Interplay of theory and experiment in analysis of the advantage of the novel semi-elliptical leg moving on loose soil

A new method to reveal the effect on the novel semi-elliptical leg moving on loose soil was developed. The method combined an infinitesimal thought based model and bar drag experiment. In the theory model, the effect on the leg was obtained by integrating the effect on each element under the ground, which was mimicked by the bar drag experiment performed under the condition of different angles between its longitudinal direction and its own speed direction, different depths, as well as different speeds. The result predicted by our method corresponded well with the experimental result under the same condition. It was found that the force and torque have little relationship with the angular velocity of the leg in the range we considered. Different types of legs described by elliptical equation were also analyzed to reveal leg shape´s influence on robot´s performance. Analysis based on the study revealed the internal reasons for the novel leg´s advancement in loose soil overcoming, in addition, some general design principle and control strategy were also discussed to utilize the characters of the force and torque.