Komi, S.

Improvement of Cheetah-Cub locomotion by a new foot design

In this report, we explain the development and the test done on a new foot design for the quadruped robot CheetahCub, developed at Biorobotics Lab, EPFL. This design, based on simple mechanical features extracted of a biological model, is assessed in term of speed and stability. It is built by SLS 3D printer and shows flexible beam instead of standard rotational joint, in order to improve its energetic properties in term of conservation. The most important parameters of this new design are its independently articulated toes, the added tarsal-metatarsal joint and a compliant heel, that hypothetically have important impacts on the locomotion of the robot. The CPG driven robot allow us to test several gait and to perform a grid search for good locomotion parameters, achieving, at the end, a top speed of 0.72 m/s. The importance of some locomotion parameters, especially the hind hip offset are demonstrated and their impact quantified. The predicted benefits that the toes might have on the stability are rejected since the robot shows higher RMS pitch and roll value during walking gaits than it does using the old version of the feet. Interesting results concerning the joint stiffness are shown. The variability of the stiffness against the speed are explained and some design principles are proposed at the end of the report exploiting this specific parameter.