Bat Bot 2.0: bio-inspired anisotropic skin, passive wrist joints, and redesigned flapping mechanism

Bat flight has been an underdeveloped area of bioinspired robotics because of the vast complexities of biological bat flight and the over 40 degrees of freedom present in their bodies. The robotic flapping system Bat Bot (B2) has been shown to exhibit fundamental properties of biological bat flight with its articulated wings, its deformable membrane, and its controllable hindlimbs. However, the system is limited in performance by its relatively large mass for the thrust it produces. In an effort to further pursue this important area of flapping flight, we have made several important hardware improvements to the system based on biological inspiration. These include passive wrist joints to reduce negative lift in the upstroke and a novel elastic fiber membrane to mimic the anistropic nature of bat skin for performance and durability. The redesigned flapping mechanism and structure have reduced the weight by 22%, increased the flapping amplitude, lowered mechanical slackness, and improved mass distribution. These hardware improvements are functional together in free-flight tests. This new system Bat Bot 2.0 (B2.0) provides insights into the important elements of design of bat robots, and it brings the goal of complex bat flight maneuvers closer to reality.