3 months old in this video, which, if you consider the typical pace for teaching a bipedal robot you designed from the ground up from scratch to walk without constantly falling over, is quite frankly astonishing. As you can see in the video, they’re not being shy with what they ask Cassie to do: It’s on dirt, it’s on grass, it’s balancing on a wobbly dock surrounded by an alarming amount of water, it’s even standing outside in the rain, which is an important feature for any robot that spends much time in Oregon.
And if Cassie looks a bit more like an ostrich than a human, it wasn’t because Agility Robotics was specifically trying for an ostrichlike robot: They don’t want to necessarily mimic the morphology of animals, although they do study animal behavior and dynamics for inspiration and insights. So while ground-running birds may have had the idea first, Agility Robotics intelligently designed Cassie to be agile, efficient, and robust, and this is the leg that they came up with.
This is apparently a required test for legged robots.Image: Agility Robotics via YouTube
Agility Robotics may be a new company, but it’s made up of the folks behind the ATRIAS robots, including MARLO at the University of Michigan, in Ann Arbor. Cassie is the next-generation robot that’s intended to take everything that was learned from the ATRIAS project and build it into a platform that’s both more capable and more practical, as Agility Robotics’ cofounder (and OSU professor) Jonathan Hurst tells us:
There were many, many unknowns in the design of ATRIAS. ATRIAS was the first machine to demonstrate human-like gait dynamics and implement spring-mass walking [reproducing the ground reaction forces and center-of-mass motion of human walking], but it was not a practical machine for any use other than science demonstration.
We learned a few key things with ATRIAS: First, the legs on ATRIAS are configured as a 4-bar linkage, in part to create minimum inertia for the spring-mass model embodiment. However, the configuration results in one motor acting as a brake on the other, with a lot of power cycling internally between motors rather than doing work on the world. After some analysis, we developed the specific leg configuration of Cassie. This allows the motors to be smaller, and the robot to be far more efficient than even ATRIAS was.
Cassie has a 3-degrees-of-freedom hip, allowing it to move its legs forward and backward, side to side, and also rotate them at the same time. And with powered ankles, it can stand in place without having to constantly move its feet.Photo: Agility Robotics
In addition to increased efficiency, Cassie has all kinds of other practical improvements over ATRIAS. It has a 3-degrees-of-freedom hip like humans do, allowing the robot to move its legs forward and backward, side to side, and also rotate them at the same time. This makes Cassie steerable in a way that ATRIAS wasn’t. It also has powered ankles, which it uses to stand in place without having to constantly move its feet the way ATRIAS does, and it has enough battery power to run some beefy onboard computers, meaning that integrated perception is now an option.
University of Michigan engineering professor Jessy Grizzle, who wrangles the ATRIAS robot named MARLO at the Dynamic Legged Locomotion Lab, is getting one of the first Cassie robots, and both he (and his students, who have the thankless job of making sure that MARLO doesn’t faceplant during their outdoor tests) are particularly excited about how durable Cassie is. “Cassie is tough,” Grizzle tells us. “It’s designed for the rough and tumble life of an experimental robot. In principle, we should not have to use a safety gantry of any kind. This will allow us to take the robot into wild places.”
Meanwhile, Agility Robotics is already looking beyond research toward commercial applications for Cassie, Hurst tells us:
If we really understood how to implement dynamically capable legs, there would be so many applications for them, including search-and-rescue, exoskeletons, powered prosthetic limbs, and package delivery.
I believe legged locomotion is going to be analogous to the automotive industry, in terms of size and how it transforms our society. We all want telepresence robots; we all want robots that can help us in our homes. We all want groceries and other goods delivered to our homes on a moment’s notice and for insignificant cost. We all want the cost of manufactured goods to be significantly reduced through more efficient logistics throughout the manufacturing process. Cassie is a step in this direction: It is a first product that will initially be sold to research institutions to support a community of researchers solving the problem of locomotion in the human environment, and Cassie will continue to improve and evolve, as Agility Robotics focuses on products and commercial customers.
A rendering of Cassie’s final design, with protective covers.Image: Agility Robotics
Hurst tells us that arms and sensors are coming soon, which will enable Cassie to get up by itself after a fall, and they’re also working on VR-style telepresence. In terms of cost, Agility Robotics wouldn’t disclose specific numbers, saying only that their goal is to end up with sub-$100K robots.
The company says the initial Cassie production run is already completely sold out, but if you want one to play with, more will be available later in the summer. As far as using Cassie to deliver packages, it’s a compelling idea, and we can see the benefits: In a world where so much of our spaces are designed around bipedal mobility, a bipedal robot could become the easiest and most reliable platform to do anything practical. Cassie has some work to do before it’s ready to be hauling groceries upstairs for you, but we’re very much looking forward to watching this robot taking more steps toward robust and dynamic legged locomotion.
[ Agility Robotics ]
Evan Ackerman is a senior editor at IEEE Spectrum. Since 2007, he has written over 6,000 articles on robotics and technology. He has a degree in Martian geology and is excellent at playing bagpipes.