Motion Model And Control Methods Of Under Water Vehicle Hovering System

Recently, with the development of deep submergence technique, underwater vehicle (UV) has been widely used in deep sea activities, such as integrated research, resource survey, etc. It has gotten more and more attention. The motion control system of a dynamic positioning system is a nonlinear, coupling system. It's difficult to control the system effectively using the conventional control method. For this reason, higher requirements of manoeuvring for UV are brought forward. In some special applications, such as lifesaving and oceanographic mapping, we need to keep the depth and pitch of UV at zero advancing speed, and the conventional steering control system has no effect.The simulation models of hovering system are established based on it's peculiarities. The models are derived from four degrees of freedom movement model in dive plane of submarine. All kinds of interference force model of hovering system are analyzed. Simulation of wave disturbances for near-surface hovering is based on the shape of the hull. Making reasonable simplification of system model and turning into the affine nonlinear system of state-space form based on the high-order and nonlinear of hovering system. Decoupling the complex nonlinear system into two comparatively simply linear systems: depth control system and pitch control system by using input-state linearation approach of differential geometric control theory. Designing the controllers for these comparatively linear systems by using pole assignment method. The simulation results of hovering depth and pitch under wave disturbances show that these nonlinear decoupling methods are effective.Hovering depth and hovering pitch are fluctuant with near-surface wave disturbance. We need to restrain the influence of wave disturbance effectively. For this reason, this paper construct the inverse system of the equivalent compound system. Then using the inverse model to construct the model-reference inverse system to suppress the interference of wave force. The simulation shows that hovering depth and hovering pitch can be maintained accurately at the desired value by this method, at the same time, the dynamic performance of original system isn't infected.