Steady-state spiral motion simulation and turning speed analysis of an underwater glider

Spiral motion is a typical motion of underwater gliders, which is usually used to change the direction of motion. Compared with the sawtooth motion in the vertical plane, the mechanism of spiral motion is more complex and less understood. In order to characterize steady-state spiral motion of underwater gliders, the dynamic model for underwater gliders, steered by a single internal movable and rotatable mass, is established. Through the comparison with published result of the Seawing glider, the dynamic model in this paper is validated. According to the direction of the vertical movement, the spiral motion is further classified as the upward spiral motion and the downward spiral motion, and the relationship between the turning speed and control inputs is established, which would provide guidance for the turning control of underwater gliders.