Biorobotic Waterfowl Flipper with Skeletal Skins in a Computational Framework: Kinematic Conformation and Hydrodynamic Analysis

Abstract

Cormorants (Phalacrocoraxe), types of aquatic birds, utilize the compliance/flexibility of the flippers and exploit hydrodynamic/biomechanic processes to accomplish diverse operations. Particularly, the flipper‐propelled locomotion exhibits traits such as super‐redundancy and large deformations, necessitating depiction of both movements of the rigid skeletons as well as local deformations of the soft tissues. However, there are few well‐established kinematic/hydrodynamic framework models and constitutive equations for such rigid–flexible intrinsically coupled biosystems. Herein, combined with a skeletal skinning algorithm to handle the deformation of a flexible body attached to a rigid body, a numerical computation framework for an in‐depth fluid–structure interaction is presented, which enables the capture of viscoelastic and anisotropic characteristics of a highly compliant 3D rigid–flexible coupled model in a low‐Reynolds‐number flow. Considering the biorobotic cormorant flipper with a nonuniformly distributed stiffness as a representative, the challenging issue of controlling a biomechanically compliant flipper to synthesize realistic locomotion sequences, including rigid skeleton movements and soft tissue deformations, is addressed. Furthermore, a numerical computational hydrodynamic analysis is performed to demonstrate that the cormorant flipper can generate 5 N fluid force and 0.45 N m fluid moment during the turning operation in 0.8 s, which is consistent with the former experimental results.

Universal optimal design in the vertebrate limb pattern and lessons for bioinspired design

“…Each of these functions is currently of interest to designers of bioinspired systems. Recent examples of bioinspired limbs for the different applications considered in this paper include robotic arms [6], robotic flippers [7], robotic wings [8], robotic legs [9] and robotic leaping legs [10].…”

The hydrodynamic performance of duck feet for submerged swimming resembles oars rather than delta-wings

“…Consequently, the faster moving and broader base of the trailing edge affects a greater mass of water thus generating most of the drag used as propulsive force 18 , 19 . The hydrodynamics of the avian webbed foot has been previously studied with respect to drag-based vortex formation on rigid plates 20 or as a flexible flipper 21 , 22 for biomimetic surface swimming, hydroplaning and takeoff from water 23 – 26 . However, the hydrodynamic functioning of the foot while swimming underwater should differ from these conditions at the water surface due to differences in paddling kinematics, body orientation and the need to resist buoyancy when the body is entirely submerged.…”