Automatic alignment of underwater snake robots operating in wakes of bluff bodies

This paper presents the development of controllers to automatically align an underwater snake robot (USR) with a wake that forms behind a bluff body, while swimming at a desired distance to the object. The low-level controllers stabilize the joint motion of the USR to a swimming gait while achieving a desired orientation and tangential velocity. The high-level controllers are designed to select references for the orientation and tangential velocity to achieve a desired placement and alignment. The control system is analyzed and proven uniformly practically asymptotically stable (UPAS). The proposed control method is validated through high-fidelity simulations that capture the intricate interaction between the USR and the surrounding fluid, and is seen to perform well in these simulations.