Stability analysis of yaw motion for sandglass-type floating body with dynamic positioning system under regular excitation

For the new sandglass-type floating body with special shape, this paper mainly analyzes its yaw stability under dynamic positioning system. Firstly, by considering the construction tolerance within the range of engineering accuracy, surge and yaw coupled motion equations of the sandglass-type FPSO based on dynamic positioning system are established. Secondly, the yaw instability phenomena of sandglass-type model can be found by Runge-Kutta numerical method. On this basis, a nonlinear yaw motion equation of parametric excitation can be reasonably deduced. Then the multi-scale method and LP (Lindstedt-Poincaré) method are used to study the stability characteristic of yaw motion for sandglass-type floating body. Finally, the effects of initial heading angle and control parameters on the yawing stability of the sandglass-type floating body are discussed. •The yaw instability of the sandglass-type FPSO with DPS under the allowable construction tolerances was found.•The nonlinear yaw motion equation with parametric excitation was deduced to analyze the essence of yaw instability.•The multi-scale method is convenient and accuracy to describe the zero-solution boundary of yaw stability.