The detection of wheel sinkage has great significance for rover mobility optimization control and prevention of wheel sinking. A new wheel sinkage detection method is proposed based on planetary rovers' wheel-soil boundary. The model of wheel sinkage calculation is built. The machine vision method is proposed to extract wheel-soil boundary. Wheel-soil interaction image is processed into binary image, and the wheel-soil boundary is extracted according to its morphological features. The wheel sinkage depth, entrance angle and departure angle are calculated through the model of wheel sinkage calculation. The method's applicability has been validated by experiments under various terrain conditions, which are flat terrain, raised terrain, hollow terrain, and rough terrain. Accuracy tests are done with the flat terrain, the results of the experiments indicate that the relative errors of the sinkage depth are around 10% and the relative errors of terrain interface angles are around 5%, when the actual sinkage depth is above 5mm.
China’s first Mars rover, Zhurong, has successfully touched down on the southern Utopia Planitia of Mars at 109.925° E, 25.066° N, and since performed cooperative multiscale investigations with the Tianwen-1 orbiter. Here we present primary localization and surface characterization results based on complementary data of the first 60 sols. The Zhurong rover has traversed 450.9 m southwards over a flat surface with mild wheel slippage (less than 0.2 in slip ratio). The encountered crescent-shaped sand dune indicates a NE-SW local wind direction, consistent with larger-range remote-sensing observations. Soil parameter analysis based on terramechanics indicates that the topsoil has high bearing strength and cohesion, and its equivalent stiffness and internal friction angle are ~1390-5872 kPa∙m-n and ~21°-34° respectively. Rocks observed strewn with dense pits, or showing layered and flaky structures, are presumed to be involved in physical weathering like severe wind erosion and potential chemical weathering processes. These preliminary observations suggest great potential of in-situ investigations by the scientific payload suite of the Zhurong rover in obtaining new clues of the region’s aeolian and aqueous history. Cooperative investigations using the related payloads on both the rover and the obiter could peek into the habitability evolution of the northern lowlands on Mars.
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