Quantitative evaluation of motion performances of underwater gliders considering ocean currents

Underwater gliders (UGs) have attracted great attention for their low cost, long range, high endurance, and broad applications in oceanography. However, few studies have been conducted to research motion performances of UGs. In this study, to understand the effects of ocean currents on the motion performances of UGs, a dynamic model of UGs considering ocean currents was established. Based on the dynamic model, motion simulations of the Petrel-II UG were conducted. The response time taken for the UG to return to the pitch angle of the undisturbed state, the relative rotation radius of steady spiral motion, and the UG's voyage in a single profile were used to quantitatively evaluate the stability of pitching motion, maneuverability, and cruising ability, respectively. The results show that UGs are self-stable in pitch degree after the disturbance disappears, and a positive axial ocean current or a negative vertical ocean current could remarkably improve UGs' cruising ability. This work provides a quantitative evaluation criterion for motion performances of UGs, enriching the comparative theory of UGs. The dynamic model considering ocean currents would also be useful in path planning and optimization of the control strategy of UGs, and it provides valuable guidance for engineering applications.