H_∞ Filtering And Its Application To The Wave Disturbance

In the ship motion control, the heading angle of ship is affected badly by the wave disturbance. If the wave filter is applied, the high frequency effect of the wave disturbance can be reduced greatly and the control performance can be improved. At the present, Kalman wave filter, the time-variant wave filter and the first-order wave filter are familiar. They can filter the wave disturbance, but they have faultiness in some aspect, so H filtering technology is introduced. Compared with Kalman filtering, the unknown definite disturbance with finite energy instead of white noise drives the state-space system in H filtering. Compared with the time-variant filter and the first-order filter, H filter has preferable robustness. H filtering technology and its application to the design of wave filter for ships are systemically investigated in this thesis. H wave filter with better robustness is designed and simulated by Simulink. Main content of the thesis are as follows.1. For the better comprehension of H standard control equation and H filtering technology, some mathematic knowledge is introduced simply, such as signal norm, system norm, algebraic Riccati equation etc.2. Before H wave filter is designed, the control system model must be known, so the mathematics model of the ship motion and the wave disturbance are introduced.3. Based on the ship course control system, H wave filter using the linear wave model is designed and simulated through three aspects. Firstly, while the nominal model is used, the filtering effect is very good. Secondly, when the system model isn't definite, the filtered heading angle and rudder angle are steady in the error range. Finally, when the complicated nonlinear wave model replaces the linear wave model, the filtering effect is also steady, and the estimate precision is high. In a word, H wave filter that is designed in this thesis can filter availably the wave disturbance and has better robustness.