Pedundulatory robotic locomotion: Centipede and polychaete modes in unstructured substrates

Abstract

Abstract-The present paper considers a novel class of robotic systems, termed pedundulatory locomotors, which can be thought of as undulatory robots augmented by multiple pairs of lateral paddle-like appendages ("parapodia"). Bioinspired strategies for synchronizing the movement of the parapodia with the body undulations, emulating organisms like the centipedes and the polychaete worms, are presented, giving rise to distinct pedundulatory modes. These modes are investigated and comparatively assessed, both in simulation and via experiments with the Nereisbot prototype locomoting on sand and on several other unstructured substrates. Our studies demonstrate the rich gait repertoire and enhanced performance of pedundulatory systems, compared to purely undulatory ones.

Undulatory and pedundulatory robotic locomotion via direct and retrograde body waves

“…Appropriate coordination is required, in order to ensure the positive contribution of the parapodia in thrust generation during each locomotion cycle. Two main such pedundulatory modes have been developed [9], [10], which are inspired by the locomotion of centipedes (for retrograde wave propagation) and of polychaete marine worms (for direct wave propagation). Note that, due to its mechanical design, our system ( Fig.…”

“…More details on the mechanism's kinematics for the proposed pedundulatory modes are available in [10].…”

“…The proposed undulatory and pedundulatory locomotion strategies are investigated experimentally with the Nereisbot robotic prototype [9], [10]. This comprises five body segments, each equipped with a pair of parapodial appendages, providing a total of 14 independently-controlled degrees-offreedom (corresponding to 4 body joints and 10 parapodial joints).…”

“…Their shape allows efficient penetration of granular substrates, with a nominal effective area (estimated at ∼1280mm 2 ) about 2.4 times that of the parapodia employed in [9]. A special instrumented parapodium unit has also been developed [9], [10], which incorporates strain gauges for measuring the normal component F P j N of the force generated by the paddling parapodial motions (see Fig. 6b).…”

“…When crawling over granular substrates on the body segments' flat underside, forward undulatory propulsion of Nereisbot is obtained via tail-to-head body waves [9], [10]. The characteristics of the robot's frictional interaction with the locomotion environment (and hence the propulsive mode and/or performance) may be altered by attaching different modules on the underside of the body segments.…”