  Among small-scale mobile robots, multi-modal locomotion can help compensate
for limited actuator capabilities. However, supporting multiple locomotion
modes or gaits in small terrestrial robots typically requires complex designs
with low locomotion efficiency. In this work, legged and rolling gaits are
achieved by a 10~cm robot having just two degrees of freedom (DoF). This is
acheived by leg shaping that facilitates whole body rolling and event-driven
control that maintains motion using simple inertial sensor measurements. Speeds
of approximately 0.4 and 2.2 body lengths per second are achieved in legged and
rolling modes, respectively, with low cost of transport. The proposed design
approach and control techniques may aid in design of further miniaturized
robots reliant on transducers with small range-of-motion.
