Kinematic primitives for walking and trotting gaits of a quadruped robot with compliant legs

Abstract

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, 2–3 primitives) than kinematic patterns from on-ground locomotion (νm4 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.

Editorial: Modularity in motor control: from muscle synergies to cognitive action representation

“…By using a soft robotic arm inspired by the octopus they show in a number of experiments how control is partially incorporated into the physical arm's dynamics and how the arm's dynamics can be exploited to approximate non-linear dynamical systems. Spröwitz et al ( 2014 ) implement kinematic primitives for walking and trotting gaits of a quadruped robot and show 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.…”

Realizing Learned Quadruped Locomotion Behaviors through Kinematic Motion Primitives

“…It must be noted that kMPs yield trajectories that are as good as the time averaged trajectories of the original data (which is eight dimensional). In addition, with kMPs, there is existing literature for obtaining derived behaviors like walk, trot and gallop [15], [38], which will be explained more in the next section.…”

Design, Development and Experimental Realization of A Quadrupedal Research Platform: Stoch

“…Smooth transitions from one type of gait to another. This is mainly motivated by the various locomotion behaviors realized by [5], [2] in their custom hardware. These various behaviors are then composed together and tele-operated by a remote control device.…”