Effects of Turning Radius on Skid-Steered Wheeled Robot Power Consumption on Loose Soil

This research highlights the need for a new power model for skid-steered wheeled robots driving on loose soil and lays the groundwork to develop such a model. State-of-the-art power modeling assumes hard ground; under typical assumptions this predicts constant power consumption over a range of small turning radii where the inner wheels are rotating backwards. However, experimental results performed both in the field and in a controlled laboratory sandbox show that, on sand, power is not in fact constant with respect to turning radius. Power peaks by 20% in a newly identified range of turns where the inner wheels rotate backwards but are being dragged forward. This range of turning radii spans from half the rover width to R', the radius at which the inner wheel is not commanded to turn. Data shows higher motor torque and wheel sinkage in this range. To progress toward predicting the required power for a skid-steered wheeled robot to maneuver on loose soil, a preliminary version of a two-dimensional slip-sinkage model is proposed, along with a model of the force required to bulldoze the pile of sand that accumulates next to the wheels as it they are skidding. However, this is shown to be a less important factor contributing to the increased power in small-radius turns than the added inner wheel torque induced by dragging these wheels through the piles of sand they excavate by counter-rotation (in the identified range of turns). Finally, since a direct application of a power model is to design energy-efficient paths, time dependency of power consumption is also examined. Experiments show reduced rover angular velocity in sand around turning radii where the inner wheels are not rotated and this leads to the introduction to a new parameter to consider in path planning: angular slip

Introducting the concept of a cybercartographic act: The creation of a cybercartographic atlas

Cybercartography aims to rethink the way we design, use and disseminate maps on the Internet. It represents an interdisciplinary approach combining art and science, technological change and critical perspectives. This original approach is introduced in this paper through the presentation of the genesis of the Cybercartographic Atlas of Antarctica. This presentation illustrates the main characteristics of cybercartographic atlases: multisensory function, interoperability, modularity and ability to evolve. This presentation generates a discussion about the importance of rethinking the cybercartographic artifact as the outcome of a complex and subjective production process. Drawing on similar works done in different fields such as photography, the concept of "cybercartographic act" is then proposed to demonstrate that the artifact is inseparable from the act of which it is the result and that cybermaps could depict this association