Rudder Roll Stabilization Systems


Rudder Roll Stabilization (RRS) is a technique which uses the vessel's rudders to simultaneously steer and counter roll. This eliminates expensive and vulnerable roll fins and cross axis coupling in which the roll fins degrade steering accuracy and separate steering control induces roll. This requires a very fast rudder movement and robust steering gear due to the high duty cycle.  These features are inherent in Autonav rotary vane and pumpset designs.


Autonav RRS was developed in cooperation with the Canadian National Research Council.


Use rudders to control heading and reduce roll

•Low frequency motions control heading

•High frequency motions reduce roll

•Largely independent of each other under optimal control

•Control systems minimize cross-axis coupling between steering and roll (especially evident when steering and roll fins are designed separately)


Take advantage of Non-Minimum Phase (NMP) behaviour of rudders

•Inertia resisting movement in yaw is much greater (or “slower”) than inertia resisting movement in roll

•Initial response to a “step” rudder input will produce an initial roll in direction of the input (“faster” dynamics in roll than yaw, acting upon high frequency)

•Steady-state response in roll is heel opposite to rudder direction (“slower” hydrodynamics induced in yaw resistance dominate)