Legged locomotion with spinal undulations

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