The simulation of the ROV motion with anti-pitch control in uniform current

In the paper, a hydrodynamic numerical model for predicting the ROV motion with anti-pitch control is presented. The six degrees of freedom of equations of motions are formulated, which includes the coupled effect due to the current and the umbilical cable. Because of the umbilical cable on the ROV, the two-point boundary value problem with respect to a set of first order ordinary differential equation system arises and a multi-step shooting method is suggested to solve this problem. The anti-pitch technique including the depth keeping, either by PD control or PID control, is proposed to maintain the attitude of ROV in the current to reduce the resistance and other disturbance. The results reveal that both controlled techniques can indeed reduce the pitch motion and keep the desired depth for the ROV even in strong current. The hydrodynamic model developed here can therefore serve as a useful tool to improve the performance of the ROV operated in uniform current.