Kinematic primitives for a quadruped robot walk and trot with compliant legs

• Main Authors: Alexander Thomas Sprowitz, Mostafa eajallooeian, Alexandre eTuleu, Auke Jan Ijspeert
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2014-03-01
• Series: Frontiers in Computational Neuroscience
• Subjects: central pattern generator; motion primitives; entrainment; Coupled oscillators; locomotion patterns; quadruped robot
• Online Access: http://journal.frontiersin.org/Journal/10.3389/fncom.2014.00027/full

In this work we research the role of body dynamics in the complexity of kinematic patterns in a quadruped robot with compliant legs. Two gait patterns, lateral sequence walk and trot, along with leg length control patterns of different complexity were implemented in a modular, feed-forward locomotion controller. The controller was tested on a small, quadruped robot with compliant, segmented leg design, and led to self-stable and self-stabilizing robot locomotion. In-air stepping and on-ground locomotion leg kinematics were recorded, and the number and shapes of motion primitives accounting for 95% of the variance of kinematic leg data were extracted. This revealed that kinematic patterns resulting from feed-forward control had a lower complexity (in-air stepping, 2 to 3 primitives) than kinematic patterns from on-ground locomotion (4 primitives), although both experiments applied identical motor patterns. The complexity of on-ground kinematic patterns had increased, through ground contact and mechanical entrainment. The complexity of observed kinematic on-ground data matches those reported from level-ground locomotion data of legged animals. Results indicate that a very low complexity of modular, rhythmic, feed-forward motor control is sufficient for level-ground locomotion in combination with passive compliant legged hardware.