Rheological Interaction Physics of Wheeled Locomotion in Soft Substrates for Improved Mobility: GT Component
Abstract
When no road is available, wheeled and tracked vehicles often have no choice but to traverse complex terrain. The terrain can have variable slope, cohesion, heterogeneity, and ability to support load, which can impede progress or cause the wheels to become stuck. Off-road engineering and terramechanics supply successful empirical models of wheeled locomotion often applied to large, heavy vehicles. However, recent evidence suggests these models may not be applicable to locomotors that are small and lightweight, such as interplanetary rovers and unmanned ground vehicles. Through an investigation of the rheological interaction of physics between wheels and the substrates underneath, we will develop locomotion control and terrain sensing that can help vehicles traverse loose and/or complex terrain effectively. A fundamental understanding of the vehicle/terrain physical system will inspire improved and physically accurate models of terrain traversal. Achieving reliable motion requires new insight into the general physics of wheeled locomotion in both high and low speed regimes. Many current terramechanics models are empirical and apply to large, slowly moving vehicular systems, and materials like sand and mud are not yet described by complete quantitative models that allow understanding of locomotion in fluids, such as the Navier-Stokes equations. Our group has recently made great progress in developing models for movement in dry granular media. We developed these models, including Resistive Force Theory (RFT) and discrete granular element methods, based on extensive experiments with real granular substrates. Recent results by Ken Kamrin at MIT have supported RFTÕs validity by showing that it is derivable from more general plasticity theory, along with experimentally using RFT to describe wheeled locomotion. These models have had predictive power in discovering optimal locomotion strategies in both robotic and animal specimens in how different gaits and actuations effectively generate movement. Motivated by our success with small locomoting robots and animals analyzed through our granular interaction models, we propose to develop a joint three year program with Kamrin to investigate and discover principles of wheeled locomotion and general intrusion on complex terrain. We will examine the physics arising in vehicular locomotion scenarios involving sloped terrain, wet granular terrain, transient granular inertia, and heterogeneous obstacles. In these experiments, we will vary independent parameters to obtain insight into the rheological dependencies and physical scaling relations in this kind of locomotion. From our results, we will determine the applicability of our rheological interaction models to wheeled locomotion, and refine our models to capture features of the wheel/media interaction. We will also use our experimental results and collaboration with KamrinÕs group to further develop computational tools for rheological modeling, such as Discrete Element and Material Point Methods. Rapid localized granular intrusion experiments and simulation will also give insight into inertial phenomena that occur when a wheel pushes off from rest. Simulations can show the overall flow and response of the media to contact interactions, and help us study how microscopic granular properties influence the macroscopic outcome. Through our collaboration with KamrinÕs group and the joint development new experimental and analytical approaches, we will be able to extend RFTÕs applicability to many more materials and locomotion scenarios.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 08, 2019
- Source ID
- W911NF1810120
Entities
People
- Daniel Goldman
Organizations
- Army Contracting Command
- Georgia Tech Research Corporation
- United States Army