  This paper presents a couple of interesting ideas: a telescopic actuator
design and a bio-inspired sea urchin robot. The "spines" of the sea urchin
robot consist of fourteen telescopic actuators equally distributed over it's
spherical body. The telescopic actuation system integrates linked 3D printed
rack articulations that are locked in all axes if the pinion moves the links in
a forward direction, creating a solid and rigid rack. Thus, the robot is able
to propel and move by extending its spines. On the other hand, if the pinion
moves the rigid articulations backward, these are unlocked and can be folded in
a minimal space, enabling the bionic sea urchin robot to hide its spines inside
its constrained spherical-body and be able to roll. Simulations and experiments
are presented from both, the sea urchin robotic prototype and different scales
of the telescopic actuation system.
