Buoyancy and Propulsion Mechanisms for Stable Movement in Snow Field

For small-sized mobile machines, moving on snow without sinking is challenging. Snowmobiles are often used to move on snow. However, in smaller-sized machines, the skis attached to the machine become small, so small snow bumps or soft powdered snow quickly cause the entire machine to be buried under the snow. Therefore, it is necessary for small robots moving on snow to give appropriate driving mechanisms for producing propulsive force and snow-floating force. To this end, we propose new driving mechanisms, a “passive wing wheel” and a “spiral screw,” for small mobility services that move on snow without sinking or getting stuck. The passive wing wheel has transformable wing-like paddles, which extend to behave like animal feet and shrink to form a wheel if necessary. The spiral screw is designed to produce propulsive force by pushing snow particles with the screw. Additionally, by combining two sets of screws having opposite threads, they gather snow underneath the body attached to them, which causes floating force. This report also proposes ways to prepare pseudo-snow, which resembles natural snow in hardness, viscosity, and property transformation due to deformation. We conducted experiments to measure the performance of the proposed design in both the pseudo-snow and natural snow. From experiments, we confirmed that the mechanism performs well in terms of propulsion and floating on snow.