Semi-autonomous rover operations: An integrated hardware and software approach for more capable mars rover missions

Abstract—The SRO project is using the 25 kg solar powered SR2 rover to explore rover solutions for long distance Mars missions. The SR2 rover is autonomous rover prototype that has been involved in a number of extended field tests involving Mars-like terrain. The four-wheeled rover uses only two motors for mobility (versus the 10+ used on the Pathfinder and MER rovers). Despite the drastic reduction in actuators, the mobility of SR2 is, by most measures, comparable to that of the rocker-bogie designs. The few areas where it is less capable can almost always be overcome by following some simple rules which have been incorporated into the robot’s software. The reduction in actuators greatly simplifies the onboard real-time software, and can simplify operations as well. During the majority of any traverse, when the robot is on relatively clear ground, the SR2 system is much more power efficient than a rocker-bogie, again improving range and simplifying operations. The real-time software likewise is following a simplified, highly reactive approach. The rover is left on its own to make its way between way-points that are spaced, on average, about 50 m apart. The rover is given 10s of way-points to cover on its own between communication cycles. While the path followed by the robot between way-points may not be as optimal as one planned out on the ground, the increased time spent actually roving more than makes up for this. In tests at the Tule Wash field site (near Salton Sea, California), the rover would regularly make 300m/hr of progress toward the goal (the actual distance traveled, with detours, might have been 20 % longer), allowing distances on the order of a km/day easily reachable. This rover capability enables a lower cost mission architec-ture that provides access to specific points on the surface of Mars