2022-10-10 カリフォルニア大学バークレー校(UCB)
Frontiers in Robotics & AIに本日発表された研究で、垂直方向に自己潜行できる最初の脚式ロボットの一つを実証した。この掘削ロボットはEMBUR（EMerita BUrrowing Robot）と呼ばれ、新しいデザインの脚を用いて、太平洋のモグラガニが砂浜に身を埋める方法を模倣した下降動作を実現した。
砂や土のような粒状の媒体の中を下向きに移動することは困難である。動物が深く掘れば掘るほど、粒は強く押し戻され、掘削の妨げになる。
そこで研究グループは、この課題を解決するため、垂直方向に動く穴掘りロボットの脚部に、ある方向と別の方向で大きな力を受ける「異方性力覚」を持たせることにした。水泳のように、このロボットの柔らかい布製の脚は、パワーストロークでは大きな力を受けて広がり、リターンストロークでは折りたたまれて収縮する。
＜関連情報＞
- https://engineering.berkeley.edu/news/2022/10/digging-deep/
- https://www.frontiersin.org/articles/10.3389/frobt.2022.999392/full
モグラガニをモチーフにした垂直自生型
Mole crab-inspired vertical self-burrowing
Laura K. Treers, Benjamin McInroe, Robert J. Full and Hannah S. Stuart
Frontiers in Robotics & AI Published:10 October 2022
DOI:https://doi.org/10.3389/frobt.2022.999392
We present EMBUR—EMerita BUrrowing Robot—the first legged robot inspired by the Pacific mole crab, Emerita analoga, capable of burrowing vertically downward. We choose Emerita analoga as a model organism for its rapid downward burrowing behaviors, as it is four times as fast as the most rapid bivalve mollusk. Vertical burrowing in granular media is a challenging endeavor due to the tendency for the media to create upwards resistive forces on an intruder, even during purely horizontal motions. Our robot is capable of vertically burrowing its body in granular substrate primarily through excavation using two leg pairs, which are functionally analogous to groupings of leg pairs of the mole crab. We implement a novel leg mechanism with a sweeping trajectory, using compliant fabric to enable an anisotropic force response. The maximum resistive force during the power stroke is 6.4 times that of the return stroke. We compare robot body pitch and spatial trajectories with results from biomechanical studies of the mole crabs. We characterize the sensitivity of the robot to initial depth, body pitch and leg pose, and propose bounds on initial conditions which predict various burrowing failure modes. Parametric studies utilizing Granular Resistive Force Theory inform our understanding of robot behavior in response to leg phasing and orientation. Not only does this robotic platform represent the first robophysical model of vertical mole crab-inspired burrowing, it is also one of the first legged, primarily excavative small-scale burrowing agents.
