Undulatory and pedundulatory robotic locomotion via direct and retrograde body waves

Abstract

Abstract-The present paper explores the effect of the mechanism-substrate frictional interface on the locomotion characteristics of robotic mechanisms employing traveling waves for propulsion. For these investigations, an extended class of undulatory robotic locomotors is considered, termed pedundulatory, which augment lateral body undulations by coordinated dorso-ventral oscillations of multiple pairs of lateral paddle-shaped appendages (parapodia). We examine how, the same robotic prototype, allows the implementation of four distinct bio-inspired undulatory and pedundulatory modes of locomotion, by modifying the motion control strategy depending on the mechanism-substrate frictional interface. These modes employ retrograde or direct body waves, either standalone (giving rise to eel-like and ochromonas-like undulatory locomotion modes, respectively), or combined with appropriately coordinated substrate contact by the parapodial appendages (giving rise to centipede-like and polychaete-like pedundulatory modes, respectively). These four modes are investigated and comparatively assessed, both in simulation and via extensive experiments on granular substrates with the Nereisbot prototype. Our results validate the identified locomotion principles and also highlight the enhanced performance and gait repertoire of pedundulatory systems, compared to purely undulatory ones.

Optimizing snake locomotion in the plane

“…We find very clear asymptotic behaviour for U(t), V(t), dR(t)/dt and η, Therefore, zero cost of locomotion does, in fact, arise in the limit of a sequence of smooth shape dynamics. This type of travelling-wave shape dynamics, which yields locomotion in the direction of wave propagation, has been called a 'direct' wave in the context of crawling by snails [31] and worms [32]. A triangular wave motion was previously considered (in less quantitative detail) by Bekker [33].…”

Visual homing for undulatory robotic locomotion

“…It employs the Nereisbot prototype [6], which is a 5-segment robotic platform developed at ICS-FORTH for studying undulatory locomotion as well as pedundulatory extensions thereof, where body undulations are combined with appropriately synchronized movements of leg-like appendages (termed parapodia). Nereisbot can be adapted for locomotion over a wide variety of substrates, both conventional (e.g., hard floors) and unstructured (e.g., sand, pebbles and grass).…”

“…Undulatory prototypes without wheels, which crawl on their underside (see [5], [6] and references therein), or swim (e.g., [3]), are also being developed. The undulatory robotics literature has mainly focused, so far, on mechanical design, modelling and gait generation.…”

Passive dynamic walking of combined rimless wheel and its speeding-up by adjustment of phase difference

“…Various gaits for a modular robot with actuated rotational connections between segments were studied in simulation, with the conclusion that undulatory gaits could be faster than rigid-body gaits [7]. Various undulatory patterns, both with and without legs, were demonstrated in a five-segment robot also with active rotational joints between segments [8]. While centipede robots at larger scales exhibit the use of body undulations to achieve forward locomotion, many do not offer explanations of performance benefits from using undulatory gaits.…”