Slope Descent using Plowing to Minimize Slip for Planetary Rovers

Abstract

Steep slopes of unconsolidated material at planetary destinations of recent interest, such as craters and skylights, defy descent by rovers due to uncontrolled slip. This work proposes a novel method based on braking by plowing to arrest slip during descent maneuvers on planetary terrains. The method covers two fundamental maneuvers: direct descent and point-turning. For direct descent, an automatic control system estimates slip through visual odometry and actuates a plow accordingly. For point-turning, the plow is engaged as a point of rotation. Experimental results showed that the slip control system for direct descent kept slip within ±5% for slopes as steep as 31° and for different commanded driving speeds. In the point-turning tests, downhill displacement was less than 0.08 m on inclinations up to 30°. Thus, a plowing policy was developed that allows precise descent on extreme slopes by minimizing slip. As a result, this work expands current rover mobility and control capabilities.