A novel alternating glide–drift operation mode for energy-efficient underwater glider missions

Underwater gliders (UGs) enable long-duration ocean observation with low energy consumption, yet conventional operation strategies often neglect the potential benefits of passive surface drifting. This paper proposes an alternating glide–drift operation mode to improve energy efficiency during long-range missions. An integrated model is developed to characterize motion dynamics, mode transitions, and energy consumption under three-dimensional ocean currents. Based on this model, an energy-efficient operation framework is established to adaptively regulate surface-drifting duration according to local current conditions. Simulations using Copernicus Marine current data demonstrate that the proposed strategy effectively exploits favorable surface currents to reduce energy consumption. Compared with a fixed minimum-drifting-time strategy, the proposed approach reduces total energy consumption by decreasing the number of underwater-gliding cycles, albeit at the cost of increased mission duration. These findings demonstrate the potential of coordinated gliding and passive drifting to enhance ocean-current utilization and extend UG endurance.