Engineers at Agility Robotics introduces the world’s most stable bipedal robot – Cassie.
Andy Abate, responsible for the mechanical design of Cassie, said that he was thinking of a scenario while helping build the robot – a structure is burning and there’s no way to check if there’s anyone left inside other than sending one of the firefighters in for confirmation. Operations like this are dangerous and risking one life to ensure another’s safety is a price too steep to afford. This inspired the whole team to build an expendable robot which can be sent, instead of humans, in life-threatening situations.
Bipedal robots already exist but they require large amounts of power to even move a few meters. Moreover, even small disturbances in their surroundings can push them off track or topple them over. Cassie is nothing like these and none is yet able to stand eye-to-eye with its exceptional bipedal engineering.
ATRIAS, the prototype bipedal robot where Cassie was based on, was designed for investigating the science behind human walking and running. They tested various concepts to achieve the most effective locomotion solution to enable the robot to move over rough terrain.
Each of ATRIAS’ legs is composed of a 4-bar linkage arranged in a diamond shape. The robot uses a “spring-mass” system which enables the legs to do a pogo-like springing motion to move forward and backward. This structure enables the robot to move through light obstacles and quickly recover from missteps.
However, aside from ATRIAS’ heavy frame and bulky electronics, they found some flaws in its engineering which left it drawing more power for internal operation rather than spending it to do real work. This led them to develop Cassie. The team successfully extracted the data they need from the ATRIAS experiment and used it on Cassie, improving upon the milestones achieved with the former.
One of the most significant changes between ATRIAS and Cassie is their leg shapes – Cassie simulates that of an ostrich’s for improved agility and mobile stability. This inventive configuration enhanced the locomotive capabilities and added natural gait to its movement.
The team custom-designed rotors and some circuitry for Cassie because off-the-shelf components weren’t able to execute the things they wanted the new model to achieve. They also added a few motors to increase movement freedom, allowing Cassie to crouch, squat, sit down, and stand in place. The hips were redesigned to enable the robot to move sideways and also rotate its legs around.
Perhaps one of the biggest improvements Cassie possesses over ATRIAS is its ability to stand still without falling out of balance. ATRIAS used to jog in place to maintain its upright position when it’s not moving forward or backward, spending unnecessary power.
Jonathan Hurst, co-founder of Agility Robotics, said that there are many applications which can benefit from a perfectly engineered bipedal leg. Aside from search and rescue missions, these robotic legs can be used to power up prosthetic limbs and exoskeletons to allow disabled people to walk again. For now, they plan to test Cassie as a courier for package delivery.
According to Agility Robotics’ official website, Cassie has been released to the public just this February 2017.