Researchers from the U.S. Army Research Lab created a new robot, named Mini Rover, that can travel over sand-covered hills with ease. Mini Rover is built with wheeled appendages that can be lifted with the potential to survey other planets and even the moon with rear rotator pedaling. Mini Rover climbs using paddling, walking, wheel spinning at the same time thanks to terradynamics.

Built with multifunctional appendages able to spin wheels that can also be wiggled and lifted, a new robot developed at Georgia Tech with U.S. Army funding has complex locomotion techniques robust enough to allow it to climb sand covered hills to avoid getting stuck while surveying a planet or the moon. Source: Christopher Moore, Georgia Tech)

Loose materials, like sand, on a surface flow when touched causing robots to struggle to move across it. With the new developments, robots can transition to wheeled and legged modes to adjust to the surface it is moving across.

The new rover creates a localized fluid hill for the back wheels that is less steep for the real slope to climb across a surface. While moving the robot is essentially creating an easy to climb hill for itself. These movements allowed the team to test many variations of movement with granular drag force and the resistive force theory.

Mini Rover can sweep the surface, spin its wheels and lift its wheeled appendages when needed. This range of motions allows the robots to climb across many surfaces. The four-wheeled appendages are driven by 12 motors.

To test the robot, the team started installed the gaits on the NASA RP15 robot. They experimented with locomotion schemes that were not possible to test on a full-sized rover. They tested on slopes of simulated planetary and lunar hills using a fluidized bed system named Systematic Creation of Arbitrary Terrain and Testing of Exploratory Robots (SCATTER). With SCATTER, robots could be tilted to evaluate the role of controlling the granular substrate.

The new gait allowed the robot to climb a steep slope with the front wheels by stirring up granular material and pushing towards the back wheels. The rear wheels move side to side in a wiggle motion and lift and spin to create a paddling motion. The material pushed back changed the slope that the rear wheels had to climb. The rover made steady progress up a hill that a simple robot could not.

The new robot was created with mechatronic architecture, commercially available components and minimal number of parts. It was used as a lab tool and explore creative experiments without downtime, performance limitations or damaging the rover. The new gait discovery could avoid the mistakes that the Mars Rover made, causing it to get stuck in the sand.

The next step for the researchers is to scale up these abilities for larger robots.

A paper on this research was published in Science Robotics.