This EArly-concept Grant for Exploratory Research (EAGER) project explores the interaction between soft robots and commonly occurring granular media, like sand, soil, or gravel. Soft robots constructed from compliant materials like rubber or cloth are much safer than rigid robots for use with and around people. Soft robots are also remarkable for their ability to use intrinsic structural compliance to passively adapt to unknown and unexpected obstacles and terrain. Yet analyzing the movements of a robot that makes intermittent contact with the ground is difficult even for rigid robots moving on hard surfaces, and much more so when both the robot structure and the terrain may deform in poorly understood ways. Thus, in order to fully realize the potential of soft robots operating reliably and predictably in unknown natural terrain, it is critical to construct a systematic framework for modeling the forces and movements of soft structures moving in or on granular media. This EAGER project creates such a framework in two parts. First is a sequence of tests that measure the forces and deformations associated with a set of standard objects moving in pre-defined patterns through a granular medium. Next, mathematical models are used to capture the essential features of the interaction, which may then be extended to more general motions and geometries. Soft robotics is rapidly emerging as a new field, with the potential to transform applications such as health care, search and rescue, scientific exploration, and orthotics and prosthetics, much as rigid robots revolutionized manufacturing. The results of this project will help advance the national prosperity and welfare, and secure the national defense, for example, by enabling the creation of soft robots that can move reliably through uncertain terrain for search-and-rescue, exploration, environmental monitoring, or construction. The project also supports providing a research experience to undergraduate students through the UC San Diego Summer Training Academy for research Success (STARS) program.
The primary goals of this project are to, 1) develop an experimental system to study the forces and deformation of soft intruders in laboratory granular materials, and 2) develop discrete element method (DEM) and resistive force theory (RFT) models of the interaction between granular material and soft robot appendages. Locomotion of mobile robots is challenged by complex, natural substrates such as sand, leaf-litter, brush, and slopes. Effective movement and control of mobile robots over real-world environments requires study of the failure modes of a model natural substrate granular material. A recent study demonstrated that empirically verified granular models can be used to design and control legged robots for effective locomotion on unstructured terrain. However, this approach has only been demonstrated for rigid intruders. Robots with soft bodies and appendages present new opportunities for robot functionality, including resilience, passive adaptation, and safe interaction. Mobile soft robots have the potential to control the local interactions between complex substrates and soft appendages, and to enable sensing and feedback control of foot stiffness and shape when moving across complex substrates. However, this potential will not be realized without accurate models of the interactions between soft robot appendages and complex, natural substrates. The overarching goal of this one-year project is to enable predictive understanding of how soft intruders interact with granular material to inform soft robot design and control in future applications. These efforts will enable the design and control of future soft robots. Additionally, this work will be of interest to scientists and engineers interested in the flow and failure of granular materials.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
