Effects of wheel width on running performance of four-wheeled small lunar rover

As future lunar habitation plans progress, the importance of landing-based exploration is increasing. Small lunar rovers are considered effective for such missions due to their low deployment risk and cost. However, these rovers are prone to slippage and immobilization on soft terrain formed by lunar regolith, which can interfere with mission operations. Wheeled locomotion systems are widely adopted for their structural simplicity and stability; however, they tend to experience significant sinkage and slippage on steep slopes, often resulting in immobilization. This study focuses on wheel width, a key parameter directly related to ground pressure and contact area, which significantly affects mobility performance. A small lunar rover and seven types of wheels with different widths were fabricated. Running tests were conducted on two types of terrain: FJS-1 lunar regolith simulant, which offers high fidelity based on sample return data, and silica sand, commonly used in terrestrial testbeds. By comparing the results across these terrains, the effect of wheel width on rover mobility was evaluated. On silica sand, wider wheels improved mobility, while on the simulant, narrower wheels performed better. These findings reveal that the optimal wheel width differs depending on the soil type, and suggest that wheel width optimization is essential for the design of locomotion systems for future lunar exploration rovers.