  We present a computational design system that assists users to model,
optimize, and fabricate quad-robots with soft skins.Our system addresses the
challenging task of predicting their physical behavior by fully integrating the
multibody dynamics of the mechanical skeleton and the elastic behavior of the
soft skin. The developed motion control strategy uses an alternating
optimization scheme to avoid expensive full space time-optimization,
interleaving space-time optimization for the skeleton and frame-by-frame
optimization for the full dynamics. The output are motor torques to drive the
robot to achieve a user prescribed motion trajectory.We also provide a
collection of convenient engineering tools and empirical manufacturing guidance
to support the fabrication of the designed quad-robot. We validate the
feasibility of designs generated with our system through physics simulations
and with a physically-fabricated prototype.
