Motion Characteristics Analysis of the Wave Glider Under Wave and Current Coupling

The wave glider is an unmanned marine observation platform propelled by wave energy. Accurate prediction of its motion performance is crucial for structural design and motion control. This paper presents a four-degree-of-freedom nonlinear coupled dynamic model for wave gliders in complex marine environments, developed using a separated-body modeling approach. The model incorporates the torsional properties of the umbilical cable and includes coupled environmental forces that account for wave–current interactions. Simulation results demonstrate that the proposed model agrees well with existing studies. Based on the model, experimental analyses were conducted to investigate the turning and heading tracking performance under various operational conditions. The findings reveal that the rudder angle determines the radius and direction. The significant wave height influences the longitudinal velocity and turning rate; the average longitudinal velocity increases from $0.15\mathrm{m}/\mathrm{s}$ (at $0.5\mathrm{m}$ wave height) to $0.3\mathrm{m}/\mathrm{s}$ (at $1.25\mathrm{m}$ wave height), leading to a notable increase in turning cycles per unit time. Current disturbances cause trajectory drift, the pattern of which depends on the wave–current angle, exhibiting a distinct $\eta$-direction offset under ${90}^{\circ }$ conditions. A conventional PID controller fails to achieve precise heading maintenance under second-order wave forces. The surface float exhibits more pronounced oscillations than the submerged glider, and the heading deviation becomes more severe at a wave height of $1.25\mathrm{m}$.