Salamandra Robotica II: An Amphibious Robot to Study Salamander-Like Swimming and Walking Gaits

TLDR

The study builds on the earlier Salamandra robotica I, presenting an improved amphibious robot design. The authors aim to present Salamandra robotica II, an amphibious robot capable of walking and swimming, and to investigate body‑limb coordination in sprawling posture animals. Salamandra robotica II features four legs and an actuated spine that enable anguilliform swimming and ground walking, and the study examines how locomotion speed and turning curvature depend on gait parameters such as body‑limb coordination, undulation type, amplitude, phase lag, and frequency. Comparisons with real salamanders reveal striking similarities in the timing of body and limb movements and in locomotion speed.

Abstract

In this paper, we present Salamandra robotica II: an amphibious salamander robot that is able to walk and swim. The robot has four legs and an actuated spine that allow it to perform anguilliform swimming in water and walking on the ground. The paper first presents the new robot hardware design, which is an improved version of Salamandra robotica I. We then address several questions related to body-limb coordination in robots and animals that have a sprawling posture like salamanders and lizards, as opposed to the erect posture of mammals (e.g., in cats and dogs). In particular, we investigate how the speed of locomotion and curvature of turning motions depend on various gait parameters such as the body-limb coordination, the type of body undulation (offset, amplitude, and phase lag of body oscillations), and the frequency. Comparisons with animal data are presented, and our results show striking similarities with the gaits observed with real salamanders, in particular concerning the timing of the body's and limbs' movements and the relative speed of locomotion.