Behaviour diversity in a walking and climbing centipede-like virtual creature

TL;DR

This paper designs a single decentralised controller applicable to diverse morphologies and environments, and finds that six different modes of locomotion emerge from this controller in response to environmental and morphological changes.

Abstract

Robot controllers are often optimised for a single robot in a single environment. This approach proves brittle, as such a controller will often fail to produce sensible behavior for a new morphology or environment. In comparison, animal gaits are robust and versatile. By observing animals, and attempting to extract general principles of locomotion from their movement, we aim to design a single decentralised controller applicable to diverse morphologies and environments. The controller implements the three components 1) undulation, 2) peristalsis, and 3) leg motion, which we believe are the essential elements in most animal gaits. The controller is tested on a variety of simulated centipede-like robots. The centipede is chosen as inspiration because it moves using both body contractions and legged locomotion. For a controller to work in qualitatively different settings, it must also be able to exhibit qualitatively different behaviors. We find that six different modes of locomotion emerge from our controller in response to environmental and morphological changes. We also find that different parts of the centipede model can exhibit different modes of locomotion, simultaneously, based on local morphological features. This controller can potentially aid in the design or evolution of robots, by quickly testing the potential of a morphology, or be used to get insights about underlying locomotion principles in the centipede.

Figures (11)

• Figure 1: Illustration of the experiment setup. The controller adapts to the environment and morphology of the centipede model based on proprioceptive feedback, creating a variety of gait patterns. The controller requires no training or retuning upon encountering a new environment or morphology.
• Figure 2: The centipede model in a) top view, b) front view, and c) side view. The solid black lines are passive spring-damper connections, the pink dashed lines are linear actuators, and the orange dotted lines are rotational actuators. The axes denote the (Y) yaw, (P) pitch, and (R) roll axes of the model.
• Figure 3: The centipede model is first tested while walking on a flat plane (left), then while climbing up a pole (right).
• Figure 4: The relationship between the leg phase and the position of the leg (left), and between the leg phase and the position of the foot (right). The arrow shows the direction that the leg or foot is heading. Note that the left diagram shows the model in top view, while the right diagram shows it in front view.
• Figure 5: The six patterns we detect to categorize the gaits, 1) in-phase gait, 2) peristaltic gait, 3) low undulation direct gait, 4) high undulation direct gait, 5) low undulation retrograde gait, and 6) high undulation retrograde gait. The retrograde gaits produce a visual pattern where it looks like clusters of legs are moving downwards towards the tail. The direct wave gaits produce the opposite effect where it looks like the clusters are moving upwards towards the head. This is denoted by the arrows. The in-phase and peristaltic gaits (1 and 2) usually exhibit a retrograde wave.