Development of a multibody model for the study of the dynamics of the locomotion of a hexapod robot

Abstract

The development of autonomous mobile robots has been growing motivated by their ability to perform duties without human supervision. Amongst these systems, hexapods take advantage of their locomotion stability to adapt the gait patterns to different terrain topologies, which increases the interest of their utilization for tasks involving unknown and complex scenarios. Moreover, their development must take into consideration the dynamics loads inherent to their locomotion in these conditions. Nonetheless, commercially available software only provides an estimation of the system-environment interactions, which may not provide good approximations for bodies behavior during both collisions with external objects and contact with the ground. Thereby, this work aims at building a detailed multibody model of the hexapod ATHENA (All-Terrain Hexapod for Environment Navigation Adaptability) and study its dynamic behavior using Newton-Euler formulation. This study requires the development of an in-house software based on python, which solves at each timestep a system of linear equations that describe the hexapod dynamic behavior. All the robot joints are treated as kinematic constraints and the robot-ground contact is modeled using an elastic approach. In this sense, suitable normal and tangential contact force models are applied to realistically describe those interactions. This work will allow that the developed multibody dynamic model of the ATHENA to be used to control the physical prototype in real time when travelling in a flat surface, based on the deviations in the angular positions of the joints during the robot-ground interactions. Other terrain topologies will be further studied in the future.