Research On The Active Pendulation Control Of Davit For Lifeboat Under The High Seastates

The sea rescue security system is a reflection of the overall strength of a country’sMarine. As an important part of the life-saving equitment, whether the davit can worknormally under the current sea conditions is the key factor which affect the workingefficiency of rescue ships, engineering ships and military auxiliary ships. The pendulationcontrol system installed on the davit is used for solving the problem of security andefficiency of offshore operation durning the process of folding and unfolding a life boat.Though the hydraulic cylinder piston’s translational motion adjusted by the controller, it canmake sure that the end of boom always keeps a vertical state in order to restrict themovement of rope and boat and prevent pendulation.The main purpose of this paper is to analyze the working principle of activependulation control system and then to find out how the system working actually on thebasis of the mathematical model of pendulum which is disturbed by waves and thekinematics model of the crane which established according to the theory of roboticscoordinate transformation. At last, based on the model, we design the appropriateclosed-loop control algorithm for the whole system. So the most important point is how todesign a controller which has the best anti-sway effect on the basis of reasonable payload.Through the analysis in the paper, swing model, boom kinematic model and as well as thewave disturbance patterns, all of these models are the main factors which will affect thecontroller’s parameters, so we should take all of them into account when setting controller.All of these which mentioned above will provide a theoretical basis and guidance forhydraulic system design.In this paper, we first introduced some basic background about davit, such as thedevelopment of davit technology and some applications on the real ships, the history ofpendulation-control problem and how to choose the right davit according to seastate. Andthen reduced the boat to a mass point, from the point of view of generalized energy,analyzed law of wave motion and also davit’s structure. Based on these, we established themodel of boat’s3D swinging motion, as well as the model of closed-loop pendulationcontrol system, so as to obtain the full model of the system for analyzing. Next, use themethod of forward and inverse kinematics to analyze the position and attitude of the craneboom in the space, which is the basis for designing controller. At last, chooseMATLAB/Simulink for system’s simulating. According to the simulation curve, we can get the information that how the swing angle changes when system is under the open-loopcontrol or closed-loop control which is based on the adaptive iterative learning controlalgorithm, and also the location of payload(boat) relatived to inertial frame. All of theseresults demonstrated that the active pendulation control system could reduce amplitude ofpendulation to the minimum and also the swing angle could reach the required range.