Analysis of the Traveling Performance of Planetary Rovers with Wheels Equipped with Lugs over Loose Soil

The surfaces of the Moon and Mars are covered with loose soil. In such conditions, planetary rovers can get stuck and even cause failure of an exploration mission. To avoid such problems, the wheels of planetary rovers typically have lugs (i.e., grousers) on their surface, which substantially improve their traveling performance. However, there exists no theoretical method to determine a suitable lug interval. In this study, we first modeled the linear traveling speed of a wheel with lugs and provided guidelines for determining a suitable lug interval, as well as the corresponding terramechanical stress models. Next, to verify the suitable interval for lugs, we performed traveling tests using a two-wheeled rover with wheels having different numbers of lugs of different heights. According to the experimental results, when a wheel has three lugs in a range where normal stress is generated beneath it, it can travel with constant speed while the traveling performance is substantially improved.