Equilibrium Points Behavior for Marine Propulsion Control Techniques

Abstract

This paper presents an equilibrium point analysis of three propulsion control techniques, namely shaft speed, torque and power controllers applied to a modeled ducted marine propeller driven by an electrical motor. The control loop scheme follows the structure of propulsion control in a Dynamic Positioning system. The sensitivity concept is used to perform the analysis, which consists of a normalization of the equilibrium point with respect to its reference value. The effect of inaccuracies between the control model and plant parameters over the equilibrium points is considered and analyzed in three scenarios for each controller. The equilibrium points of a ducted propeller model are calculated for the whole range of operation and the results are compared by using performance measurements based on the Mean Absolute Error. Thereby, this work provides detailed information on the characteristics of each controller in steady state regarding shaft speed, torque, power and thrust, depicting pros and cons in different situations.