Meeting Abstract
From the long necks of giraffes and hyenas, to the large tails of crocodilians, terrestrial animals display a broad diversity of body plans. Additionally, ecological situations such as the carrying of prey, caudal autotomy, offspring, undigested food, or pregnancy will each affect the distribution of mass. We seek to gain insight into how animals may use cranio-caudal mass redistribution to reject disturbances as they navigate uneven terrain. To do so, we have performed experiments using a robophysical model with adjustable mass distribution. In our biorobotic experiment, weights equal to 10% total mass are placed on elastic suspensions at varying distances, simulating the effect of ‘head’ or ‘tail’-biased mass distribution. The performance of the robot traversing an obstacle is then recorded in a variety of configurations, including both legged locomotion with compliant whegs, highly damped airless tires, and wheels. The accumulated results of 126 trials indicate that massive passive tails (without ground contact) can have a destabilizing effect, while head mass enhances traction and suppresses perturbation in many cases. Based on this, the experiment is being expanded to appendages with an active response, moving mass and increasing inertia in response to sensing. Preliminary results from the pilot study suggest active modulation in anticipation of an obstacle, such as a hurdle, will control body attitude, resulting in reduction of undesired oscillations with respect to the cranio-caudal axis (body pitch). This study shows the advantages of mass redistribution in dynamic locomotion, and offers insight into the diversity of evolved body plans, and the use of robophysical models as instruments of discovery.
