Design of a Two-Wheeled Rover With Sprawl Ability and Metal Brush Traction

PUFFER (“pop-up flat-folding explorer robot”) is an expendable, two-wheeled NASA/JPL rover that is meant to explore the less-accessible regions of Mars. This paper presents the UC Berkeley prototype of PUFFER that was used to inform the mechanical design of the folding chassis for the ensuing NASA/JPL version. PUFFER is so named because it can fold itself to fit into tight spaces; its chassis consists of a 3-D linkage that can vary the sprawl angle of its wheels. This ability to sprawl, besides letting multiple PUFFERs fit into a parent rover, improves PUFFER’s slope-climbing ability by allowing it to lower its center of mass. To further improve slope climbing, each wheel is fitted out with nitinol brushes that serve to enhance ground traction. Together, these two features allow the Berkeley prototype of PUFFER to climb 47 deg rock inclines that have a surface roughness of about half its folded height. Other qualities of PUFFER are that it has a collapsible tail, is able to flip itself over, and requires only three actuators.