Undulatory Swimming Locomotion Driven by CPG with Multimodal Local Sensory Feedback

Many species such as eels, lampreys and leeches generate undulatory swimming locomotion adaptively. It is said that this coordinated locomotive patterns are produced by central pattern generators (CPGs) which generate rhythmic activities without any rhythmic inputs. Additionally, there are some local sensors underlying in their bodies (e.g. lampreys: stretch receptors, larval zebra-fish: lateral organs). We assumed that such several sensors likely cooperate and influence their adaptive locomotion with CPGs. However, there is still very little understanding how CPGs and multimodal local sensors interact for adaptive locomotive patterns. In this study, we aim to design a minimal CPG model for a swimming robot with multimodal local sensory feedback which can produce an adaptive undulatory swimming locomotion. Finally, we validated it under different conditions via 2D simulation.

Central pattern generators for locomotion control in animals and robots: a review

Auke Ijspeert

The problem of controlling locomotion is an area in which neuroscience and robotics can fruitfully interact. In this article, I will review research carried out on locomotor central pattern generators (CPGs), i.e. neural circuits capable of producing coordinated patterns of high-dimensional rhythmic output signals while receiving only simple, lowdimensional, input signals. The review will first cover neurobiological observations concerning locomotor CPGs and their numerical modelling, with a special focus on vertebrates. It will then cover how CPG models implemented as neural networks or systems of coupled oscillators can be used in robotics for controlling the locomotion of articulated robots. The review also presents how robots can be used as scientific tools to obtain a better understanding of the functioning of biological CPGs. Finally, various methods for designing CPGs to control specific modes of locomotion will be briefly reviewed. In this process, I will discuss different types of CPG models, the pros and cons of using CPGs with robots, and the pros and cons of using robots as scientific tools. Open research topics both in biology and in robotics will also be discussed.

2008

Roombots: Design and Implementation of a Modular Robot for Reconfiguration and Locomotion

Alexander Spröwitz

In this thesis we present the design and implementation of a novel self-reconfiguring modular (SR-MR) robotic system: Roombots. We are aiming at three main applications with Roombots; locomotion through self-reconfiguration in the regular cubic 3D-lattice on structured surfaces, locomotion in non-structured environments applying central pattern generators (CPG) as the locomotion controller, and self-assembly and reconfiguration of static objects of the day-to-day environment, such as furniture. Robot assemblies from self-reconfigurable modular robots have the ability to adapt to a given task and working environment by altering their shape through a series of reconfiguration moves, and attachments and detachments between the modules. We are interested in self-reconfiguring modular robots for their shape-changing capabilities, and their distributed characteristics. We envision the following applications for Roombots: First, self-reconfiguration in a structured 3D lattice, i.e. a floor and walls equipped with connectors. Embedded connectors can provide pivot points for locomotion of SR-MR assemblies, and docking and recharging places for our adaptive furniture pieces. Second, our proposed concept for locomotion control of modular robots on non-structured ground are central pattern generators. Third, we would like to build adaptive and versatile furniture from modular robots and light-weight elements. In the following we are able to count more than 60 modular robotic systems, developed over the last two decades. However we were unable to identify an existing system which could provide us with all desired kinematic and geometric capabilities. This led us to design and implement a novel self-reconfiguring modular robotic system: Roombots. To tackle the module design we attempt to identify both meaningful design parameters from existing modular robots, and essential features for our applications. The combination of both leads to the kinematic and geometric description of the Roombots modules, and eventually to its implementation. In order to be able to assemble furniture from our Roombots units in the future, we need a reconfiguration framework which supports the specific requirements of Roombots. Metamodules made of two units attached in-series are attracted and guided by a virtual force-field, they use broadcast signals, look-up tables of collision clouds and simple assumptions about their near environment to reach their seeding positions, which are currently hand coded. For the task of locomotion in non-structured environments we propose a framework for learning to move with modular robots using central pattern generators and online optimization. The distributed implementation of CPGs offers an ideal substrate for producing locomotion patterns and for online learning, and an optimization framework for fast learning.

EPFL2010

Legged locomotion with spinal undulations

Konstantinos Karakasiliotis

Legged locomotion with spinal undulations is a topic that has not received much attention yet in robotics, though, vertebrates depend on both their limbs and spine to move efficiently in their environments. In this thesis, my aim is to get more insights into the role and function of these two body parts as well as their coordination. Biology provides several answers to these questions. Salamanders and lizards are great biological paradigms for studying animal locomotion with limbs and flexible spine. Not only do they have a highly flexible spine and limbs that can sometimes vary in strength or even number, but they also demonstrate a rich repertoire of locomotor modes. They can walk on land, while they can swim and walk in water. This provides many more examples on the ways that limbs and spine function and coordinate. Biorobotics is a growing field of robotics that aims at answering questions that cannot be answered from animal observations. Those questions often deal with the development of a specific function of a body part. In my studies, I initially used a bio-inspired amphibious salamander-like robot Salamandra robotica II to extract basic principles of salamander locomotion. Although the improvements of the limb and tail designs enhanced the robot’s performance to a level that was surprisingly close to the salamander’s, several limitations were identified owing to the simplicity of the bio-inspired design. These limitations motivated me to design a new amphibious salamander-like robot, Pleurobot, which is capable of replicating the movements of salamanders with reasonable accuracy. A novel methodology was also used during this process which proved to be effective but simple at the same time. Three-dimensional kinematics of the salamander’s skeleton were recorded and used to guide the design process and optimization of the robot’s morphology and joints’ topology. The raw angular kinematics, extracted from X-ray biplanar videos of salamanders, were then used to drive the joints of Pleurobot, resulting in natural-looking and effective locomotion. The main contributions of this thesis are two-fold: i) biological data and robotic prototypes that improve our understanding on sprawling locomotion and ii) a successful methodology for robotic design for more animal-like robots and agile control