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Mai Shimizu and Shingo Ozaki
The development and operation of exploration rovers is important for human lunar exploration, which is considered an international space exploration goal. However, the lunar surface is a completely different environment from that on the Earth because it is under 1/6G and is covered with regolith. Hence, it is difficult to evaluate rover’s traveling performance in advance. Under these circumstances, the extended terramechanics (xTerramechanics) model has been proposed that takes terrain surface deformation into account. In this study, systematic single-wheel traveling analyses assuming a lunar surface are performed based on the xTerramechanics model. First, the effect of soil parameters assuming Toyoura sand and regolith simulant (FJS-1) is examined. Then, the similarity law of gravity is examined by setting gravity levels as 1G and 1/6G under three different soil conditions (dense Toyoura sand, dense FJS-1, and loose FJS-1). Furthermore, an analysis is also conducted under the condition in which the wheel load is adjusted to the lunar surface (1/6M under 1G), and the significance of the simulated environment experiments on the Earth was discussed. As a result, it is revealed that the similarity law of gravity may be valid only when a cohesion of soil is negligible. In addition, it is shown that when conducting experiments on the Earth ground, it is important to consistent the sinkage and wheel contact area to the 1/6G condition than to consistent the wheel load to the 1/6G condition.
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