Coupled Directional Stability of Multiple Ship Formations

This thesis addresses the problem of coordinated motion control and the stability loss of surface marine vehicles. The mathematical model is based on Nomoto s second order model which captures the fundamental dynamics of turning on the horizontal plane with no side slip. A state feedback control law is coupled with a line of sight guidance law to provide path control. A string of three vehicles is considered where each vehicle is using the vehicle in the front as a reference point. The coupled motion stability of the formation is analyzed by linearization. It is shown that under the assumed dynamics, guidance, and control laws, the stability properties of the system decoupled into individual vehicles. This makes it possible to obtain exact analytical results that can be used in design. Parametric runs and sensitivity analysis studies show the effect of main vehicle geometric parameters on formation control and motion stability.