Power and energy consumption of skid-steer rovers turning on loose soil

This study highlights two key phenomena affecting power and energy consumption of skid-steer rovers on loose soil that is not present on the hard ground: soil excavation due to wheel counterrotation and impeded turning when dragging a braked wheel. Experiments in the field and in a controlled laboratory sandbox show that, on sand, power peaks by 15%-20% in a newly identified range of turns with radii between half the rover width, B/2, to R ', the radius at which the inner wheel does not turn. In this range of turns, the inner wheels rotate backwards but are being dragged forward through piles of sand they excavate by counterrotation. At R ', turns are shown to take much longer, leading to higher total energy consumption over time. Experiments in a controlled laboratory sandbox isolate the high motor torque and the resistance force experienced when a skid-steer rover drags a counterrotating or braked wheel, respectively, through loose soil. Other field experiments also demonstrate that paths combining circular arcs and lines can lead to energy savings of up to 15% relative to common ones consisting of point turns and lines; the experimental results suggest the circular arcs should have radii of approximately 2R '. The quantitative values presented in this paper are specific to the rover and soils tested, but there are reasons to support the overall conclusions generalizing to all skid-steer rovers in loose soil.