Tuning parameters sensitivity analysis study for a DP roll–pitch motion controller for small waterplane surface vessels

Abstract

For surface vessels with small waterplane area and low metacentric height, which results in relatively low hydrostatic restoring force compared to inertial forces, an unintentional coupling between the vertical and horizontal plane motions can be invoked through the thruster action. A novel controller dedicated to mitigating the unintentional roll and pitch motions of a dynamically positioned vessel has been proposed by the authors. As a continual study of that, this paper conducts a sensitivity analysis of the controller tuning parameters. A possible criterion comprised of several key variables representing different perspectives of the controller performance is proposed, followed by a guide for optimization their weighting factors by non-dominated sorting genetic algorithms algorithm. The sensitivity analysis was performed by a time domain simulation of a dynamically positioned semi-submersible platform. The simulation results reveal that the controller performance is crucially affected by the advance coefficient, that determines how large the ratio of the roll and pitch angles to their limiting angles that activates the proportional roll–pitch controller. The proposed parameter sensitivity analysis methodology can be used as a tool to determine appropriate roll–pitch controller gains with high positioning performance.