A nonlinear estimate filter designed for ship dynamic positioning

A nonlinear estimate filter was designed for a dynamic positioning system. The global exponential stability of estimate filter was proven using Lyapunov methods. The main advantage of the nonlinear design to Kalman filter is that the kinematics equations of motion need not be linearized. The proposed estimate filter includes an estimation of both the low-frequency position and velocity of the ship from noisy position measurements, environmental disturbance and wave filtering. The simulation results show the excellent performance of the nonlinear estimate filter.