  We present the design and experimental results of the first 1-DOF,
hip-actuated bipedal robot. While passive dynamic walking is simple by nature,
many existing bipeds inspired by this form of walking are complex in control,
mechanical design, or both. Our design using only two rigid bodies connected by
a single motor aims to enable exploration of walking at smaller sizes where
more complex designs cannot be constructed. The walker, "Mugatu", is
self-contained and autonomous, open-loop stable over a range of input
parameters, able to stop and start from standing, and able to control its
heading left and right. We analyze the mechanical design and distill down a set
of design rules that enable these behaviors. Experimental evaluations measure
speed, energy consumption, and steering.
