Meeting Abstract

10.3  Tuesday, Jan. 4  Measuring performance associated with increasing kinematic complexity in a robotic bat wing. BAHLMAN, Joseph W*; SWARTZ, Sharon M; BREUER, Kenneth S; Brown University, Providence, RI; Brown University, Providence, RI; Brown University, Providence, RI joseph_bahlman@brown.edu

Bats are dynamic flyers that have wings derived from primitive mammalian forelimbs. Because bats retain most of the bones and joints of the ancestral mammal limb, their wings contain more than 22 active joints. The many degrees of freedom associated with these joints allows the animals to move their wings through a wide variety of kinematic motions, and these motions influence aerodynamic performance. In this study we seek to understand the performance effect associated with the number of active degrees of freedom and therefore the effect of increasing kinematic complexity. To address this, we have constructed a robotic bat wing, with 7 joints actuated by 3 servo motors. This flapper design allowed the shoulder to move dorso-ventrally and anterio-posteriorally, and the elbow and wrist to flex and extend simultaneously which retracts and extends the entire wing. We systematically increased the number of active joints, allowing the wing to transition from one to three degrees of freedom, and varied the following kinematic variables: wing beat frequency, amplitude, stroke plane, and retraction/extension. For each combination of variables we recorded performance, quantified as lift and drag forces measured using a load cell, and the power required to actuate the wing, measured as the power consumed by the motor. These results are discussed and related to different ecological and behavioral traits displayed amongst different bat species observed in nature.