Aquatic Swimming of a Multi-functional Pedundulatory Bio-Robotic Locomotor

This paper considers aquatic swimming of a pedundulatory bio-robotic system, inspired by the outstanding aquatic and terrestrial locomotion capabilities of the polychaete annelid marine worms. The robot employs lateral undulations of its elongated body, augmented by the oscillation of active lateral appendages (parapodia), to propel itself. The efficient propulsion and terrain adaptability of such robots on unstructured terrestrial substrates have been demonstrated in previous work. Here, we explore gait generation for underwater propulsion by direct (tail-to-head) lateral body waves, either alone (undulatory modes) or combined with appropriately coordinated parapodial motion (pedundulatory modes). A three-segment compliant-body robotic prototype is used, whose body was fabricated by molding polyurethane elastomers. This robot was tested in a laboratory water tank, to demonstrate the advantage gained from the exploitation of both tail-to-head body undulations and parapodia for underwater swimming. The forward speed may more than double and the propulsive force may increase ten-fold, compared to the case where only undulations are used.