Passive nonlinear observer design for special structure vessels

In most ship motion control problems, the output measurements contain high frequency data and noise measurements. This article presents a passive nonlinear observer design for special structure vessels, and the observer can filter the noise and high frequency data. For dynamic positioning vessels, the Coriolis-centripetal matrix (C-matrix) in the model is ignored and the inertia matrix is symmetric. These properties simplify the process of designing state observer. However, to reduce the observe error and improve the control effect, the C-matrix cannot be ignored. But the existence of C-matrix brings difficulty to the observer design. Acceleration feedback (AFB) technology and coordinate transformation are introduced to overcome this problem. Utilizing the AFB, the system inertia matrix can be reshaped to a symmetric one. Then the C-matrix can be removed through coordinate transformation.