The role of spine elasticity on legged locomotion

Robot locomotion has become increasingly common in transporting and assisting humans in complex environments. However, most existing quadrupedal robots have been developed with only a single rigid trunk and limited actuation to the legs and associated joints to reduce design and controls complexity. This paper presents a non-linear optimization process to identify the highest performance gait parameters of a quadruped robot with a flexible trunk. The optimization process is conducted using evolutionary algorithms, which are based on a heuristic search inspired by Charles Darwin's theory of natural evolution and reflect the process of natural selection. Since identifying optimal gaits requires the complete definition of ground reaction forces coupled with the optimal trajectories of the body and its vibrational modes, it is possible to determine the influence of the main parameters linked to the vibration of the trunk on the optimal gait resulting from the optimization process. The paper's final part presents a comparison between results obtained in the case of a flexible spine and the case of a rigid trunk to demonstrate the benefits of the elastic model in terms of efficiency.