Snout orientation for lift and depth control while burrowing

Researchers continue to study the mechanisms behind controlling and maintaining depth for fossorial robotic locomotion. The sandfish skink (Scincus scincus) has been closely studied to understand its unique morphologies and specialized behaviors that enable burrowing in dry granular media. Maladen et al. (2011) changed the vertical direction of burrowing for a robophysical model with discrete head shapes and demonstrated that the shape and angle of the skink’s snout relative to the horizontal direction are key features for modulating lift forces. We explore continuous snout orientation change using a fixed shape to test whether closed loop trajectory control is achievable. The wedge-like object is fixed to a UR-10 robot with an attached load cell and dragged at low constant horizontal velocity through granular media. First, a wide range of scheduled snout orientations occur while the robot arm controls for zero vertical force, demonstrating achievable vertical trajectories while tracking effects on horizontal drag. We perform this study using shapes of differing internal tip angles. We then attempt feedback control given a target trajectory for the most mobile snout shape. This work provides insight into the development of burrowers with steering capability using shape-changing structures.