Compliant terrain legged locomotion using a viscoplastic approach

Abstract

Legged locomotion is a rapidly advancing area in robotics, yet still a large number of open questions exist. This work focuses on the foot-terrain interaction and its effect on the motion of a one-legged system. This interaction is usually tackled by disregarding some of the effects of ground deformation like permanent deformation and compaction. Inspired by other areas of engineering, an impact dynamics model is developed, allowing a more thorough study of the behavior during fast dynamic walking. This approach can be regarded as a viscoplastic one. The monopod controller presented in previous work is extended to cope with deformable terrains, based on energy dissipation considerations, without requiring the knowledge of the ground parameters. Simulation results prove the validity of the theory presented.978-1-4799-6934-0/14/$31.00 ©2014 IEEE 4849

Quadruped pronking on compliant terrains using a reaction wheel

“…In [4], a novel controller for a monopod hopping robot on compliant terrains, called Extended Multipart (x-MP), was presented. The controller is capable of achieving and retaining a desired forward speed and main body apex height on different terrains, with a single actuator located at the robot hip.…”

“…To describe realistically the leg interaction with the deformable ground during its motion, the viscoplastic impact model proposed in [4] is employed. According to this model, the interaction force F g at stance instance i is,…”

“…The index i is used to identify an impact instance (stance), as the terrain inherits the characteristics from the previous impact instant. The coefficient recursive form and proposed model is presented in [4]. Finally, the depth y e i at the i th impact can be calculated using the maximum compression, y c,max i , as follows,…”

“…The terrain is considered stiff and completely even. The effects of compliant terrains were taken into account in our recent work in which we developed a novel energy-based controller for a monopod hopping robot running over compliant terrains, using only one actuator [4].…”

“…For example, a viscoelastic model was used in [5], while a terradynamics approach was employed in [6]. A viscoplastic model has been proposed, which enables the assessment of the effects of terrain permanent deformations by taking into account various realistic parameters such as compaction in fast dynamic walking [4].…”