Search for: All records

Abstract The Multi-terrain Amphibious ARCtic explOrer (MAARCO) rover is an amphibious arctic rover designed to explore arctic regions in otherwise unsafe or restricted environments. The MAARCO rover consists of a propulsion system with two helical drives made up of hollow cylinder ballasts wrapped in auger or screw shaped blades that provide thrust to propel the vehicle as the drives rotate. Computational fluid dynamic methods provide a better understanding of the helical drives properties effects on hydrodynamic forces. In this paper, the computational fluid dynamic simulations are performed in ANSYS Fluent to observe the hydrodynamic properties of a helical drive. The drag and thrust on the helical drives are simulated for various helical drives with different blade heights and pitch lengths to determine general trends and characteristics of helical drives in water to optimize the vehicle’s abilities to navigate underwater. The helical drive drag is simulated using bluff body drag simulations with a prescribed velocity. The helical drive thrust is simulated using a multi-reference frame (MRF) mesh model with a frame motion replicate flow rotating around a stationary helical drive at a prescribed angular velocity. A convergence study was conducted to test different meshes and turbulence models to determine the most accurate drag and thrust simulation methods. The results demonstrate the effects the blade height and pitch length have on the helical drive thrust and drag properties, while maintaining a constant ballast diameter. From these results a helical drive design can be determined to optimize the net force and therefore the overall vehicle performance. 

Abstract Helical drives (sometimes known as Archimedes’ screws) are a class of propulsion mechanism with the potential for application in amphibious, multi-terrain robotic ground vehicles such as Arctic rovers. Despite their simplistic construction, consisting of a screw-like rotating drum with a helically wound blade, their propulsion dynamics are complex and not well understood. There is a need for an experimental testing environment capable of controlling and recording the variables that characterize the dynamics of this terrestrial propulsion mechanism in order to experimentally validate dynamic and energetic modelling. Such variables include displacement, velocity, and acceleration of the mechanism in question in the x, y and z directions, as well as terramechanical properties such as substrate moisture content, subsequent density, and particulate size. This environment would also ideally be designed with modularity in mind in order to easily adapt to multiple different test conditions and terrestrial propulsion mechanisms. This paper describes the design of the experimental testing rig created to serve the above-described purpose. The apparatus is tested with an example of a helical screw drive at three different rover weights. Results of an initial test are shown, and the trends shown in the x position (longitudinal travel), z position (vertical travel), and effective pitch length are discussed.