Tuning control parameters of underwater vehicle to minimize the influence of internal solitary waves

ISWs (Internal solitary waves) are waves that occur in stratified oceans, generating strong shear near the pycnocline. Encountering ISWs can cause a vehicle to experience the phenomenon of “falling deep”. Therefore, it is quite necessary to exert control on the vehicle in order to effectively avoid this phenomenon. This study establishes a numerical wave tank for ISWs based on the mKdV (modified Korteweg de Vries) theory. Additionally, a PD (Proportional Derivative) control method is developed for vehicles encountering ISWs in stratified fluids. The PD control parameters are designed and tuned, and the vehicle's control effectiveness, motion response and hydrodynamic characteristics, are analysed. The results suggest that this control method can effectively reduce the heave and pitch motions of the vehicle in different submergence depths and wave amplitudes. The pitch angle can be controlled within 0.2 rad for different control parameters. Better control can suppress changes within a range of 0.1 rad. To better evaluate the control effect, a new evaluation parameter σ is proposed, which takes into account both heave and pitch motions. After implementing control, the value of σ max significantly decreases. Optimal control parameters can reduce the value of σ max by about 90% compared to an uncontrolled vehicle.