Autonomous robots and vehicles must occasionally recover from locomotion failure in loosely consolidated granular terrain. Recent mobility challenges led NASA Johnson Space Center to develop a prototype robotic lunar rover Resource Prospector 15 (RP15) capable of wheeled, legged, and crawling behavior. To systematically understand the terradynamic performance of such a device, we developed a scaled-down rover robot and studied its locomotion on slopes of dry and wet granular media. Addition of a cyclic-legged gait to the robot’s wheel spinning action changes the robot dynamics from that of a wheeled vehicle to a locomotor paddling through frictional fluid. Granular drag force measurements and modified resistive force theory facilitate modeling of such dynamics. A peculiar gait strategy that agitates and cyclically reflows grains under the robot allows it to “swim” up loosely consolidated hills. Whereas substrate disturbance typically hinders locomotion in granular media, the multimode design of RP15 and a diversity of possible gaits facilitate formation of self-organized localized frictional fluids that enable effective robust transport.

自治的机器人和车辆有时必须在松散固结的粒状地形中从运动故障中恢复。由于最近的机动性挑战，美国国家航空航天局约翰逊航天中心开发了一种原型的月球漫游车Resource Prospector 15（RP15），该机器人具有轮式，腿式和爬行行为。为了系统地了解此类设备的地形动力学性能，我们开发了按比例缩小的漫游者机器人，并研究了其在干，湿颗粒介质上的运动。在机器人的车轮旋转动作中增加了腿式步态，将机器人的动力从轮式车辆改变为通过摩擦流体进行划桨的运动。颗粒阻力测量和改进的阻力理论促进了这种动力学的建模。一种奇特的步态策略，可搅拌并周期性地使机器人下的谷物回流，从而使其能够“游动”松散固结的丘陵。基质干扰通常会阻碍颗粒介质中的运动，而RP15的多模设计和多种可能的步态则有助于形成自组织的局部摩擦流体，从而实现有效的稳健运输。