Extending and Bending Robotic Limbs Using Tape Springs for Mobility and Manipulation: Preliminary Investigations

Abstract Conventional mobile robots have difficulty navigating highly unstructured spaces such as caves. In these environments, an extendable/retractable mechanism could be useful for deploying hooks to climb over terrain, or for reaching hard-to-access sites for sample collection. Spooled tape spring mechanisms offer long reach in a compact package, but have not been widely explored for use in mobility and manipulation tasks. This paper proposes a new form of multimodal mobile robot that utilizes a novel tape spring limb named EEMMMa (Elastic Extending Mechanism for Mobility and Manipulation). For mobility, the limb can extend prismatically to deploy grappling hook anchors to suspend and transport the main body, or even serve as legs. For manipulation, the limb can morph its shape to bend around or over obstacles and extend to reach into tight spaces. This can allow the limb to retrieve distant objects, position cameras around corners, or place grappling anchors above an overhang such as a table or cliff. The EEMMMa-1 prototype detailed in this paper can climb ladders and shelves, and exhibit shape morphing to bend over obstacles. The extendable limb uses a simple braking function as a mechanical multiplexer, which can change the limb’s kinematics to control a second rotational DOF using only a single motor. The paper concludes by detailing potential applications and configurations of future EEMMMa robotic systems.