A biomimetic robotic platform to study flight specializations of bats

TLDR

Bats exhibit exceptional agility through highly flexible wings with over 40 active and passive joints, offering insights for biology and aerial robotics but posing significant modeling and control challenges. The authors built a 93‑gram autonomous robot, Bat Bot (B2), to replicate bat wing morphology. B2 uses stretchable silicone membrane wings governed by a reduced set of dominant joints—identified as asynchronous armwing and mediolateral armwing, dorsoventral leg motions—combined with mechanical constraints and a 56‑µm ultrathin skin to emulate bat wing kinematics and elasticity. The robot achieved autonomous flight by applying virtual constraints to control its articulated, morphing wings.

Abstract

Bats have long captured the imaginations of scientists and engineers with their unrivaled agility and maneuvering characteristics, achieved by functionally versatile dynamic wing conformations as well as more than 40 active and passive joints on the wings. Wing flexibility and complex wing kinematics not only bring a unique perspective to research in biology and aerial robotics but also pose substantial technological challenges for robot modeling, design, and control. We have created a fully self-contained, autonomous flying robot that weighs 93 grams, called Bat Bot (B2), to mimic such morphological properties of bat wings. Instead of using a large number of distributed control actuators, we implement highly stretchable silicone-based membrane wings that are controlled at a reduced number of dominant wing joints to best match the morphological characteristics of bat flight. First, the dominant degrees of freedom (DOFs) in the bat flight mechanism are identified and incorporated in B2's design by means of a series of mechanical constraints. These biologically meaningful DOFs include asynchronous and mediolateral movements of the armwings and dorsoventral movements of the legs. Second, the continuous surface and elastic properties of bat skin under wing morphing are realized by an ultrathin (56 micrometers) membranous skin that covers the skeleton of the morphing wings. We have successfully achieved autonomous flight of B2 using a series of virtual constraints to control the articulated, morphing wings.