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Keisuke Takehana, Kenta Sawa, Kentaro Uno, Shreya Santra, and Kazuya Yoshida
This study focuses on the locomotion characteristics of a high-speed lunar exploration rover. On the loose soil such as lunar regolith, wheeled mobility systems often encounter wheel sinkage and slippage, leading to trafficability challenges. While conventional exploration rovers are designed to improve mobility using grouser wheels, their exploration speed remains relatively slow (~10^-2 m/s). High-speed traversal is essential for expanding exploration areas in future missions. In this paper, we conduct single-wheel tests under high-speed conditions and provide detailed results from force measurements. Three types of wheels are prepared: no grouser, low grouser, and high grouser, and their traction performance are compared. The testbed allows speeds of 1 m/s, which is about a hundred times faster than conventional exploration speeds. We measured traction coefficients (the ratio of drawbar pull to vertical load) and traction efficiency (the ratio of input energy to output energy) for variable slip ratios to assess traction performance. Our results revealed a trend where traction performance decreases as driving velocity increases. This behavior of performance at various speeds differs from that at low speeds. Each performance exhibited substantial dependence on the slip ratio, with efficiency peaking around a slip ratio of approximately 5% to 10%. Additionally, experiments varying grouser height under identical driving conditions demonstrated improved traction performance with higher grouser wheels. Through this experimental evaluation, we confirmed the effectiveness of grouser wheels even at high speeds. These terramechanical findings contribute to the wheel design and locomotion control of next-generation exploration rovers.
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