Bio-inspired Dual-auger Self-burrowing Robots in Granular Media

It has been found that certain biological organisms, such as Erodium seeds and Scincus scincus, are capable of effectively and efficiently burying themselves in soil. Biological Organisms employ various locomotion modes, including coiling and uncoiling motions, asymmetric body twisting, and undulating movements that generate motion waves. The coiling-uncoiling motion drives a seed awn to bury itself like a corkscrew, while sandfish skinks use undulatory swimming, which can be thought of as a 2D version of helical motion. Studying burrowing behavior aims to understand how animals navigate underground, whether in their natural burrows or underground habitats, and to implement this knowledge in solving geotechnical penetration problems. Underground horizontal burrowing is challenging due to overcoming the resistance of interaction forces of granular media to move forward. Inspired by the burrowing behavior of seed-awn and sandfish skink, a horizontal self-burrowing robot is developed. The robot is driven by two augers and stabilized by a fin structure. The robot's burrowing behavior is studied in a laboratory setting. It is found that rotation and propulsive motion along the axis of the auger's helical shape significantly reduce granular media's resistance against horizontal penetration by breaking kinematic symmetry or granular media boundary. Additional thrusting and dragging tests were performed to examine the propulsive and resistive forces and unify the observed burrowing behaviors. The tests revealed that the rotation of an auger not only reduces the resistive force and generates a propulsive force, which is influenced by the auger geometry, rotational speed, and direction. As a result, the burrowing behavior of the robot can be predicted using the geometry-rotation-force relations.Comment: Master's thesis, 62 pages, 40 figures, ProQues

Utilization of Kirigami Skins as a Method of Creating Bespoke Soft Pneumatic Actuators

Soft pneumatic actuators have many applications in robotics and adaptive structures. Traditionally, these actuators have been constructed by wrapping layers of reinforcing helical fibers around an elastomeric tube. This approach is versatile and robust, but it suffers from a critical dis-advantage: cumbersome fabrication procedures. Wrapping long helical filaments around a cylindrical tube requires expensive equipment or excessive manual labor. To address this issue, we propose a new approach towards designing and constructing pneumatic actuators by exploiting the principle of kirigami, the ancient art of paper cutting. More specifically, we use “kirigami skins”—plastic sleeves with carefully arranged slit cuts—to replace the reinforcing helical fibers. This paper presents an initial investigation on a set of linear extension actuators featuring kirigami skins with a uniform array of cross-shaped, orthogonal cuts. When under internal pressurization, the rectangular-shaped facets defined by these cuts can rotate and induce the desired extension motion. Through extensive experiments, we analyze the elastic and plastic deformations of these kirigami skins alone under tension. The results show strongly nonlinear behaviors involving both in-plane facet rotation and out-of-plane buckling. Such a deformation pattern offers valuable insights into the actuator’s performance under pressure. Moreover, both the deformation characteristics and actuation performance are “programmable” by tailoring the cut geometry. A computational model was developed to predict the deformation pattern of the kirigami skins. This study lays down the foundation for constructing more capable Kirigami-skinned soft actuators that can achieve sophisticated motions. Additional design variables were implemented into the kirigami patterns to generate for rectangular and rhomboid elements. A kirigami skin defined by these parameters can produce a wide range of actuation patterns