Development of rover designed to climb steep slope of uncompacted loose sand

Unmanned rovers have proved their usability in various operations, often involving challenging terrain environments, for example the sand dunes of Mars for planetary rovers and ash with rubbles for volcanic observation. Most of the current rovers are equipped with wheels or tracks, which have a high tendency to get stuck when climbing steep slope made out of loose sand. We are developing a prototype rover leg-wheel that is mechanically simple, which is designed to climb steep slope of loose sand with the help of a variable center of gravity mechanism and an independently adjustable lower-leg angle. Preliminary experiments were done on natural uncompacted loose beach sand and the soft sand slope climbing performance of the mechanism using the first prototype is compared with a wheel with grousers. The effect of the position of the center of gravity on the climbing performance was also investigated. It was observed that the proposed leg-wheel mechanism generates less slippage when climbing 20 and 30 degree slopes of soft sand. The leg-wheel mechanism also requires less maximum output torque to climb the slopes. Shifting the center of gravity forward while moving upslope also increased the average travel distance of the rover. The flaws of the first prototype, which is the vertical bobbing during movement, exposed moving mechanical parts and short travel distance per revolution is addressed by designing a new prototype rover. To ensure a more consistent sand condition and allow more accurate modeling, a new indoor sand testbed was designed for a more thorough investigation.