title: Hybrid parameter identification of a multi-modal underwater soft robot.
abstract: We introduce an octopus-inspired, underwater, soft-bodied robot capable of performing waterborne pulsed-jet propulsion and benthic legged-locomotion. This vehicle consists for as much as 80% of its volume of rubber-like materials so that structural flexibility is exploited as a key element during both modes of locomotion. The high bodily softness, the unconventional morphology and the non-stationary nature of its propulsion mechanisms require dynamic characterization of this robot to be dealt with by ad hoc techniques. We perform parameter identification by resorting to a hybrid optimization approach where the characterization of the dual ambulatory strategies of the robot is performed in a segregated fashion. A least squares-based method coupled with a genetic algorithm-based method is employed for the swimming and the crawling phases, respectively. The outcomes bring evidence that compartmentalized parameter identification represents a viable protocol for multi-modal vehicles characterization. However, the use of static thrust recordings as the input signal in the dynamic determination of shape-changing self-propelled vehicles is responsible for the critical underestimation of the quadratic drag coefficient.
authors.affiliation: Fluid Structure Interaction Research Group, University of Southampton, Southampton SO16 7QL, United Kingdom.
authors.forename: F
authors.initials: F
authors.lastname: Giorgio-Serchi
authors.forename: A
authors.initials: A
authors.lastname: Arienti
authors.forename: F
authors.initials: F
authors.lastname: Corucci
authors.forename: M
authors.initials: M
authors.lastname: Giorelli
authors.forename: C
authors.initials: C
authors.lastname: Laschi
mesh_terms: D000465:Algorithms; D000818:Animals; D040761:Biomimetic Materials; D032701:Biomimetics; D003198:Computer Simulation; D004867:Equipment Design; D016018:Least-Squares Analysis; D049831:Octopodiformes / Q000033:anatomy & histology / Q000502:physiology*; D012371:Robotics; D013550:Swimming / Q000502:physiology*