An Experimental Investigation of Path Following for an Underwater Snake Robot with a Caudal Fin

In this paper, we present a bioinspired underwater snake robot (USR) equipped with a passive caudal (tail) fin. In particular, a highly flexible configuration of a USR is presented, which is capable of locomotion both on ground and underwater due to the robust mechanical and modular designs where additional effectors can be attached at different modules of the robot depending on the requirements of the application. This gives flexibility to the operator, who can thus choose the proper configuration depending on the task to be performed in various uncertain environments on ground and underwater. Experimental results for straight line path following control are obtained for a physical USR, that enable a comparison of the USR motion with and without the passive caudal fin, both for lateral undulation and eel-like motion patterns. The experimental results show that a path following control approach which has previously been proposed for USRs without tail fin, can be directly applied to solve the path following control problem of this bioinspired USR with a passive caudal fin. In particular, it is shown that the path following control approach successfully steers the robot towards and along the desired path, and furthermore the results show that it is possible to almost double the forward velocity of the robot by using a passive caudal fin.