  The Cassie bipedal robot designed by Agility Robotics is providing academics
a common platform for sharing and comparing algorithms for locomotion,
perception, and navigation. This paper focuses on feedback control for standing
and walking using the methods of virtual constraints and gait libraries. The
designed controller was implemented six weeks after the robot arrived at the
University of Michigan and allowed it to stand in place as well as walk over
sidewalks, grass, snow, sand, and burning brush. The controller for standing
also enables the robot to ride a Segway. A model of the Cassie robot has been
placed on GitHub and the controller will also be made open source if the paper
is accepted.
