A generalized propulsion control logic

Precise dynamic positioning requirements for drilling and other offshore applications necessitate precise coordinated thruster control. This paper describes the design implementation advantages and test results of a Generalized Propulsion Control Logic (PCL) System that was developed to generate thruster force and angle orientation commands for dynamically positioning a surface vessel. The PCL allocates thruster output level and azimuth angle commands to an arbitrary combination of fixed-axis thrusters, main screws, and steerable thrusters. The thruster allocation is composed of a fixed pointing angle, minimum energy allocation for all thrusters blended with an allocation that commands both thrust level and azimuth angle to all steerable thrusters. The combination of both allocations, blended according to the thruster power consumption, significantly reduces azimuth modulation of the steerable thrusters.