MEAM Ph.D. Thesis Defense: “No Watts Wasted: Spines and Tails for Agile Legged Locomotion”

Despite considerable advancements in recent years, legged robots still fall short in terms of agility when compared to their animal counterparts. This thesis takes a two pronged approach to creating more agile behaviors by pursuing the intuition that agile legged machines should use much of their available power during agile behaviors.

The first approach leverages hybrid averaging analysis of SLIP like robots to devise a hip-energized control strategy. This controller takes a previously underutilized actuator and applies it to energize the robot. The resulting analysis provides new insight into the role of the hip actuator and symmetry in SLIP-like machines. The second approach seeks to design high power robots with few actuators, which minimizes the framing cost while also making it easier to design behaviors which utilize the available power.

This thesis contributes support for the hypothesis that moving actuators from the legs to a tail or spine provides more opportunities to deploy them for spatial mobility. That support is manifest in the design and control of Jerboa 3.0, a tailed biped featuring a high powered 2 degree of freedom tail whose lavish tail actuation budget comes at the expense of assigning only one motor to each of its springy legs. Jerboa 3.0 is capable of sustained spatial hopping, starting and stopping on command, and getting up again after falling. Lastly this thesis contains a speculative look as to what a simple model for the use of spines and tails for energization might look like. The resulting double-spring double-mass model enables both tail-energized hopping in a tailed robot and spine-energized bounding in a spined quadruped. More broadly the thesis serves as a case study in the creation of more agile legged machines that might one day rival animals.