Anti-roll Gyro Stabilizer Design And Control For Ships

Ship rolling in random waves is a main factor which adversely impactsseaworthiness, safety, function of onboard devices and comfortableness of thepassengers. Especially for warships, the combat power will be severely affected byship’s rolling. Much efforts have long been done to suppress ship rolling effectivelyby the academy and industry. This paper is based on the background of the nationalscience and technology major projec（t2011ZX05056-003）. As a part of this project,its main objective is to measure the motion of the ship and attenuate the ship rollingeffectively.Firstly, this paper summarizes the development of the design and control ofgyro stabilizer for ships. And the nonlinear dynamic model for ships in rough waves isestablished. The structure and the operating mode of the gyro stabilizer is designedand the mathematical model is established.To obtain accurate6DOF ship kinematics in a variety of conditions, which isnecessary in the control of gyro stabilizer, a methodology is proposed which utilizessix accelerometers and three angular rate sensors. And the solution of constructingquadratic integral FIR numerical filter, which is very important in inertialmeasurement, is presented at the same time. The fundamental characteristic of theproposed filter is investigated in the frequency domain using the transfer functionsand accuracy function. And the validity of the proposed filter is demonstrated througha numerical simulation study and a lab experiment.The control algorithm is the key point in gyro stabilizer design. According tothe joint dynamic model of the ship rolling and the gyro stabilizer in random waves, avariable control gain method is utilized to control the precession angle of the gyro, sothat the desired control moment can be generated and the ship rolling will berestrained effectively. Taking a fishery administration ship as the research object, theeffectiveness of the controller to suppress the ship’s roll motion is simulated indifferent sea state. The simulation results show that the gyro stabilizer can attenuatethe ship roll motion effectively.To get a more efficient output moment to suppress the ship’s roll motion, a L₂gain controller that based on the backstepping method and input-output linearizationof the dynamic system is introduced with adequate consideration of the ship rollingmodel, the nonlinearity of the gyro stabilizer and the unpredicted rough waves. Aconstraint condition of restoring moment item is added into the L₂gain controller tobind the gyroscope precession angle in a certain range, so as to avoid the precessionsingularity. Numerical simulation of an actual ship’s rolling state validates theeffectiveness of the controller on suppressing the ship’s roll motion under randomwave excitation and restraining precession singularity.