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

Abstract

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 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 salamander 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 body's and limbs' movements and the relative speed of locomotion.

Where are we in understanding salamander locomotion: biological and robotic perspectives on kinematics

“…Therefore, the narrow range of bending angles in salamanders may be a result of the trade-off between stride length and energy efficiency. It is worth noting that Crespi et al (2013) reported striking similarities in the performance and kinematics of Salamandra robotica II and real salamanders which is also evident in Figs. 9 and 10.…”

“…Lateral bending during forward walking Experiments with a kinematic model of Salamandra robotica II and the real robot showed that higher trunk bending yields greater stride length (Karakasiliotis and Ijspeert 2009;Crespi et al 2013. However, both the model and the robot showed that there is a maximum value of bending after which the stride length starts to decay (Fig.…”

“…From the short list of salamander-like robots, Salamandra robotica II (Crespi et al 2013;Karakasiliotis and Ijspeert 2009) is the only one that addressed questions related to kinematics. Its predecessor, Salamandra robotica I (Ijspeert et al 2007) was used mainly to demonstrate walking and swimming gaits generated by a model of the neuronal circuits which enable the transition between these two gaits.…”

“…Therefore, stance and swing periods can be set independently to alter the gait's pattern. During swimming, the limbs are folded backward (Crespi et al 2013) similarly to the ones of its biological counterpart. A significant difference between the existing salamander-like robots and real salamanders for which kinematic data are available, Fig.…”

“…Ijspeert et al (2007) used a central pattern generator implemented (CPG) as a system of coupled nonlinear oscillators. A simplified version of this CPG model was used later by Crespi et al (2013). Karakasiliotis and Ijspeert (2009) used a simple sinebased controller.…”